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MG TD TF 1500 - Generator # seven? (Any-ideas?)

If anybody else has been folling Grace & John on their journey…
http://driveawaycancernow.org/
…any ideas on what could be causing this?

They have been through 7 generators, a bunch of batteries, voltage regulators, and still having charging problems.

This dynamic duo is in Louisville KY. Right now and headed my way for an oil change in the next few days. Given the “shape” of the car I’m wondering if lack of a good ground or a dead short could be causing the problem? (From what I gather it’s burning the bushings out). I’m not “too bad” at wiring and would love to be able to find the fix
this for them. Could something as simple as bad ground cause this?

I know this isn’t much to go on, but if anyone here has some ideas about what we could look at please let me know. Not sure what kind of schedule they will be on so it would be a big help to have some ideas (check list) that we could move through in the hopes of getting this right for them.

Thanks in advance for any help here!

Anybody have a voltage regulator for a 53 Austin 100 they want to donate to the cause?



David Sheward

yes, I'd think a bad ground could be a major contributor.
If he's losing bushings also, perhaps the belt is too tight.
Al
A W Parker

He has had several very good mechanics replace the genny's, and pretty sure belt tenson has come up before.
I'm wondering if the "smart guys" are simply overlooking the obvious.
Somestimes being dumb and having driven junk most of your life can be an advantage!
I have had a wiper motor for a 92 Dakota for sale on CL for years. Have had it "sold" at least 5 times.
Everytime they show up I get out the dremal tool, grind a spot on the firewall and run a ground to the wiper unit and a selftapping screw to firewall.
Haven't sold the motor ...but made a lot of friends!

Noticed in some of the pics of the car a "blank spot" on his dash. Wondering if that is where an amp meter should be and what effect not having it connected could have?
David Sheward

Dave, you may have hit it. I seem to recall that on my 77B the ammeter was a critical component. Where can we find a wiring diagram for the Healy? Bud
Bud Krueger

Bud - Your 77 MGB had an ammeter???

Dave - The only thing that jumps out at me is your statement "(From what I gather it’s burning the bushings out)". If it is bushings and not brushes that are being destroyed, then he is running the fan belt tension way too tight. Cheers - Dave D.
David DuBois

Too tight a belt was my first thought when reading the postings about the troubles. Had some brief conversations with John about that and pretty sure he is aware of "correct tension". He is no stranger to British Iron ...races a vintage TR.
Not real clear on "bushings or brushes" issue info on facebook sketchy at times.
Real hard to believe as many people that have looked at this nobody has come up with more than a temp cure.

If the amp meter is missing should the wires that would go to it be connected ...or issolated? Or should they be running through some resistance to emulate a meter? Fist thing that comes to mind (to me) would be perhaps a large resistor like one use for a coil?
David Sheward

Gents,

If a Healey is like most cars of the time everything but starter current passes through the amp meter. Therefore the disconnected wires should be joined and insulated. It would be a great gift to install an amp meter from Auto Zone or equal. My guess is that if you could watch the amp meter while driving you would see instantaneous discharge under some circumstance of bumps, resonance, hard turns or who knows what. Even moving ones feet in the cockpit if wiring is exposed. Nearly burned down a new Ford of that era because they ran the main feed through metal clips with only the wire's insulation as protection. The generator died and we smashed the end off the battery for lack of a wrench. A close examination of the main feed (through the amp meter where ever it passes through or near chassis ground would be my first try at a fix.


Best regards,

Jim Haskins

1953 TD
J. M. Haskins

Jim,
Good idea with the meter. Not sure if that is what is missing from the dash (hard to remember the layout as I sold my 100 in 1970) but think I'll pick one up just in case. Can always take it back if we don't use it.
Thanks
David Sheward

Dave D., you're right as usual. It's been a long time. Now that I think of it, it had an alternator. Now I'm even more puzzled about the charging system. Bud
Bud Krueger

I don't believe the AH BN4, BN6, 100-SIX series ever had an ammeter. Here is a shot of the wiring diagram, which might help to sort things out.
Cheers Phil


Phil Atrill

David-
Send me an email and I will send my all encompassing diagnostics procedures, AKA "Electrobabble".
Suggest check/replace main battery cable to solenoid, basic grounds as detailed.
Suggest no ammeter, but a voltmeter, wired D regulator to earth. That will show what the generator is seeing.
Something is murdering these things!
And send your location and the schedule. I might come down, think you are about 150 mi.
I have names to write too.

FRM
FR Millmore

Spent the morning looking through the Moss catalog for the Austin. Noticed there was no amp gauge! Thought about voltage gauge but everything I found on the auto parts shelfs today seemed to have a built in shunt and for neg ground only. Not sure if Grace is poss or neg ground. It was fun being laughed at all day asking for an "amp gauge". Told them to "think old school" and most looked out the window and assumed it was for the TF in the parking lot.

Then it hit me ...duh .."think old school yourself dumby"...get out of the auto parts stores. Tractor Supply had a nice 30 amp meter for Ford tractors at $10. (pix)
If I am correct should be fairly easy to hook one up as it does have appear to have an external starter solenoid switch. Should be easy enough to put this in line from there to/from the wire to ignition switch.

Phil,
If you could send that diagram to my email in higher resolution than allowed here it would be a big help.
hootersvilledavid "at" yahoo "dot" com.

FRM,
I'll send you an email.
Not sure when John & Grace will be here but will post the ifo soon as I know. The more the merrier.

I am getting quite a list of names together if anyone here has someone to add drop me an email and I will try to get it done for you and send back a picture of them on the car.
David Sheward

oops ...here's the gauge I picked up for $10.


David Sheward

David-
"Thought about voltage gauge but everything I found on the auto parts shelfs today seemed to have a built in shunt and for neg ground only."
That's how voltmeters work. They measure voltage across a known very high resistance at very small current flows (c 1mA). Polarity makes no difference except you hook them up backwards, so if there are two terminals you are good. If it only has one insulated terminal, then it is measuring to a case ground and is no good. I just looked at one that does in fact use the case as ground - stupid!
Another reason to convert to neg earth.

At worst, a cheap ($10)DVM can be wired in, and with a spare set of leads is otherwise useful on road trips.

Ammeter does NOT go in IGN feed. It goes in Bat (solenoid)>Reg feed, or can be put in Gen D >Reg D to read generator action direct. Ammeter carries full system load, so wires MUST be BIG. Ammeter reads voltage drop across a known very LOW resistance.

FRM
FR Millmore

Took my meter with me today and every one I encountered had 1 post tied to case!
Not knowing if Grace is p/n ground decided maybe not a good way to go.

Reading through "Electrobabble"....Great stuff, we think alike ...but I think your smarter and more experanced than I. I will have questions ...will there be a test? LOL

Not real sure where Grace is ...earlier the map on ebay showed them north of Indianapolis ...but just checked and looks like still near Louisville.
David Sheward

Is he doing alot of nighttime driving; running with some non-origional headlight bulbs? Halogens might be drawing alot of juice, which over time will tend to cook generators. Just a thought!
Steven Tobias

Thanks Steve,

My best "guess" is a bad ground or intermitten short for now. (Car came from the "rust belt" i.e. MI.
That's not a slam on MI from someone living in OH.
OH is in the rust belt also!)

Untill he gets here and we can take a look and ask questions, keep the ideas comming. I am making a list!
The longer the list the better chance of sucess is my hope!

Fletcher has come up with a great idea for hooking up the amp gauge as a "diagnostic install".
David Sheward

As I understand it, Lucas ammeters used the magnetic field around a wire, that's carrying current to move a vane tied to the needle. Inside the ammeter there is just a few turns of heavy gauge wire. The description above about the ammeter reading the voltage drop across a low value resistor is correct for a laboratory instrument but not correct for a dashboard instrument.

The accuracy of the dashboard ammeter is so poor that they can only be used to tell which way the current is going, into the battery or out of it. In fact the owners manual for late LaSalles made that very same statement.

I'll get off my soapbox now. Thanks for reading.
Cheers,
Bob
Bob Jeffers

Bob,
Fletcher and I have been conversing about this one off-line a bit. Don't think he will mind if I put some of the conversation up here so he doen't have to type it out again:

Scheme A) Normal ammeter install is in wire from solenoid to Reg A. This reads all power in or out of battery. = operational install.
Since the car will run with the battery removed, powered by gen, this meter will not tell you what the generator actually sees. It will tell you that the gen is not working, and the battery is discharging. It will tell you that the battery is charging some amount, say 15A, but does not tell you that the system is loaded at max by equipment drawing 25A, so the gen is making 40A = meltdown.

Scheme B) In Wire Gen D to Reg D, it shows only power out of gen, and should never show a discharge. = diagnostic install.
If discharge is shown, the reg cutout has stuck - a common issue in the old days, and the car is not running, or the gen is otherwise kaput. Common reason for sticking was an overload that pulled enough juice through the cutout to weld the contacts closed - ie a dead short somewhere. Gen will attempt to run as a motor, killing the batt and maybe the gen.
This one tells you what the generator sees, and that "something" is connected, but does not tell you what the battery sees or does. It will tell you that gen is making 15A with nothing ON, a regulator fault if the battery is fully charged. Or it will show you that the gen is making 40A with a full system load, same meltdown. Or it will shows vicious spikes. But it will not show you that the battery is discharging, unless it is through the melted gen.

As a "tool" to possibly track down an intermitten this makes sence to me. Given the number of people that have worked on this car it's hard for me to believe it is a "constant" problem, but rather something intermitten in nature.
David Sheward

I won't argue Bob's description of the Lucas ammeter. I don't know that I've ever thought about it, and I am already too far behind where I should be to go crawl around to look at one. I have examined and dissected automotive ammeters which have a big shunt resistor across them, internally or externally, so Bob's description is not valid for all.
And while I agree that these meters are not top quality instruments, anything that killed 7 gens + batteries + regs ought to show up someway.

FRM
FR Millmore

This thread was discussed between 19/06/2012 and 23/06/2012

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