flyrade

I just want to share my experience when changing the battery on my 90 GT.

The ABS system always worked great, with no warning lights. I had Sears change my battery and as soon as I started the car I got an ABS warning light. I called my local dealer and he thought the computer in the car needed to be reset. He said they have a standard charge of $50.

When I got to the dealer I described that the only thing to cause the light was the change of battery, and after waiting in the service area for a half hour he came to tell me that resetting the computer did not fix the problem, and that now there is a problem with the right - rear anti lock brake system, and they are going to tear it apart. I told him to stop all work on the car, and I went to see the mechanic myself. I told him there is no problem with the right - rear, or any other part of the system, and that the problem has to be in the electrical system. After some checking, he found a fuse he never heard of - it was in German in his book - and sure enough when it was replaced the problem was gone.

The moral of the story is that Sears did not keep the system powered with 12 volts when they removed the battery. Then, when the new battery came on line, it blew this fuse. What they should have done is plug a small 12 volt battery into the lighter to keep the system powered, and then I would not have had this problem.

I hope this helps someone in the future during a battery change.

Pagnobito

Never heard of that, I regularly disconnect the battery on my ABS/PSD equipped 90S4 and the only thing to be wary of is the idle adaptation taking a few seconds but that is it!

I would check all the nuts are tight on the additional power cables on the positive side of the battery. (disconnect the earth first).

Or Sears didn't replace the battery correctly and caught a wire and shorted it.

123quattro

Changing the battery should not have had any affect on the ABS system.

Mrmerlin

I hope there isnt any other issues I wonder if they might have shorted some wires in the spare tire well since thats where the ABS feeds are grounded

rexpontius

Fuses should not just blow when changing the battery.

I guess that the guys who changed the battery accidentally hit / loosened / damaged the wiring of the ABS sensor which runs through the spare wheel whell (just as MrMerlin said).

I would inspect it just to make sure (the connectors are in the cylindrical shaped beige/brown units)

davek9

On the cig lighter being used to keep up 12v statement.
I thought the lighter is not powered unless the key is on, did that change on the later cars?

123quattro

Or possibly they installed the battery backwards and it popped a fuse protecting the ABS unit from reversed polarity? Then they put it in the right way and didn't mention it.

SeanR

Putting 12v power to the cig lighter is not going to do anything but waste someones time. These things happen on 20 year old cars.

Alan

NO it didn't change - so it won't work.

Just like how charging via the outlet won't work either. A few folks have said their's are always powered - but it was never supposed to be configured this way (so likely changed by a PO).

It is likely that a charger connected this way will look like its charging - since it will be powering everything that sits on the accessory line.

There shoud be no need to maintain power for the ABS - there is however some advantage to keeping power to the LH. Not that it impacts functional operation - only that it will have to do readaptation otherwise.

Something else happened here... In general there is no real risk in disconnecting/replacing the battery (except if you manage to reverse it - rather hard to do with a stock battery). Charging the battery while connected to the vehicle with a poor quality high current charger is a much bigger risk (always disconnect the battery for med/fast rate charging).

Alan

SeanR

The only 928's I've encountered where the cig lighter is always powered have been '88's. All of them, very odd also.

mdkelly1

Mine is an '88 and the lighter is always powered as well.