Engine/Transmission (1998.5 - 2002) Voltage

[Nate]

I was waiting at the gate for base this morning (there's usually a line of cars) and I notice that my voltage guage is reading low. Between the 8 and 14, so ~11 volts or so.



Once I got off idle and drove down the road a bit, it slowly got back up to 14v, where it is normally.



I have my 18' car hauler with me, so I'm not sure if it's something with that?? Would it make sense that the trailer would pull that much power?



I came back from camping last night, about 300 mile drive and I could smell a faint plastic burning in the cab. I ended up loosing trailer lights (plug is loose or something), but I was under the hood checking the fuses and could smell it, but couldn't tell from where.



Also. .

The past few weeks when I fire up the truck in the AM, it's been cranking a bit slower. It could be just the colder weather... or low voltage? Batteries are only a few years old.



Any ideas?

 

[mhenon]

Do you have a hot line somewhere that's not fused? If it had a fuse it would have blew and not melted the line.

Mike

 

[isb360]

will the gauge spring back to where it should be when the trailer electrical hook-up is disconnected?

 

[Nate]

Still doing it without the trailer.



Voltage reads around 10 volts and almost hits 14v after a while of driving... . like there's a big electrical load.



I'm gonna test the batteries though they are fairly new.

 

[Nate]

I got it checked at Napa. Both batterries were good according to the guy... but I believe they need to be disco'd from each other to test that?



The alternator isn't charging 100% though. It's not "bad" but was reading "low" on the meter.



Not sure if the alternator is crapping out, or maybe I have a bad battery cable or something. I'm going to pull the alternator off and bench test it sometime next week to see what's going on.

 

[Nate]

Does this sound like worn brushes in the alternator???





It is charging at ~12. 23v. As far as I know, ~13. 8 is where it should be charging.



I'd hate to spend $200 on a new alternator when all I need is a set of $30 brushes from Larry B.

 

[CHill]

I had this same problem when hooked to my 5th wheel camper. I started to smell electrical burning and the voltage started dropping. It was the brake light switch module shorting out. Replaced the unit which took about 5 minutes and problem solved.

 

[PC12Driver]

I got it checked at Napa. Both batterries were good according to the guy... but I believe they need to be disco'd from each other to test that?

Absolutely. The only way to load test the batteries is to separate them from each other. All you need to do is pull the ground on one of them, and then put the tester on each one separately. If they weren't disconnected, you're only gonna see the strongest battery in the system.



When one of my batteries went dead, my first indication was slower cranking. Not much slower, but noticeably slower. When I finally tested the batteries (as stated above), the driver's side showed 12-ish volts until I hit it with the load, then it went down to 2v and didn't come back up. It was just sitting there acting like a big resistor, which will cause heat (source of hot smell?). That was a 3 year old battery. The alternator is going to try to keep that dead battery topped off, so there will be some extra heat in your charging system, too.



Bring a wrench with you back to the parts store and have them test it again with a negative pulled.



If the alternator was tested in the truck with a bad battery, that could be a reason for the low volts. 13. 8v is what to expect in a system with no load and two fully charged (good) batteries.

 

[Nate]

Ok, now it's working fine, needle is a hair about 14 volts.



I didn't do anything do it. Should I pull the alternator out and go through it still?

 

[DKnotts]

Nate, did you ever find out the real cause of the problem? Sounded to me like the alternator was going bad. Specifically one or two of the diodes of the diode trio (part of the voltage regulator section) went bad resulting in overall current output being limited. That would explain the low voltage at idle and after first starting and eventually voltage reaching the desired level of 13. 8 to 14. 4. But I don't want to speculate if you have found the solution.

 

[Nate]

Yeah I ended up replacing the alternator this weekend actually.