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MG TD TF 1500 - Electrics dead?

OK, now a new problem. I changed polarity on the TD last week, and had it running just fine for hours.

Yesterday, I was tuning the carbs when suddenly the fuel pump stopped working. So did the lights and all electrics.

The starter works, and the horn blows. That's about it.

So far, the battery is fine, no fuses are blown, and I can't see any wires disconnected anywhere.

Thoughts?
Geoffrey M Baker

Did you change over the ammeter connections. If so, check they are OK. That is the only change on polarity reversal. All circuits except the horn and starter go through it,
Ray TF 2884
Ray Lee

"no fuses are blown"
Geoffrey - How did you test the fuse? If it was just by looking at it with the MK I eyeballs, you have used the absolutely worst diagnostic tool known to man for testing a fuse. You need to use a multimeter set to read ohms to read end to end of the fuse, or set it to read volts and check the voltage at each end of the fuse with the ignition turned on.

That said, the starter is not fused and the horn is on a fuse by itself. Power for everything else come from the battery to the ammeter to the A terminal of the control box out on the A1 terminal to the ignition switch, through the switch to the ignition coil and fuel pump, through the fuse to the windshield wiper, brake light switch and the fuel warning light. I would suggest checking the voltage at the A, then the A1 terminals of the control box - if there is 12 volts at those two places (with and without the ignition switch on) the next place to check is the A3 terminal of the control box or the fuse block (depending on the year of the car) - if you don't have 12 volts at that point, check your ignition switch and/or the wires going to it. Cheers - Dave
David DuBois

Ammeter. I think the grub screws are partially stripped its hard to tighten it down enough but that is definitely the problem... And yes it was properly reversed...
Geoffrey M Baker

Geoffrey - Good find. The grub screws in the ammeter are (I believe) are 2BA. If so, substitute a 10 -32 it is sufficiently larger that is should snug right up for you. Cheers - Dave
David DuBois

Another thing to check " your CLOCK " do you have the clock connected ? Take the wire from the clock , charge the battery and wait what happens . I had the same problem only to find out the clock had a internal short and drained my new Optima completely.

Cheers Gerard
Gerard Hengeveld

Sorry Gent's I is read the first post, His battery is not dead as I thought to have read.

Gerard
Gerard Hengeveld

I never bothered to change the Ammeter, it works fine both ways and I just do the conversion between my ears...

Rgds Mike
Mike Fritsch

Mike, I considered that :) But I'm a glutton for punishment.
Geoffrey M Baker

If your electrics died suddenly, that's not the battery. That's a bad connection somewhere near the battery. Probably a connection at the fuse block, ignition switch, or some similar place that will kill everything. It's very likely to be some connection that was disturbed when you did the polarity conversion.

The way to fix this is to start at the battery and trace through the system with a test light. Somewhere, you'll find voltage at one side of a connection or switch but not at the other. That's where your problem is.
S Maas

S Mass, the problem was solved; it was a wire loose at the ammeter.
Geoffrey M Baker

This thread was discussed between 20/04/2014 and 25/04/2014

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