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MG TD TF 1500 starter cable HOT + smoke! Help. BBS discussion at MG-Cars.net
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MG TD TF 1500 - starter cable HOT + smoke! Help.
| Hi all, I decided to give my new wiring a shot. I couldn't resist. First time I turned the battery "kill" switch to on position I see a puff of white smoke from somewhere near starter switch. I hear a few clicks (not fuel pump, ignition key is turned off). I kill it instantly. Reaching under the dash I touch the starter cable. It is very hot to the touch!! I've read about starter switch failure in archives but this switch has never been a problem and the rubber insulators on it's terminals are very good. But obviously the current from the battery to the terminal with the 2 brown wires is somehow running down the metal cable itself. I rigged a simple 1.5V battery to a multi-meter and it shows about .25 volts when I touch the cable! The switch seems a sealed unit or I would investigate further. Before I burn the car up can anyone help? Is my switch bad? Source of white smoke puff - what burned? Thanks in advance, Ed |
| efh Haskell |
| Hi Ed. I don't know the source of your smoke, but it might be an idea to hitch up a battery charger as a source of 12v instead of the battery while testing. This will provide sufficient power for some testing, but will have a cut out or fuse which will avoid frying anything is you have any short circuits. Matt |
| Matt Davis |
| Ed, It sounds to me like your terminals or switching inside the switch is shorting to ground and the starter cable is acting as the ground return. You can put a 10 amp fuse between the battery and the power cable. It will let you do everything but turn the starter motor. Also look for a bad ground at the engine or chassis. The braided line from the battery to the tub MUST have a completely clean connection including removal of all paint, etc. Then, coat with dielectric grease to prevent moisture and dirt from attacting the bare surface, and then tightly connect the ground. Ditto for the braided strap from the chassis A-tower to the gearbox/bell housing. Both connections must be bare metal and dielectric grease must be applied. I know it sounds counter intuitive to use a non-conductive grease, but it is there to prevent moisture intrusion. The act of tighting the connections will be enough to drive it from between the surfaces protected. Warmly, Dave |
| Dave Braun |
| Dave, let me ask you this. My wife noticed the interior starter cable was indeed separated from it's exterior "housing" cable and was indeed touching the firewall where it comes through (why no grommet there?). I told her this was just cosmetic and I would fix it when I installed the cable "for real" (when I finish the dash panel). Are you saying this interior cable actually picks up the electricity through the firewall (a "ground return") and heats the cable up? If so, WOW! There are lots of metal things that touch the firewall. Wouldn't they all heat up? (Pardon my lack of electrical know how!) And what made that ticking sound? Maybe sound of arching between the cable and firewall? Would that make a little smoke also? Not sure I understand where to put that 10 amp fuse? You mean between "+" terminal on battery and big cable going to starter switch? (Remember I have neg. earth.) And Matt, I don't have a charger (and Dave can't believe it!) |
| efh Haskell |
| Afterthought: And as a test I guess I could just remove the starter cable and try again? If everything works I've found the problem?? (If not the car burns up?) And yes, I've done the grounds per your website Dave, including the grease. Only ground not connected yet is the black wire going to instrument cluster. I've read it's there just to ground the panel lights which I'm not worried about at this time. Maybe it's time for a vacation? Leaving Sat for a 2000 mile drive back east to visit son in the Army near Savannah. Anybody near there? |
| efh Haskell |
| Hi My twopenneth worth thinks that the return spring and or the moving contact insulator or both have broken allowing the moving contact to touch the the main live terminal then finding a return to ground via the central shaft and starter pull cable. Try disconnecting the two main cables and bridgeing with another switch or solenoid and connecting the main loom brown wires via a fuse as Dave suggested.Happy hunting |
| B A Robson |
| ed, what failure mode do you think the starter switch would have to cause this problem? to me the switch is open or closed..if closed the wire to the starter is energized. if it fails open the starter wire gets no juice. for a cable this size to get that hot that quick it like the wire that is hot has a dead short or the device it is connected to is a dead short. if the wire is disconnected from the starter switch and isolated, what happens. i do like matt's idea about taking the high AMP battery out of the circuit and using a charger to troubleshoot the wiring. have a good trip ed. my thanks to your son for his service to our country. regards, tom |
| tom peterson |
| Ed - I answered your question about the fuse in a separate post. The smoke and hot starter cable is probably the result of a bad or no connection from the engine block to the frame of the car as Dave B. suggests. Further, I suspect that you have a wiring harness problem somewhere that is drawing a lot of current - possibly a starter switch stuck in the on position. Cheers - Dave |
| David DuBois |
| Ed, The ground recomendations are Dave DuBois', I can't take credit for his work. The starter cable is basically connected to the housing of the starter switch, which in turn is grounded to the tub. The Power terminals, both in from the battery and out to the starter SHOULD be isolated from the switch housing, both internally AND where the lugs attach to the terminals. However, if one of the terminals is shorted to the housing (since you didn't energize the power starter switch I'm gonna assume that it is the battery lug side that is shorted) AND the starter switch housing is effectively isolated from the tub with a nice thick coating of paint, the starter cable will provide a ground return for the short. Even if you haven't grounded the instrument panel, it is possible for the current to find its way to the ground side of the battery by sneak currents and the like. Hope this helps explain, dave |
| Dave Braun |
| David, the enging->frame ground is brand new and seemed to do it's job during engine run testing a few months ago via a test rig (see Youtube.com). And if the starter switch was stuck on the starter motor should have turned but it did not, nor did I ever get that far. And the starter switch has no ground wire to the tub that I know of. Should it? It has the wire going to the starter motor which is itself grounded to the block of course, which is grounded to the chasis via cable. Why would the switch need a ground? I'm gonna try it with the starter cable removed tomarrow. Thanks all! |
| efh Haskell |
| I'm with the Davids- sounds like one of the two problems or a combination- bad/shorted switch and or bad ground somewhere. The battery ground must be perfect to the battery box, and then to the frame and via the braided cable to the engine. For the cable to get hot, a lot of current must be flowing through it. However, if the switch wasn't pulled and it heated, has to be an internal short in the switch. George |
| George Butz |
| Is there a way to open the starter switch to inspect inside? Okay, here's the stupid question of the day. Please bear with me. I'm not an wiring guy! How come I don't get a shock if I touch a bare wire to a bare place on the tub or chasis of a running automobile? Isn't there electric current traveling there via various ground cables on it's way back to the battery? Or would I have to touch the other end of the cable to the battery to complete a circuit? (I told you this was stupid!) |
| efh Haskell |
| Ed disconnect all the leads from the starter relay switch and see if you have any continuity from either of the lugs to the switch case. If you do there is a short, replace it. Mike |
| Mike Hart (52 TD 16378) |
| hey ed, perhaps i'm a half an electron off, but the only time i have had a big cable get instantly hot is with a dead short. i am anxious to hear wht you find. regards, tom |
| tom peterson |
| Hello If I read Ed,s 1st post correctly he said he reached under the dash and grabbed the starter cable? .Am I correct from that position you would only access the the starter pull cable not the main or sw to starter cable. This lead me to the explanation of the internal short in the switch grounding possibly via the pull cable if it was that that got hot, even though the pull start had not been used. You won,t get a shock doing the grounding of the wire but you may get burnt fingers or worse if not fused a major meltdown and a fire be careful if you dont know about electrics dont play, it can bite in other ways |
| B A Robson |
| Ed, just looking at the wiring diagram and thinking that maybe you hooked the brown wire coming off your ammeter to ground inspection socket rather than the hot post or possibly your hot inspection socket is grounded. You have two brown wires #33 attached to the starter relay. One to the fuse at A1 the other to the ammeter at the same connection to your red inspection socket. Mike |
| Mike Hart (52 TD 16378) |
| The only way to open the starter switch is with a hacksaw. No need to open, use your ohmeter to check for continuity between the terminals and case- there should be none. To create a "shock" or spark, there has to be a current flow, at least at 12V; a bare wire would have no current flow, etc. There may be a good one if you touch a high tension power line however! Suggestion: google 12V electical theory. There are a bunch of great articles that explain it really well. Once you understand it, it would make troubleshooting a whole lot easier, and greatly minimize the chance of the Lucas smoke escaping. Still skiing? George |
| George Butz |
| B A, i see what you are saying. i misread ed's post. thanks for the heads up. regards, tom |
| tom peterson |
| Ed, My money is on "dead short" as well. (starter switch?) ...test it "out" of circuit. IMHO: Best advise here was "disconet battery and test with a charger"...lower amperage and circuit breaker will be well worth the cost of one. The high amperage of a new battery can turn your project to toast in short order. A dead short can act as a (very unwanted) welding outfit. Be safe, and keep us up to date. David |
| David Sheward |
| Ed, My money is on "dead short" as well. (starter switch?) ...test it "out" of circuit. IMHO: Best advise here was "disconet battery and test with a charger"...lower amperage and circuit breaker will be well worth the cost of one. The high amperage of a new battery can turn your project to toast in short order. A dead short can act as a (very unwanted) welding outfit. Be safe, and keep us up to date. David |
| David Sheward |
| Thanks one and all. I've read up on electricity a bit more and have done resistance check on the switch removed from the car. The results are "OL" (over load) when checking from either post to the case of the switch, meaning no current is passing between these points, which is good. I used numerous points void of paint, etc. I get about .2 ohms on the terminals themselves which seems reasonable. I get OL between the 2 terminals unless I press the pin with a finger to close the circuit. In other words my switch seems fine which makes sense because I used it to test start the engine several times a month ago! So what is left? My grounds from battery to firewall and engine to chasis are brand new, cleaned of paint and have dialectric grease and are very tight. I have no ground to inspection socket at this point because I don't have an inspection socket! Never did - PO removed it I guess. I'm going to try to find a charger today before going on. Will advise. Let me know if you think of something else please. Ed |
| efh Haskell |
| See if you have continuity between either one of the switch poles and the switch case and the poles and the cable pull pin. |
| LaVerne |
| LaVerne, that's what I was trying to explain in last post but I guess I wasn't clear. I have zero continuity between any of those points, which I take to mean the switch is in good shape, right? |
| efh Haskell |
| Ed, Just a few random thoughts - is the switch an original Lucas, or a replica? Quality control is poor on many replicas! The same switch was used on lots of British cars and used examples are common over here - no use to you I appreciate. Following on from George Butz, I agree it is unlikely that you will need to open the switch, but if you do the edge can be carefully peened back from one side and an end, and removed and replaced - I've done it to renovate several switches. The large contacts were originally insulated from the body of the switch by rubber sleeving which rotted over the years. Later Lucas switches and replacements were insulated with plastic that was longer lasting. I've renovated this vital area with the clear plastic tubing supplied originally to protect the thread of a new NGK spark plug inside it's box. It's just the right size to slip down the contacts into the switch, once the old rubber is removed. It is possible that a meter will not reveal an intermittent short, but will fail with the large ampage resulting from the starter being used. Hope this helps John |
| J C Mitchell |
| Ed, I think OL on that meter means Open Load, not Overload. I'd think Overload would indicate a short ckt, but you say you got OL between terminals until you pull the cable, and also from either terminal to the case. If that's correct, then it sounds like your switch doesn't have an internal short to the case. And that doesn't explain your problem, unless it's an intermittent short to the case. A month ago, IIRC, you had the switch mounted on a board, so if it did have an internal short to the cae, it wouldn't matter. Al |
| A W Parker |
| Try checking the switch while pulling the shaft and wiggling the terminals around at the same time. This would ensure that nothing is shifting or moving and shorting from the force of pulling the cable. |
| George Butz |
| Ed Because the multi meters use a low voltage source for checking resistence you may find that it will not give an accurate test if the dielectric (insulation) is only doubtful? Another check may if you have test light in series, with in your case 110v ,as the voltage source ,and then check with the two wires(test leads), that would be into the normal light switch one to ground the other to to each terminal this should provide enough voltage to achieve condinuity thru any fautly insultion.Remember to isolate the wiring loom connections from the s/sw to protect the low voltage items IE bulbs flasher unit etc.Hope this is not tech. Blair |
| B A Robson |
| I just purchased a cheap "computerized" 2,4, 6 amp Schumaker charger from Walmart. It does trickle, medium, and fast charges. Low amperage, not meant for jump starting. Sounds like what I want. Instructions say to connect it to a battery and it will "detect the presense" of the battery. Humm...before I try it without a battery can someone tell me if it will even turn itself on if no battery is present? If not, what good will it do me? Al, I got "over load" jargon from a web site. It meant a totally broken circuit. I agree, it's confusing jargon. Also, I did have it on a board but I also had the cable attached thinking I would use it but never did - too much trouble. I didn't notice hot cable then but I guess I would not have since it was bolted to the board as well? BA, I think you're saying to use house current and a test light as a better test than ohm meter. Humm...let me think on that. George, nothing wiggles. John, I believe it's a Lucas. Thanks again, Ed |
| efh Haskell |
| Hi again Ed, No, the pull cable (I think that's the one you mean) wouldn't get hot unless it was grounded. Be very careful messin with house voltage, from what you've said you'd better forget that method, too easy to hurt something, incl. yourself. The charger might not turn out without a battery but give it a try. Al |
| A W Parker |
| Apparantly this charger won't work without a battery connected to it. There is a led that is supposed to light up when it detects a battery present. It does not light up. I connected the charger's black clip to my battery ground cable which connects to battery box and it's red clip to the power cable going to the starter switch. I did NOT connect the cable from other side of starter switch to the starter for fear of the unknown! I then connected a test light from hot starter switch lug to chasis. No light! What am I missing here guys? What kind of charger do you guys have? |
| efh Haskell |
| ED, I believe you have your battery charger hooked up incorrectly. If your car is positive ground, then the red lead from the charger should be connected to the car's ground cable and the black lead should be connected to the starter switch. Cheers Phil |
| Phil Atrill |
| It's neg. earth Phil. Good thought though. Thanks. I also have a simple trickle charger. I wonder if it would do the job? One way to find out I guess... |
| efh Haskell |
| ed, this doesn't help with your problem, but i am curious, did you convert your car to neg earth or the previous owner? regards, tom |
| tom peterson |
| PO Tom, except for the alternator which always read backwards. |
| efh Haskell |
| Just checked the archives (again). There are lots of folks out there who have used a battery charger to test new wiring. Can a few of you please tell me what make/model of charger you have and if it has a "battery detect" feature? Maybe older chargers don't care what they're attached to? I just plain stuck - no progress...you know the feeling. Thanks, Ed |
| efh Haskell |
| Trickle charger doesn't work either....sigh. |
| efh Haskell |
| Can you find an old analog multi-meter- the kind with a movable needle? There is no doubt whether no continuity or a short. I have had the same trouble you had with a digital ohmeter- the OL vs. just 0. Hard to tell if no resistance (closed circuit), or no continuity. Have to find an old non-digital battery charger to use that method, mine are ancient. Or rig up a test rig with a bulb and a couple AA batteries. If a Radio Shack is nearby they have that stuff, and maybe a needle-type meter. Or something like this: http://www.chain-auto-tools.com/electrical_auto_tools/MET026L.htm George |
| George Butz |
| Hi ed Just a reference to A W Parker (Al) comment on the pull cable grounding . If the Dash is earthed as it should be due to the need for dash items to operate the pull cable wire wound exterior will be at ground potential as this is secured into the dash by the nut& washer located behind the dash Rgds Blair |
| B A Robson |
| Blair, the dash is not finished yet. The pull cable is just hanging loose behind firewall for now. |
| efh Haskell |
| Ed, When this happened was the starter push/pull cable attached to the dash panel? Is the push/pull cable touching the bulkhead metal where it passes through to the switch or through the rubber grommet? How much of the wiring is connected? Is it possible you had a hot unconnected wire end touching the cable behind the dash? Mike |
| Mike Hart (52 TD 16378) |
| Mike, no it was not attached to instrument panel. It was draped over the support bar under the dash which I realize is indeed metal. My rubber kit came with no grommet for that hole either. I had no unconnected wires. I am sure of that. I just purchased a new multimeter with a built in beeping continuity testor. I'll be testing for shorts today. I gave up on using the battery charger. Wish me luck! Ed |
| efh Haskell |
| Ed, Any chance the starter got hooked-up wrong? Aslo make sure the 2 brown wires to amp meter are disconnected and "isolated". You said that one was "reading backwards" so when you put it back in the circuit swap them and you should be good there. Think I would disconnect everything at fuse box to start tracing. Using your new meter don't forget that you will get some "resistance" checking many of your components. (lights ect) Wish you were closer ...I feel your pain! Cheers, David |
| David Sheward |
| David, "make sure the 2 brown wires to amp meter are disconnected and "isolated"." Why would I want to disconnect these? By "isolated" you mean not touching anything I assume? Starter motor installation is untouched since my test engine run a while back. Worked fine then. Okay, 3 new results using my new meter with continuity test buzzer feature. Battery is removed and meter is replaced in it's stead: 1. Ignition key OFF/jiggle wires anywhere/"short" displays on screen + beep. I tighten the 2 ground cables at regulator. Seems Fixed! One down, I hope! 2. Key OFF/close starter switch with my hand/short displays again. Is that normal? 3. Key ON/short displays immediately. Remove either of the 2 wires at ammeter. Short goes away! I reverse wires at ammeter. Short displays again! Something wrong with ammeter?? Worked fine for years though! (Note I do not have the wire from ammeter to inspection sockets because these are MIA on my car.) Suggestions? Ed |
| efh Haskell |
| More testing results: 2. (above): I disconnect wire from starter switch to starter motor. I then connect car battery directly to starter motor with jumper cables. Motor turns over perfectly. Humm...? 3. (above): One of the ceramic connectors into which the bolts thread that hold the brown wires on was broken. A chunk of ceramic had broken off, I assume from PO overtightening it. I simply glued the broken piece back on with super glue a few weeks ago. If I totally remove the ammeter from the system the short goes away however! Could there be more to this broken connector than I think? I don't have another one or I would use it of course. |
| efh Haskell |
| Ed, have checked the wire going from your ammeter to the inspection socket form the ammeter? It could be hooked up to ground side socket. An easy mistake. Mike |
| Mike Hart (52 TD 16378) |
| Mike, I don't have an inspection socket hence no wire going there. Worked fine for many years that way. |
| efh Haskell |
| After following the above, I think the problem was initially that the battery cable terminal to the starter switch was making contact with the starter switch case. Thus high current to ground thru the pull cable when the cut off switch was closed. The starter switch originally had rubber insulators (later plastic) to prevent the battery cable terminal or the starter cable terminal from touching the starter switch case which is grounded by both the switch bracket and the pull cable. Your readings of "NO RESISTANCE" = almost zero, when looking thru thru starter (ie: one lead on ground, the other on the cable to starter or to the two brown wires with switch on) is simply measuring the total resistance of the starter or the ignition circuit, Both of these should be low. So what you got is to be expected! I would replace the starter switch in case of internal damage, reconnect everything and start over. |
| Don Harmer |
| Hi all, I agree with Don's explanation for a likely short - it's what I suggested in the third para. of my previous comment! All I was pointing out is that those with original rubber insulated terminals should check them out, modify or replace, to avoid a potentially dangerous short. Hope you sort it Ed! Cheers John |
| J C Mitchell |
| Ed, Sounds like problem might be in the starter switch (as others said). My reasoning behind "isolating the amp meter leads" is pretty basic ...it is one of the few wires of a heavier gauge in the system so is a strong canidate for doing some serious damage. (a thinner wire will act as a "fusable link" and "fry" if a direct short is present). Not a pretty thing ...but far less damaging. Since your kind of new to this wiring stuff...kind of keep in mind the simple concept that the thicker the wire the higher the potential for serious damage. (rule of thumb) I was also wondering if there was the possiblity of the amp meter having a bad isolator and putting voltage back into your ground plane. Really wish I were closer ...not a very good mechanic but pretty good at wiring. |
| David Sheward |
| Guys, I appreciate the ideas but the switch is perfectly insulated externally and passes resistence tests internally to the best of my ability. I wish it were that obvious but it just isn't. I'ld gladly buy a new switch! Still testing with new continuity testor. Will advise when I find it. Thanks again, Ed |
| efh Haskell |
| Status report: I cannot find any real "shorts" using the meter. So yesterday I carefully put the battery back on the car leaving the hot brown wires out of the system at the starter switch. I also leave starter pull cable out for now! I press starter switch with finger and starter motor cranks just fine! I add hot wires back. Using test light I have power to fuel pump, coil, all lights, etc. I don't know what I did, but it's working. I show no power on starter switch case anywhere, only on the hot lug where it should be. But for reason's I cannot say I temporarily had removed the wire from dizzy to coil - paranoid I guess. I reach down (with ignition still on) and replace it - BUT TO THE WRONG TERMINAL. I stuck in on the same coil terminal "sw" the #9 white hot wire attaches to (it had 2 tab connectors). In horror I watch as the hot white wire from coil to fuse smokes and insulation starts to melt on #9 in front of my eyes! I quickly shut down! I then cry. My wife leaves garage quickly. It's a short wire and can easily be replaced, albiet not through the harness. I retest this morning and everthing seems OK - power to all elements tested yesterday. I hope I haven't fried the coil or dizzy? Any suggestions or way to test these? I did remove dizzy cap and it may smell funky in there, not sure though? Tomarrow we leave town for a month to visit our son in the Army back east. He's getting married before his next deployment, whenever that may be is unknown. So I'm gonna wrap up this thread as done! I never expected it to go on like this and thanks to all of you for your input!!! I think a fresh start in a month and I'll get this thing running yet. Ed |
| efh Haskell |
| OMG Ed, how terrible that must have been for you as you see the heat, smoke, and all. After all you've done to solve this problem, I can easily feel your pain at what you experienced yesterday. Yep, best to let it go for now and enjoy your trip back east visiting with your son. Kind of puts the important things in life in perspective, right? Hopefully, no serious damage was done and you will quickly finish up this phase of your restoration upon your return. Have a safe and enjoyable trip -- John |
| John Brickell |
| Say hello and thanks to your son from a WWII veteran. I'd love to shake his hand and hug his wife for his service to his country. God Bless Bob |
| Bob Jeffers |
| Safe jorney to you and a "thank you" from me to your son for his service to us. David |
| David Sheward |
This thread was discussed between 04/04/2011 and 08/04/2011
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