I have a 2002 C2 Cab, just started having the following problem. When cold voltage at the battery when running is around 13.8, as the car warms up and approaches 180 degrees the voltage falls off to around 12.33 or so. When I shut it off and start it again when hot for about 30 seconds it is back up above 13 then gradually goes back to 12.3 or so. The battery is 3.5 years old does not show bad cell on the battery charger. The battery charger when you do the alternator test shows lower than expected output. My question is should I try a new battery or is it the voltage regulator or I think I have read something about the cables from the battery to the starter and problems from the heat. Any idea?

Thanks

 

i changed my battery with a new interstate. Try changing the battery. Most battery are meant to last 3-4 years.

 

I have had this same issue on a 1999 C2. I have put on 2 different alternators, changes cables and battery. I am now of the opinion this is normal? I have never had my battery not start the car or the battery light come on. My battery charger also showed less that expecteed alternator output. Putting in a new battery did get it to were it never seems to get below 12.6 volts even when hot , ac on and cooling fans on high(I live in Florida). My voltage starts around 14 and settle in when hot at 12.5 to 13 volts.

 

I think I will try a new battery first. The indi I take the car to also suggested a battery swap.

 

Voltage regulator is the problem. It's a very easy fix, there are plenty of DIYs on it w/ PICS just print them out, and get to work, lol. Cost me a grand total of $36 to fix it.

They have more details about it, but apparently as it heats up, the regulator on that back of the alternator doesn't function properly causing a drain on your voltage. This is why it's high at startup (cool) and gets lower the longer you drive, especially in city traffic where there isn't air flow cooling things off.

Don't waste your time with the battery though, I would do this first battery second.

 

Butch199 was the voltage regulator replaced when you had the alternator done?

TSC85 I would love to take a swing at it myself but don't really have the time, I can picture my 8 year old helping out.

Thanks to all for the feedback.

 

i'm having the exact same issue. battery drains on long drives. had my porsche shop do a full diagnostic.

battery - good (only 6 months old... replaced to try and fix this problem)
starter - good
wiring - good
alternator - fine at startup, when she's warm outputs under 12.5 volts

they wanted $900 for a new alternator, one's in transit from ebay (californiastarteralternator) for a whopping $114 - new, no core charge.

have a load test done on your battery, if it checks out, buy the alternator.

my 2cents

 

yes, I put 2 rebuilt bosche alternators on that had new voltage regulators. I also replaced ground cables and new battery, voltage still goes to 12.6-13 volts when hot and ac , fans, lights all on. Seems to be normal? Never had battery too low to start

 

I took it to interstate today and when hot and under load only puts out 12.04. Where did you buy the voltage regulator from? Also where did you get the remanufactured bosche from? Thanks

 

Any special tools required to change out the alternator or can i do it with the typical stuff?

 

Igot alternator from Advance auto, paid 300 plus core, I see them on ebay for $114.
Not a hard DIY, no special tools. I got it down to less than an hr, taking my time.