Electrical short?

[86in]

Hello fellow olds owners. I have an 86 Cutlass Supreme V8 with a new batt and alt., but the batt. still goes dead in about a half hour or so. I was told I might have a short somewhere, any help would be greatly appreciated.

[texasred]

30 minutes? Seems like a pretty serious drain.

Got a multimeter? Remove the negative battery cable and then pull out all the fuses. Connect the voltmeter between the negative terminal and the negative cable. Should read zero (nothing running, no drain). Put the fuses back in one at a time, but leave the clock for last (it has a constant draw) and radio (probably a draw to hold the memory). The fuse that causes a draw will be the circuit that's the culprit. You should be able to shoot it down from there.

My best guess would be the ignition circuit...but that is ONLY a guess.

Good luck!

C.J.

[86in]

well, in about a half hour you start to notice, dimming lights, feels like its gonna stall, radio goes off. After i pull the fuses, then what? I really appriciate the help.

[texasred]

Now understand, I'm not familiar with the wiring on them "newfangled" cars (I run a 71 Cutlass).

Like I said, with the voltmeter between the neg battery terminal and the neg wire (which you removed) when you plug in the fuse with the "powered" circuit, you will see the voltmeter read 12 volts. The only circuits you should normally get a reading on are the radio and clock. Oh, and lights if you have the door open or an underhood light.

You can also try oldspower.com and realoldspower.com. Lots of folks there run your vintage car and they are both quite lively boards. They could probably give you better specifics for the 86's.

C.J.

[Oldsguy]

You should be able to pull a code, or have a parts store check your alternator while in the car. I bet your alternator isn't charging, that would probably mean faulty wiring. By new batt and alt do you mean new from the store or new to you? Also, was the batt fully charged when installed? Lots of variables involved here but I bet is is something simple

[86in]

well, with my test light between the neg. terminal and neg. cable, i pulled fuses until the light went out. The light went out when i pulled the fuse for the dome light. NOW WHAT? I am no mechanic whatsoever, so please excuse my lack of knowledge.

[texasred]

You know the clock pulls power all the time. You know the dome light has power with the door open. Set those two aside for now.

Put the other fuses in one at a time. Check your test light after installing each one. Remove the fuse again before going to the next. Make note of the ones that light the light.

Which ones made it light?

C.J.

[ January 12, 2005: Message edited by: texasred ]</p>

[86in]

I pulled every fuse that i can see, it went out when i pulled the fuse labeled dome. A couple people seem to think my starter might be draining the batt. What i dont understand is if the car is running off the alternator when it is running, why would the car eventually stall? The new battery is being fully charged now, how do i see if the starter is the culprit? I greatly app. all your help. My wife does not like my car at all, she says we are " a special group of people." I knew i could find help here!

[86in]

i have a haynes repair manual for the car and it has the wiring schematics for the dome fuse. It seems to be tied in with all othet interior lights. I suppose just pulling that fuse wont work? I tried that and it still went dead in about 20 min on an already somewhat drained batt.

[Oldsguy]

have your alternator checked to see if it is really charging. Your car doesn't run off the alternator, it runs off the battery which is a voltage storage device, your alternator re-charges the battery at a rate which is supposed to be faster than what the car can discharge the battery UNDER NORMAL CIRCUMSTANCES. If you have faulty wiring or a faulty alternator then it will not work as it was designed to. Pulling the interior lights fuse only proves that the dome light is not the problem. Besides, as texasred said the dome light will be on when the door is open and you probably had the door open when you did the test of pulling the fuse out while monitoring your test lite between the neg battery cable and the negative battery post. If your alternator tests good in the car then your friends might be right about the starter but that would be a problem with your ignition switch/circuit because it is supposed to turn the ignition circuit off when the key is out. Your starter is part of that circuit and it would be possible to drain your battery that way. Finally, is your battery new? Have you fully charged it on a slow charger over night? You might have a bad battery. In retrospect, you should check that first, then the alternator, then the ignition circuit.

[86in]

Well, i just read on another site that someone had the same problem. A new alt and batt. and belt but still no charge. His power steering belt was slipping and he put some type of grip stuff on there and the charge instantly when up to 13 or 14 volts. ALSO, I had mt alt. tested in the car while running at autozone, they said it was charging, but they had me rev it up and keep it at about 2000 rpm's. Another place checked it at idle and said no charge. is it possible that it showed a charge at autozone cause they me keep the rpms up?

[86in]

just had the alt. tested and no charge while running at idle. He said check the wires on the starter for damage. Gonna do that

[Oldsguy]

It appears that you may be on the right track. An alternator will charge better at a higher rpm than it does at idle, but then, that depends on how low your idle is set and the alternator itself as well..
good luck.

[DougFL]

Sorry to bud in - but I have a very similiar issue here, however I am 100% positive that the Alternator is putting out 14+ volts all the time. However, after 1 or 2 drives of a few miles, I can not start the engine and see that the battery has dropped most of it's charge.

When I have a fully charged battery and attach a voltmeter I read fine (around 12.5). When I turn on the accessories I get a slight drain but returns normal when I turn them off. I have tried everything (checking shorts for fuses etc), and can't seem to pinpoint anything.

My question is let's say the alternator is working correctly (14+ volts), when the car is on and driving, can it pull more than this? A car usually pulls on 12v during normal operating conditions correct?

[ January 22, 2005: Message edited by: DougFL ]</p>

[Oldsguy]

A healthy battery should read 13.4 to 13.8 volts no-load easy. You might take a closer look at your battery.

[86in]

Well, I have finally figured it out!!! The "hot" wire from the back of the alt. to the batt. was bad. I had the alt. tested again out of the car and it was good, but in the car is wasnt doing its job. So I figured it was that wire. And thank god it was. FINALLY. Dougfl, my little bit of experience would say make sure when you recharge the batt., that it gets fully charged, and normal operating range is like 13 something to 14.5. The battery is 12 so the alt. replenishes it faster than it can drain. Sounds like the alt. is struggling to charge the batt as it is running. What kind and year car is it? Good luck, I ll keep checking in to see how it is going.

[86in]

Oldsguy and texasred, thanks for all the help.

[Oldsguy]

No problem, that's one of the reasons for a forum like this. Sorry I didn't think of that one earlier to save you some time though..

[DougFL]

hey guys thanks for the help...

my electrical setup is using an internally regulated alternator.

is this situation normal?
car is off. take battery - undo both cables. use voltmeter between battery and negative cable (like examples above). and connect wire from positive termal to the #2 (voltage-sensing) terminal on alternator. My voltmeter jumps to around 12.5 (charge of battery). Does this mean the alternator is drawing 12.5 volts from the battery even when not running?

Thanks again,
Doug

[Oldsguy]

Doug, it sounds to me like you have your voltmeter set up to measure current, not voltage. Measuring in series between the negative cable and the battery (I hope you mean the negative terminal on the battery) will be a setup for current only, you should read no votage at all. Are you sure you didn't have the setting on the voltmeter on current? Usually indicated by a straight dash for dc current or a curved dash for ac current. The test light is a current indicating device which by ohms law means that there must be a voltage difference of potential between the two points being measured if the lamp is illuminated. The way you described your set-up, if you checked for current and had a positive indication then that would be an abnormal result. Under normal conditions your alternator should not draw current (drain voltage) from the battery when the engine is not running.