C4- What is a good average volt reading when at idle? I have gone thru 4 alternators so far. Just put a new one in a couple of days ago. I was told that sometimes the alternators are just no good from the beginning??? On the last altenator, while cruising down the highway, my volts dropped down & Killed the motor. Now that I have another alt. I was wondering about an average I should expect the reading to be? If this one goes it will most likely be a grounding issue.

 

It seems on mine that the longer it idles the lower the reading. That's mostly true in hot outside temps.

 

all three of my c-4 corvettes stay in the 13.5-14 volt range at idle if that helps

 

Hi,

I've seen a lot of alt failures in the 91 -85 Vettes. Some say it is caused by having a low state of charge in the battery due to long storage times with no trickle charging. The alternator is not really designed to recharge a very low battery. Because so many of us do let the Vette sit in the garage, the alternator tries to recharge the battery and heats up which seems to cause the failures. There are replacement alternators that can put out more "juice" and not heat up as bad. See http://www.corvetteclinicinc.com and look under C-4 solutions for alternator upgrades. Hope this helps

:flag :flag :flag

 

Mine seems to sit on 13.8 a lot of the time.

 

It needs to be over 13.5V.

Mine is dying on me right now, it fluctuates wildly from 12.6-14.1V at idle. I'm going to replace it with the CS144 alternator soon.

 

When you have the trickle charger on should you disconnect the battery or is it OK to leave it hooked up?

Sorry if this is a stupid question :crazy:

Also.....is something wrong with my Vette?...I have never owned a car that didn't buzz at you if you left the lights on....mine is silent when I leave the lights on (like I did last night while I was at the movies :smash: )

 

I was watching mine yesterday. It fluctuates between 13.5 - 13.8

 

Wow this forum is impressive, so many to help & in no time at all. Thanks guys for all the advise. Clarify this for me. When I asked for idle volts, What I meant was at the inital startup, before you touch the gas. Is mine low? at start up it only registers 11.4.

 

12.6 - 14,1 at idle, but it depends on how many acessories is on/off (lights, rear window defroster, air etc)

 

My 94 with auto reads 13.5-14.8. varies with engine speed.

 

Mine reads like 9.5-10.5 V when i first turn the ignition in the morning. This tells me that the battery is being drained because the alternator is crap. Just after startup it jumps to like 14.1V and then stables out to the high 13s.

I just take the common sense approach, if that little red light beside the voltage reading lights up, then something is wearing down.

 

My old alternator had low output and finally died. It would drop into the 11 volt range while idling at a light. I replaced it back in Feb. or March. New one read 14+ volts just after startup but would drop to low to mid 13s after the battery was topped off from the starter drain. I replaced the main high current cable that comes from the bolt on the alternator and I used a larger size wire, a 6 gauge instead of the standard 8 gauge. I ran it from the alternator to the junction bolt that's behind the battery. You remove the side panel to get to it but you can see it if you look down behind the battery. The bolt is mounted in a plastic piece for insulation. There's about 8 wires tied to this bolt, one of them is from the battery. With this new wire my volts reads a steady 13.8 after the battery is topped off. Now I wonder how many cars have a bad high current cable or high resistance in the connectors at the ends. I also wonder if the original high current cable is what caused my old alternator to go out. Remember.... the more current you want to carry, the bigger the wire has to be to get the job done. Just food for thought.

 

My '95 ZF charges around 14.8 just after I start it, then drops back to 14.1 when all warmed up. It holds steady all the time but drops slightly at idle (13.6) if I have the lights on and foot on the brake pedal.

:cheers:

 

Yeah, batteries seem to last no more than about 1.5 years no matter how good of a bat you get. So I get the cheap ones. Well, cheapER ones. There are no cheap batteries for a Vette.

The '87 I have now has had 2 alternators and 3 batteries in 3 years. I just put the 3rd battery in and I expect to replace it in another year and a half or so.

I went out right now and after sitting all night, the voltage was 11.3V. I started it up and it immediately went to 13.9V. There might be some degradation in the wiring or conectors to the meter so whether that's a true battery reading, I don't know but I hope this helps. And I consider my charging/starting systems to be a good shape.

BIG JIM

 

My 92 usually reads between 14.8 at startup to around 13.9 to 14.1 after about 10 minutes. My 87 has a new alternator and battery and it pretty much shows a 13.8 to 14.1 all the time.

One of the Corvette mags ran an article a few years ago about C4 alternators. Part of the article dealt with upgrading the stock alternator to put out close to 125-130A. Not sure which model alternator but I think it was that used in mid to late 80's models (12SI?). The article also suggested getting the most powerful (most CCA) Group 75 battery you can find. I have seen some Group 75 batteries with upward of 910 CCA.

One of the things the article pointed out was that alternators are subject to failure through being in an excessively hot area. It said that the C4 engine compartment holds a lot of heat in and that is partly why they fail. One part of the article dealt with installing a set of fans that looked something like PC cooling fans. They mounted in the upper fenderwell (hood side) and sucked hot air out of the engine compartment and out over the top of the tire.

One of the best little battery maintainers I have found comes from Harbor Freight. I got mine on sale for $9.95. It's a "Chicago Electric Model 41288". It will provide enought current to cover the loss from the various processors that draw power with the motor off. When my 92 sits for more than about a month during the winter, I charge the battery up and attach the maintainer and just leave it. I don't disconnect the battery so if I want to drive the car, I just pull the leads and off I go.

 

[QUOTE]Mine reads like 9.5-10.5 V when i first turn the ignition in the morning. This tells me that the battery is being drained because the alternator is crap. Just after startup it jumps to like 14.1V and then stables out to the high 13s.

QUOTE]

Actually that is telling me that you have a slow drain somewhere in your electrical system that is draining your battery overnight. If your alt is putting out 14v when running there isn't anything wrong with the alt. When your running voltage goes under 12.6v that means that your battery is in a drain mode.

 

Mine's about 12.8 at idle.

 

My first sign of probs with the battery is if I do a little interior work and leave the doors open even for a short time, it won't start. If it gets really bad, I come out in the morning and it won't start. Then I change the battery and it's OK for another year and a half or so.

I also has a door switch staying on and not shutting the interior lights off. I didn't notice it right away because the interior lights stay on for a few minutes anyway when everything is working right and by the time they should have shut off, I was in the house already.

BG JIM

 

Mine runs from about 13.8-14.4.