The battery in my '88 convertible drains after setting for one week. I hooked up a test light on the negative side of the battery and went through all the fuses in the driver's side kick panel and none of then made a difference in the brightness of my test light. I then pulled the fuses in the engine bay. The only way I could change the brightness was when I took out the main 80 amp fuse and then the light went out completely. Any ideas on this?

Thank you,

 

How much of a drain, enough so the car won't start?

Obviously the factory alarm and radio use some power.

I let my '88 vert sit for 2 or 3 weeks in the winter so I use a quick disconnect on the battery.

 

It may just be a bad battery, plain and simple. How old is it? If its more than 4-5 years old it wouldn't hurt to get a new one anyway, before you get stuck somewhere because of it.

 

The battery in the car is new. When I say the battery drains, I mean it is completely dead after one week.
When I bought the car it was doing this and the previous owner said it had a weak battery. I went and had the battery load tested and it showed "marginal" so I bought a new battery. The new battery drains just as fast as the old one.

 

dont know if this will help.

i bought a 86 rx recently and it wouldnt start because battery kept draining, make sure your alternator works for sure, the previous owner bought a new alternator and battery and it was still loosing power so i replaced all the electrical bymyself to find you the new alternator was bad... anyway never hurts to check

 

The alternator is fine, I checked that. I can charge the battery with my charger, and then just leave it in the car for a week and it is dead.

 

What I am asking for is what would be pulling current through the main 80 amp fuse, that doesn't show up when I pull out all the fuses in the kick panel and under the hood?

 

First, I would go through all the electrical systems and see if everything (windsheild washers, hazards, cruise control) all work correctly.

If they are all good, then I would set the car in a dark garage and see if there is ANY bulb glowing in the dark when they are all off.

If these both are good, then Haynes has a pretty good repair manual and it shows the paths for all the fuses.

 

My question is, if all the fuses are pulled, then how are any of the accessories going to get current?

 

Not sure if this would help, but my 88 vert had a similar problem- turned out to be a defective trunk latch, and the bulb for the trunk light was not going out after the trunk was closed.


Give that a shot- it took me a while to find!

 

On my 88 convertible when it was draining the battery, the bushings inside the alt were causing the death of my battery.

All the tests on the alt showed fine, it wasn't until they pulled it out and looked inside they saw the issue.

 

Lol, nobody ever answered your first question, so here goes-

The main fuse powers the following:
1) 30A circuit breaker for the heater & AC
2) 30A breaker for the rear defrost (prolly ain't got that)
3) the charging circuit for the alt
4) the ignition switch, and by extension, all of the "hot bus" battery powered items (the top two rows of fuses in your cabin fuse box)

First things first, disconnect the charging cable from the top of the alt, and set it off to the side (make sure it won't touch anything grounded). If the batt doesn't drain now, you have a bad alt. That was easy, eh?

If that ain't it, pull all of the top two rows of fuses from your cabin box. Insert one at a time to see if the batt drains. This might take a couple of weeks to be sure, but sooner or later you'll nail the bastard

 

Thanks WAYNE, yea right now I still have the drain eventhough every cabin fuse is pulled from the kick panel fuse box, and all the engine fuses are pulled except for the 80 amp main as per my original post. I will pull the cable off the alt and check that, one of the diodes may be bad causing it to charge normally but then allowing current to flow back through when it is parked. If it is not the alternator I will check the ignition switch circt and make sure the previous owner did not tap the line before the fuse panel.

 

Sounds like a plan, let's hope it's the alt...

 

Looks like I have a bad diode in the alternator. If I unbolt the negative terminal on the alt the drain goes away. I just ordered a fd alternator to put on the car.

 

That's a positive terminal- that's why you need to prevent it from hitting ground.

The negative terminal of the alt is actually the case...

All right, you found it with not much trouble

 

Wayne I was wondering what the heck you were talking about and then I went back and read my message. I meant to say positive, I must of had my head too far up my bosses backside at the time.

 

Well my new alternator came in and I discovered the previous owner had put a S5 alternator on the car and had just cut off the S4 plug and put a S5 plug on in its place. The only problem is that the S4 cars use a L/R setup and the S5 use a L/S setup. So the old alternator was looking for +12V at the S lead and was getting 0V from the R lead causing my battery drain through the alternator. I cut the R lead wire off and ran a +12V line from the battery to the connector making it a S lead. Anyway my new alternator is from a FD and I am good to go.

 

is ur battery brand new? and how many volt's is it pulling on ur gauge??? hope u fix ur problem best of luck josh

 

As I already stated above, the trouble is fixed. 86-88, and 89-91 alternators are not interchangable unless you modify the L/R on a S4 to the L/S config of a S5. If you do not do this your battery will drain down if your car is parked for several days.