Alt guage dead, slight burning smell.

[jchapin]

Hi All,

Apologize up front for long wordy post but throwing out all I currently know...

Was able to park truck at local mechanic (who has decent reputation), but otherwise disabled until we discover fix.

Symptoms: Drove 5-minutes out of driveway (~25 degrees F local temps) last night and at stop sign, detected a faint (not strong) burning smell (defroster on medium). Thought it could be coming from car in front so I pulled out and drove 1-2 miles, then "Check Gauges" idiot light illuminated with the Alt/Bat gauge dropping pretty much dead. Pulled off into parking lot, opened hood and could slightly smell the same burning scent as before. It was dark and unfortunately my toolbox with flashlight was left in garage (of course...) so I could not pinpoint where smell came from. Shut down, checked P-Codes which revealed a P-1682. Don't have device to check ECM codes (...time to purchase a scan tool). Took the walk of shame home... Came back 2hrs later, cranked over easy enough with alt/bat gauge reading 10-12, no idiot light however alt/bat gauge climbed near 14 then would drop down to 10, then climb up again, and repeat. At drop there would be brief dimming of interior lights. Decided to drive to local mechanics lot (better than a public lot) 1-2 miles towards home. While driving there I got same symptoms as original (slight burn smell, idiot light, dropped alt/bat gauge). Parked and checked under hood: no detectable smoke/smell, alternator was spinning (to rule out frozen alt pulley). While I generally plug in heater block on evenings, I always cycle grid heaters 1-2 times before cold starts.

Relevent Info: 2001 ETH/DEE, Original Alternator, 140K miles, Edge EZ, FASS 95/95, AFE, 4" full exhaust. New pair of Die Hard Platinum batteries (2 months old). Original Heater Grid Relays.

Diagnosis: My first guess is the alternator. Adding the FASS & Edge may or may not have bumped up the demands (I added them last Spring) but this Fall my 3 y/o Autozone batteries died. (forget name brand, but they were cheap replacement to get me out of a dead-battery spot (originals)). I ordered a Mean Green Alternator when replacing batteries 2-months ago, but it took them 6 weeks to deliver. So I have it and will install it today. But, I don't want to be throwing parts at it before nailing down the real problem. I am still wondering about that smell. Will bad alternators make a burning smell?? There's also possibility of an electrical short somewhere. My TDR searches revealed Heater Grid Relay problems that threw similar symptoms. I checked Heater Grid last night after a few hours shutdown and it didn't appear any warmer to touch than rest of engine. This morning I checked alt/bat gauge and it was still at about 10-11.

So that's where I'm at. Unfortunately I had to get to work, so will let the local mechanic have a look (they are not known for diesel work, but do a good job on everything else), and I gave them the new alternator to install (might as well).

Does anybody have anything else I could have checked out while in shop?

Many thanks, again sorry for long post. VR/Jack