Electrical Problems

[80vette_ca]

I've got some weird problems with the car that have never happened before. To start with my battery keeps going dead on me. It is a brand new battery, well actually the second new battery in about a week and a half because the first was defective. The battery dies during the day without the lights on and at night with the lights on, so I don't think they are the problem. My alternator could have been the problem because even when I put the pedal to the floor the gauge would just stay the same most of the time. Unfortunatly I just had the alternator replace and I still am getting the same problem. The guage works perfectly fine because after I charge the battery it says it is fully charged. Anybody have any ideas on what's going on. Could I be shorting something out?

 

[69_coupe]

Unfortunatly not all new alternators are functioning as they should. Try to measure the voltage at the terminal on the alternator. It should at least be 13,5 volt, if it is ok you have a problem with the connection from the alternator to the battery. If the reading is the same as the at the battery you still have a problem with your alternator.
In order to function all the wires at the alternator has to be connected. The main wire (the one connected with a nut), and one of the thin wires at the dual connector should have battery voltage all time. The other wire at the connector should have battery voltage when you turn the ignition on, this is the one connected to the charging lamp if you have one.

If the alternator is ok, you have to determine where you have your connection problem by measuring it step by step.
If I don't remember wrong, the main wire from the alternator to the battery goes from the alternator to the main connection at the starter.


Vidar

 

[theo]

Disregarding the alternator for the moment, do you have some other form of parasitic drain on the battery, causing it to go dead? It would be easiest to check this out first, before troubleshooting the alternator....
With everything off, doors closed, connect an ammeter in series with the battery. If there's more than a hundred milliamps of current (0.1A) being drawn, then this could be what's draining your battery. That's a figure off the top of my head - someone's bound to correct me - but it's a fair estimate i guess. With the ammeter still hooked up, just start pulling fuses til the current drops. Then you can isolate what circuit is draining the battery.
Apparently the interior light delay unit and the factory alarm systems are good at draining batteries, so perhaps these are your culprit.
If something's gone awry in the alternator, then if you were to disconnect all the positive leads from this ( i.e taking it "out of the loop") and you saw the current drop on the meter, then you've isolated the problem to there.

 

[69_coupe]

If I understood 80vette_ca correct the problem occured when he was driving the car. The common alternator for an 80 vette will give approx 60 Amp, so if he use less than that it should still charge the battery. But you are absolutly right about the drain from the battery if it occur when the engine is not running.
The easiest way to check it is to disconnect the negative wire from the battery, and then hook up a testlamp between the battery and the ground wire. When the lamp is lit you have solved the problem.

 

[21again]

...just start pulling fuses til the current drops. Then you can isolate what circuit is draining the battery.

I agree with this for a "down and dirty" fast isolation of the circuts past the fuse block. Just yank all the fuses and see if the problem goes away.

 

[80vette_ca]

Hey guys thanks for the help. I'll have to give them a try. I do have an electric fan that was put in last year, but I never had any problems with it draining the battery. When I notice the battery low I always turn the stereo off so I isn't that. Other that those I can't think of anything else that would drain the battery. Anybody have any idea on whether or not I could get rid of the courtesy lights without affecting any other systems because they do stay on for a long time which I've never liked.

 

[theo]

Sorry, misunderstood you! I didn't read your post properly (must learn to pay more attention!)
If the battery's dying when you're actually running, then quite simply, more amps are being drawn from it than your alternator can produce. I have a similar problem with my 80, but only when i'm using lights and defogger ie loading it highly. I'm not sure as yet whether my alt. is just underpowered for the car, or is in need of a rebuild.
Does yours have a power rating and part number stamped on its case? - for 1980, the two power ratings i know of are 61 and 70 amps.
Have you had any welding done since you put the new alt in? If you don't disconnect the alt. when welding, this can damage them...
By the way, if you want to disable the interior light delay, you need to get at the control unit. Take out the glove box interior - just half a dozen screws - and there should be a little orange box in there with a multiplug going to it, somewhere on the right pillar. Pull it out and then on the multiplug, bridge the two white wires. The interior light will now only come on with doors open, no delay.

 

[Pancho]

Hi,

I had converted our '79 to twin electric fans (because of some fan shroud issues, that's a different story). The original 63A alternator was having trouble keeping up, especially at idle on a hot day. The 'charge' light would occasionally flicker at idle.

Replacement 63A alternators were a little better, but we were still going through batteries every two years since 50% of the time (in-town driving) the system was running off the batteries, not the alternator. Tried some higher-amperage alternators which were not much better since they only crank out more power at higher RPMs.

I did some research into the charging-curve differences between the 10SI alternator used through 80-81, I think, and the 12SI used starting in 82-83. The 12SI has MUCH better capability at lower RPMs. I installed a 70A, 12SI unit (original application from a '83 5.0L Camaro, be sure and get the one with v-belt pulley, not the serpentine belt). The frame sizes of the 12SI and 10SI are the same, just be sure to get the proper pulley arrangement.

You may have to re-index the back case in order to get the plug-in connector clocked right, no big deal.

Have not had charging system problems in 2+ years. As an added benefit the 12SI has a better cooling fan/pulley arrangement, so it appears to run cooler as well.

Hope that helps,
Pancho

 

[clar2001]

Here is a shade tree menechic way to check your alt. while the car is running disconect the battery if the car dies you have a charging problem.

 

[Pancho]

I wouldn't recommend that....disconnecting the battery with the car running is also a good way to fry something......

...if the alternator IS working fine, you get a voltage spike (without the battery there to absorb some of the spikes),

....if the spike supression diodes in the alternator are bad or on their way out, you'll get an even bigger voltage spike....

...if the alternator is stuck in a 'full charge' (full-field) mode, you'll get the biggest spike of all....


Not saying I haven't done it, just that it's not a great idea !

 

[80vette_ca]

Hey guys thanks a lot I had the alternator replaced with a 70A one because the other wasn't up to par anymore. I found a short in one of the circuits which ending up being caused by the vanity mirror. A couple years ago the light wouldn't go off while storing it for the winter so the wires were just pulled apart and forgotten about. The wires were a little burnt so lets hope that and replacing the alternator while do the job.

 

[withoutremorse42]

had the same problem as the OP for the last couple of days. The culprit was the brown wire (ignition power) on the 2 wire clip going into the alternator. I rewired that to the ACC slot in the fuse box and now the alt works perfect.