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Old 05-02-2004, 11:52 PM   #1
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Default help! Electrical gremlins eating my lunch

Been reading the forums for about a month now, some good stuff here. But now I'm in need of some serious help. I've got a 94 SE non-super charged with what looks to be an alternator/voltage problem. The alternator is a stock 105 amp. The problem I'm seeing is that when I start up the car when the engine is cold, the battery gauge shows a slight overcharge (maybe about 15v if going by the gauge). As the car warms up, the voltage drops to below 14v. When I stop the car, say at traffic light, I can see the votage drop some more, and then my oil gauge will begin to quiver. The needle on the battery gauge may quiver as well, but not necessarily in concert with the oil gauge. If I turn on other elctrical devices, like the heater blower, or the rear defroster, I can watch the needle on the battery gauge go down slightly with each device that gets turned on to the point where the needle is almost to the tick mark between 8 & 14 on the gauge (11V?). Other things I've notice from time to time is the fuel gauge suddenly dipping to near empty them coming back, the "inflatable restraint" light flashing, lights dimming at night, and the traction control coming on when I backup. These last few things have only happend a few times, the stuff with the gauges happens all the time. Heres'* what i've done so far:

1. replaced the alternator, previous owner said this happened before, alternator fixed it. I got a delco rebuilt from car quest, and I swapped batteries with my 95 bonny that'* been running fine. The 95 still runs fine, the 94 has the same problem.

2. disconnect the grounds from the engine block & fender, cleaned all contact points with emory cloth & re-attached. Did the same for the positive cables from the alternator up to the Maxifuse block. Checked and cleaned all contact points at the battery as well.

3. check for voltage drops across all cables to/from battery while engine running with as many loads on as possible (except starter cable, no problems with starter(yet)). Would only see .1 to .2 volts drop across any one cable

4. removed and checked plug-in cable from alternator all the way back to the PCM. No shorts, opens or high resistance. Check for voltage on pin L of this connector, seeing
10.5 to 10.6 when disconnected from alternator and engine running. Same as my 95 when I check it like this.

5. Swapped PCM'* with my 95 bonny (retained same PROM for each car, figured PROMs would be different for 3.8 Series I and II engines)

I've been checking alot of this against my other 2 bonnys, but those are 95'* and they have the 140 amp alternators on them. Been reading the shop manuals and using AllDate online. I've seen a very similar posting by Bonny95 and jkinney, but have not been able to get a reply from them through PM. Looking for new ideas please!
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Old 05-03-2004, 01:57 AM   #2
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If it'* just a voltage drop, it'* fairly normal. We have pretty weak stock electrical systems.

I noticed you changed the Alt. Did you change the battery with it? If having alternator problems, it could have whacked your battery too. I upped my battery to (I think) an 800 cca, and it helped some with mine. If I run across them oney, I'm upping my Alt to a 200 amp from Domestic Performance
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Old 05-03-2004, 10:16 AM   #3
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yeah, I swapped the battery with one of my 95 bonny'* that was running fine. The 95 shows no ill effects, so I think tha battery was ok.

I can understand a little voltage drop, but when it seems to affect other things, that gets me worried. And why does the voltage drop just after warming the engine? Would a larger alt help? I'm not even sure if there is one for the 94'* (at least GM doesn't list one). Tried to take the 140 amp alt from a 95 and try it on the 94, but there'* a 3rd mounting point on the 95'* alt that won't let me mount it up.

Any other idea'*? I need something to do next weekend...........!
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Old 05-03-2004, 11:04 AM   #4
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that is because the 95 is a Series II and your 94 is a Series I
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Old 05-03-2004, 11:19 AM   #5
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Did you check fuses? I have heard of wierd problems caused by blown fuses. Also, maybe try pulling fuses to see if something is shorting out and pulling too much power.
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Old 05-03-2004, 02:03 PM   #6
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Quote:
Originally Posted by wam319
I can understand a little voltage drop, but when it seems to affect other things, that gets me worried. And why does the voltage drop just after warming the engine?
A hot engine heats up the wires, and hot wires have higher resistance than cold wires, and thus drop more voltage across them as current flows to whereever it'* going. I don't know that this phenomenon would explain the *magnitude* of your voltage difference between hot and cold, but it can take at least some of the blame.

-b
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Old 05-06-2004, 12:50 AM   #7
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I'm still here, and check in from time to time to see if anyone else had encountered this prob. I did finally PM you back, which I'm sure you've seen by now. I took my entire dash out and cleaned all connectors, and in the process of re-assembling this weekend. I think I agree with enmityst on the heat theory. I noticed a huge increase when I pulled the fuses from the Maxifuse center and cleaned both the prongs, and sockets. The fuses showed alot of discoloration due to heat, which led me to completely disassemble the dash and get the main connectors that feed the instrument panel. The circuits I tracked down that feed back to the PCM from the Maxifuse center, go through this connector and I just wanted to visually check the wiring as well. The wire that feeds back to the alternator loops via the Maxifuse center through to the PCM, which signals the alternator for voltage output. Hopefully, I will be able to report some good news after this weekend. I did invest in some contact cleaner, and a tube of thermal grease. I took advantage of having the dash out, and ordered (GMPARTSDIRECT) a new lower steering column bearing (previous owner stripped thread on housing) and replaced the door actuator for the climate control (stripped gear). Can you tell I really love this car?
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Old 05-11-2004, 02:24 PM   #8
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Response to WAM319

I have the very same car.Cleaned up all possible grounds & connections.
The charging system is doing much better.
Now when I drive the car at highway speed for a while and then park it
the battery will overheat and start leaking acid from the seal around the cover.
My alternator is a Bosch 105 amp.


Reggie
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Old 05-11-2004, 04:28 PM   #9
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Sounds like the alternators internal voltage regulator (actually called something else) is cooking it.
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Old 05-16-2004, 02:08 PM   #10
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wam319
Quote:
Tried to take the 140 amp alt from a 95 and try it on the 94, but there'* a 3rd mounting point on the 95'* alt that won't let me mount it up.
Upgrading from 105A to 140A shouldn't make any difference with reference to the symptoms you describe. Those specs are just the full load output ratings of the generators. The charging current that they supply to the cars battery should never approach those high currents. It would be interesting though if you could get a DC clamp on ammeter around the output lead at the alternator terminal to check charging current especially after engine start & additional electrical loading from accessories. There may be a prob with how the pcm interprets or monitors voltage levels in the elect. system which is contingent upon how much field is applied to generator. This is basically how the newer cars work, not sure if this applies to the 94'*, just throwing out more ideas here. The volt meter on the inst. cluster I don't think is real accurate, more just an indicator.
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