88Woody

Had an issue this morning with my 88 Corvette. Leaving for work this morning and figured I’d take it seeing as there wouldn’t be too many cars on the road. Didn’t exactly start right away but I figured it was cold as it sits out overnight under a cover. Anyway, I let het warm up and left for work. About 15 minutes into the trip the radio starts crackling (I had the heat on, headlights on, and radio) and suddenly all the displays go dim and fan for the heater stops. Car’s still running so I turn around to head home. After a few minutes the car’s bucking and then turns off. My wife came and broke jumper cables. Car starts right up, so I quickly try to get it back home. Dies again. Jumped it again and let it run a bit more. This time she stayed running so I could get it home. I didn’t put anything electrical on and for the 10 minutes it took to get home she seemed fine.
The battery isn’t new, so I’m kind of thinking this is the issue. But I figured seeing as I don’t know too much about these cars (yet) I’d ask if anyone has had a similar problem. The alternator is new, and the wires/connections seem fine.

So …. Battery or something else? Btw, temp outside was a balmy 23 degrees.

Thanks all and Happy New Year!

bassackwards

You are not getting a charge. What voltage on the gauge when it is running?

My 92 did this and I found an unplugged wire on the backside of the alternator. Plugged it in and had been fine since.

AirForceOne!

Definately check the battery terminals first! Undo them and clean them good and try that.

c4cruiser

What was the voltage reading?? Assuming the battery is good and the alternator can produce the required volts and amperage, look for something like 14.2 to 14.5 volts or so when the engine is cold and is started. With just the ignition on and nothing is use, look for 11.8 to 12.3 volts or so. These are just ranges and you could see .1 to .3 more or less.

Once the alternator provides enough current to the battery, you should see something like 13.4 to 13.9 or so. Add headlights, radio, heater fan and such, you should see 13.8 to 14.1 or so.

This assumes a battery in good condition. I would have the battery load tested and the alternator tested. And IMHO, don't take the car to a chain parts store. The type of testing the do is primitive compared to a reputable auto repair shop. IF you do need a battery, get a good one. Our shop recommends both Interstate batteries and AC Delco "Professional" series batteries.

88Woody

Excellent, people. Thank you for the quick responses. I didn't have a chance to check the voltage because I had to run back out to work and I was late as it was. I'll definitely check these out tonight.

c4cruiser

Set the dash switch to display volts and then you can keep an eye on what's going on. Look for gradual drops or spikes in the voltage as you drive.

If you have a digital volt meter, you can easily check the voltage at the battery (engine off) then with the engine idling, check the voltage at the alternator and at the battery.

383vett

Check terminals.

88Woody

Ok, just started the car which started right up after sitting since 8:00 this morning. Voltage is reading 11.4 with engine just started. Battery light (idiot light) is on. Never was on before.
With lights, radio, and heat on voltage is at 10.9 volts. This battery is far from new. Voltage keeps dropping now. After 2 minutes down to 10.4. Turned all off and voltage went back up to 11.0

88Woody

And just put all back on. Voltage dropping to 8.8. Dash very dim now like it was. Everything off, voltage back up to only 9.8

Red89'-L98

Had this problem a month ago and it was the red wire on the back of the alternator was corroded where it made contact with the alternator and half the wires were broken and the connector was burnt looking badly.

I chopped off part of the wire (the inch that was bad until it go to a better part of the wire) and bought some of the connectors and fixed it and it has been perfectly fine ever since.

In a few days I will be completely replacing that wire with a newer and better one to prevent future issues from it for a long while. I probably don't have to but I am just in case.

Hope this helps, Stephen

c4cruiser

Sounds like it's time for a new battery. A battery is discharged when it shows a voltage of 12v or less. Your battery could have a dead cell or internal short.

Get a new one installed and then check the alternator output using a digital voltmeter at the large red wire with the engine running. If the alternator is good, you should see much higher voltages and are consistent.

theadmiral94

It could be the battery being so bad the alternator can't get it up to power.

or more likely, based on the decreasing voltage, it could be the alternator or the wires to the alternator (as others have suggested).

To prove/disprove it being a battery, suggest disconnecting the battery negative terminal, put on dummy post, charge the battery, wait 24 hours, then test the battery's voltage with a good digital VOM. voltage should read at/near 100% (see table below). If lower than 50%, get a new battery.

12.66vDC = 100%, 12.4 = 75%, 12.2 = 50%, 12.0 = 25%.

Cliff Harris

Your alternator is definitely not charging the battery (or running the car). Could be a bad alternator or bad wiring between alternator and battery.

Also there is a connection to the alternator from the ignition switch that enables the regulator inside the alternator. If there is a problem with that wire (or connection) then the alternator will not "turn on".

88Woody

Ok, bought a new battery and voltage is reading a constant 11.0 with everything on. Coolant temp is at 181. Battery light still on though. The voltage is reading less than what you guys are saying though, which concerns me. Been running for about 20 minutes with no change is voltage either up or down. Should the battery light still be on? Does it need to reset itself? Everything off and it reads 11.4 volts.

88Woody

Temp reading now at 221 with voltage the same at 11 4

theadmiral94

Darn, then the battery was not the primary problem.

Voltage with engine running and alternator working should be 13+ volts.

The problem is with the alternator (most likely the regulator therein) and/or its output wire and/or the sensing wire.

Suggest removing the alternator wires and inspect and check for the voltage compared directly to the battery. given the gauge of the wire, there should be NO voltage drop, so any might indicate a partially broken wire or end-connector.

IF no wire problems found, then remove alternator and have it tested.

88Woody

Yeah, I'm leaning towards that as well but I don't have a volt meter. Only the one on the dash. The voltage holds steady even with everything electrical going. So the battery is getting some charge just not what it should be. I'll bring it in and hope its only a bad wire or terminal lead to the battery. Better than it was but definitely not where it should be.

Anyway thanks for the input

Red89'-L98

I would do like he said and check for any broken or damaged wires, particularly the ends of them for any corrosion or broken wires.

You can read an earlier post I made on this thread and see in a little more detain what I am talking about.

Also check the rings terminal that the wire goes in and make sure it is getting a secure connection and it not damaged.

theadmiral94

Your welcome.

BTW, running the car at 11vDC will quickly destroy your new battery (note my earlier post -- 12 vDC implies a near dead battery). So, be VERY careful driving the car as is -- and DO NOT turn on any electrical devices (including the heat & radio) until repaired. Low voltage will damage electrical motors (coolant fans, heater fan, seat motors, antenna motor) and may damage electronics (e.g. dash, CCM, alarm, ECM).

FYI, Volt meters (aka VOM) are inexpensive ($20-$50, better ones have 'high impedence' to reduce damage chances to sensitive electronics), they are very easy to use, and a great way to diagnose simple problems and save lots of dough -- no garage should be without one -- next time your at Wally, Radio Shack or a car parts place, pick up a Fluke or similiar brand, worth their weight in gold...

c4cruiser

It's time to remove the alternator and take it to some place where it can be tested. Most of the chain parts stores like AutoZone will have a way to test alternator output.

Your voltage readings are certainly not right. I'll bet the battery voltage if tested now will be somewhere around 12.3 to 12.0v; that would be an indication of a discharged battery. If the alternator is not providing sufficient current to keep the battery is a charged state, that's why you see the low voltage being displayed.