Engine/Transmission (1998.5 - 2002) Alternator quits charging after 10 min. of driving.

[tmacc]

The alternator will charge for about 5-10 minutes after starting and then it completely quits. I took it by NAPA and they put a gauge on it and said the alternator was bad. I put on a new one and the same thing happened. Fortunately, they will let me return the new alternator. Since the regulator is in the ECM, do I have to replace that? I got a code P1693 "A fault has been generated in the companion engine control module" and P1682 "Charging system output too low" (Well, Duh!) when I turned the key 3X. Looking for suggestions on where to go from here.
Thanks in advance
Tom

 

[JR]

If they let you return the new altenator, does that mean the old one was fine?
Battery cables and connections connections clean and tight?
Batteries charged and load tested?
How about grounds? (clean and tight)
Condition of 140 amp fusible link in the PDC under the hood?
Do you have a functional tach?

 

[tmacc]

If they let you return the new alternator, does that mean the old one was fine? .........Sorry if I wasn't clear. Yes, I assume that if the new alternator was exhibiting the symptoms as the old one, the old one was good. It was only a year or so old anyway.

Battery cables and connections connections clean and tight? .........They are tight and fairly clean. No major build up of crap.

Batteries charged and load tested? .........Haven't checked them but they were new last year.

How about grounds? (clean and tight) ........At the battery? They're good.

Condition of 140 amp fusible link in the PDC under the hood? ......I'll check it tomorrow. Would the truck even start if it was blown?

Do you have a functional tach? ........Yup.

Really, everything runs great for a truck with 282K miles on it.....except the charging circuit.

JR. Thanks for the suggestions of items to check. I'll check tomorrow.

 

[JR]

Don't forget to check both ends of the ground cables. Even though your batteries are new you may consider having them load tested. Stranger things have happened. They do fail. I bought a new battery for my wifes VW TDI last year and installed it to find out it had a dead short in it.
If you have a voltmeter, take a quick reading of the batteries after they've been sitting for a while, and immediately after you start the truck and monitor for a few minutes after to see if they are recovering or not. May give you an idea on which direction to go

 

[Bill Lins]

Not sure about your's but my '98 has a heat sensor under the driver's side battery that's supposed to signal the voltage regulator how much charging current to send. If you have the same thing, it may be acting up. Just one more thing to check- good luck with it.

 

[klcammie]

Not sure about your's but my '98 has a heat sensor under the driver's side battery that's supposed to signal the voltage regulator how much charging current to send. If you have the same thing, it may be acting up. Just one more thing to check- good luck with it.

My 01 has the sensor under the batt. I agree check it.