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MG TD TF 1500 - Sollid State Regulator

I have a solid state voltage regular in my 1952 TD, that I got from Bob Jeffers, and it has been working fine until today. I had my starter repaired and installed it, hooked up the battery and turned on the key and I noticed that the amp meter was reading neg. I started the car and the needle would move a little to the middle. I turned off the engine and turned the key back on and the needle moves way to the left. Can anyone help me?
Oh by the way I did email Bob and asked for his help, have not heard back yet.
Thanks in advance.
Louis
TD17600
L.M. Levin

Gee....thats what mine does...? Once it starts, if the battery is down, it moves further to the + ... if it is charged it stays in the middle?
gblawson(gordon)

"key back on and the needle moves way to the left" I assume you mean an extraordinarily large move left.
That sounds like heavy draw. Didn't have lights on, did you? Any wires get super warm and toasty?

The fact that the needle moves to the right after starting would indicate generator is contributing something. Sloppy belt might account for inability to move over into charging side but a nasty draw could keep it in the discharge, too.

Does revving boost it to charging or not?

It returns to zero with the key off? Right?

Are you using the pull switch or starter solenoid?

jrn Northrup

Louis - We can sit here and make guesses until the cows come home and not be right. The only one who can really help you is Bob. Not only did he make the regulator, he is the resident expert on the charging system. Be a little patient and wait for an answer from Bob. Cheers - Dave
David DuBois

Louis, if the regulator was working , and the last change was the starter, I would double check this possibility. Disconnect the starter connection and turn the key on to see if the current draw is as heavy.

The starter connection itself can be tricky as it is insulated from the housing, but can turn and twist the internal wires if not backed up with a second wrench.
There is also the possibility of a bad repair.

Dallas
D C Congleton

Thanks guys. I have heard from Bob and will be sending the reg. back to be checked. I also am going to have the starter rechecked. Jim; The reving does cause the needle to move toward the middle. Yes it does move to the middle with the key off. I am using the pull switch to start the car.
L.M. Levin

The starter won't have anything to do with it. Since you have the pull switch, the starter is completely disconnected after it starts. That's one of the reasons I asked about solenoid vs cable.

This is really farfetched, but I've got to ask anyway... I realize the posts are different sizes, but you didn't hook the battery up backwards, did you? The original regulator will run on either polarity but I'm willing to bet the solid state regulator won't. I suspect the generator wouldn't charge at all with your regulator bassackwards. I won't cost anything to look at your battery cables.
jrn Northrup

Thanks Jim. I only installed the repaired starter and hooked up the positive ground battery cable. I only disconected the ground cable from the battery. Prior to having the starter repaired everything was normal. I am at a loss. Is anyone on this thread anywhere near Modesto, CA? if so maybe you can help me.
Louis
L.M. Levin

Louis - While you are waiting for Bob to check the regulator for you, you can check the generator to see if it is putting out sufficient voltage. For instructions on testing the generator, go to the article, Testing a Dynamo/Generator in the other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Just run the first part of the test, since you will not have the regulator installed to do the second part of the test. Cheers - Dave
David DuBois

If it wasn't for the fact that you have a solid state regulator, I'd have asked if you "polarized" the generator. Are there any installation instructions with the regulator?

When you turn the ignition switch on, about how many amps does it read in discharge? Ours moves barely 1/16" (or just a couple of amps) back and forth in time with the fuel pump. FYI, ours stays there in discharge at idle. Since your engine started, it would SEEM the fuel pump and ignition are functioning OK, and the old MG electrical systems only need those two systems to run. So how far does the needle move just turning the switch on with all else off?

There's a "discharge" idiot light. Does it light up?

What happens when you turn the headlight on? How many amps does it draw? (ours about the first ammeter mark, around 7.5A) Switch brights to dim then parking lights, OK? (our "side" lights barely a couple of amps). Check brake lights & dash lights, too. Identify any lights that do not come on.

Watch the ammeter and honk the horn?

Diagnosing the wiring system is a process of elimination... check these out for now.

I'm a long ways away in Michigan, but will be in Walnut Creek, CA in 2 weeks. That's still a bit of a drive. Hopefully you'll be up and running before that.

jrn Northrup

JRN: Here is the story, when I turn on the key the meter needle goes all the way to the minus 30. If I leave the switch off and just turn on the head lights the needle goes just past the 1st mark to the minus side. The "discharge" idiot light does not come on, Iput in a new blub and it still does not work.
L.M. Levin

A minus 30A reading looks like one helluva draw somewhere, if not a direct short. There ought to be a wire getting awfully hot.

I trust you're pulling off the regulator. Once it is removed, make sure the wires aren't grounding and switch the ignition on and see if the ammeter tacks over to the left. If the 30A drain is still there, then you can count on the regulator not being the cause.

It is hard to imagine the fuel pump could suck that much juice and still work, and surely that light wire couldn't last long, but go ahead and unscrew the wire from the front of the pump and see if that drain disappears.

On the same hand, it is hard to conceive the ignition would draw that much and still operate.

Your lighting circuit matches mine and is probably eliminated as factor.

It is 3:40AM so I'll continue this later tonight.
jrn Northrup

Thanks for the update. I will disconnect the regulator and see what happens before I send it in for a check up. Louis
L M Levin

Sounds like there is a near-dead short somewhere. Lucky no fire with that much draw. Above right on w/ fuel pump. I think the ignition, the wiper motor, and the fuel sender are all on the keyed circuit, maybe disconnect one thing at a time to find short? With the old-fashioned mechanical regulator, the "cut-out" could stick and cause reverse current flow when the car was off, no clue about the electronics. George
George Butz

I disconnected the voltage regulator turned on the key the amp meter did not move. The horn works and the car starts, no lights though. I am sending the regulator off the Bob Tues. so he can check it out. I am at a loss, will keep on checking.
Louis
L M Levin

Two issues haven't been discussed yet.
You say you have a '52 and I assumed it originally had fuses in the regulator like our '52, instead of a separate fuse block. Does it have a separate fuse block or did the solid state regulator incorporate them?
Secondly, there's no mention of fuses blowing or not. I assume nobody shorted across the fuse terminals. The "Operation Manual" says the fuses are rated at 35 Amps, so it is conceivable the current is running through the one fuse, but I have my doubts.

Once your regulator gets back, if the excess draw still haunts you, removing the fuses will narrow it down quite a bit. We should've done that first thing.

You said the ammeter doesn't move with the regulator out, that's what would be expected. The horn works (separate fuse block?)and no lights, I can buy that.

You said the engine starts. Did you mean it rolls over or mean it started up and ran?
jrn Northrup

No it has a sperate fuse box with 2 fuses and 2 extras. None are blowen. What should happen when I take the fuses out and have the voltage regulator hooked up?
I only know that the engine turned over, it did not run.
L M Levin

Removing the fuses will eliminate some of the factors and narrow down the focus of search.
One fuse is exclusively for the horns, and you honked it so that circuit is very likely not involved.
The other fuse protects the windshield wiper motor, "petrol warning light," & brake lights. The fact that you may have 35 Amp fuses raises the possibility that the "30 Amp" draw might just be low enough not to blow the fuse, but I think the fuse would blow. If you have the drain with the fuse in, but it disappears with the fuse out, we'll know where to go from there.
It looks like the ignition, fuel pump and headlights are not on fused circuits, but the headlight came on with normal amperage and the ignition & fuel pump ran the engine, so these are not highly suspect. Disconnecting the wires on fuse block A3 terminal would tell for sure.
What's suspicious... maybe the regulator could be the culprit, ...the generator field partially shorting to ground, say, due to poor wire insulation, or broken insulator or something touching the terminal (disconnecting the field wire at the regulator would tell if that flow was going through the field circuit)...
the fact that your "ignition warning lamp" does not come on raises a flag, THE WIRE FROM REGULATOR TERMINAL "D" TO THE WARNING LIGHT MIGHT BE SHORTING; SEE IF IT IS DISCONNECTED FROM THE SOCKET OR PINCHED IN THE FIREWALL HOLE....

I figured your engine didn't really run, but turned over. If it had actually run, someone would've had to do some serious rewiring.
Here it is 3:15 AM again. Gotta quit.
jrn Northrup

One fuse (50 amp) serves the horns only, directly from the battery and will not register on the ammeter. The 35 amp fuse, fed from the battery (Brown wire), via the ammeter (Brown/White wire), terminal A, through the series coil in the original regulator to A1, to the ignition switch Terminal A (Brown/Blue wire) out on Terminal IG (White) which also feeds the coil and fuel pump (unfused), through the fuse and feeds (Green wire)the wiper motor, fuel warning light, brake lights and turn signals. All of these circuits will register on the ammeter, so it is possible for the ammeter to read in excess of 30 amps without blowing the fuse if the line to the coil or the fuel pump were shorted to ground (although there would probably be lots of smoke from the white wire were that to happen). Remember that the ammeter in the TD is a rather primitive instrument, consisting of a single loop of wire that is about a AWG 12 or 10 equivalent in size and a magnetized vane attached to the needle. I don't give a lot of weight to the absolute value of the reading on it, rather looking at is as a relative indication of the current being drawn.

The fuses are meant to be the British style fuses with a dual rating, i.e. 17/35 amp. Meaning that the fuse will not blow at 17 amps and will blow progressively quicker as the current increases toward 35 amps at which point it will blow nearly instantaneously at 35 amps. I don't recall what the lower rating is on the 50 amp fuse is, but it is probably somewhere around 25 amps. Standard American 3AG glass fuses have similar ratings, but are marked only by the lower rating, which will blow after 4 hours at 100% of the rated value and will blow in 5 to 20 seconds at 200% of rated value. Cheers - Dave
David DuBois

And now the rest of the story. I sent the regulator back to Bob Jeffers at Milton Auto Electric to check it out and here is what he found. 2 blown intergated circuts. He is repairing and shipping back today. As soon as I receive the regulator I will install and see what happens. I will up date you all as soon as I have news. Thanks for helping me out.
L M Levin

This thread was discussed between 25/09/2009 and 01/10/2009

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