First post here!! Unfortunately, already need help diagnosing an electrical issue with my daily driver. Two weeks ago, left for work, about 1/4 mile into the commute I received warning tones and warning light "check gauges". Noticed that my voltage was zero. Could not stop as I was running a little late to work, hoped for the best, and continued on for the next three miles with no difficulties (except for gauge continuing at zero). Prior to this, truck was plugged in but ambient temp was still below zero F at time of commute. Got to work without event, turned off truck and immediately restarted it to see gauge move up to 10 and pulsate from 10 to 8 with each firing of heating grid. Took truck to mechanic next day (voltage came back up to 14). He told me that batteries were surprisingly good considering their age (orignal batteries), computer was signaling alternator to work, and he suggested replacing alternator anyway. I went to NAPA and bought two new batteries and new alternator and put them on truck. So far so good...

Three hours ago, I was traveling to different station so I started up the truck and about 5 minutes into commute I received warning tones, check gauges light, and zero reading on alternator. Truck is very cold as wind chill is close to 10 above right now. I turn off truck at traffic light and immediately restart it to see volts recover to 10 and a few minutes later drop back to zero and receive same warnings. Get to destination and truck is now warm, volts show 14. I performed key procedure to get p1682 code. Spend a few hours at station, get relieved to head back to normal assignment and volts never drop below 14 (truck is still warm).

I know that the alternator is controlled by the voltage regulator in the PCM. If my mechanic said that the computer is telling the alternator to work does that mean that the voltage regulator is working regardless of temperature? Is there something wrong with my heating grid making them stay on too long causing my voltage to plummet? Bad heating grid relays????

Thank you!!

 

i have a similar issue right now. once in a blue moon over the last year and a half this happens to me - but i notice nothing symptom-wise (besides idiot light and voltage gauge).
i had my alternator tested and it is shot - maybe that is my problem.
also, this usually happened when the truck was really cold.
i don't remember my p-code though

 

Have you found a remedy? I have replaced the alternator and batteries 5 days ago and still have problems with low voltage warning when truck is cold.

 

Just walked out to my truck to notice smoke coming from the grill. Popped open the hood and noticed the gasket between the intake and the heat grid boiling, the wires connecting the heat grid melted, and the intake plenum now discolored!! I snuffed out the fire, disconnected the batteries and now await some advice on what to do next...

 

You have a sticking heater relay.

 

Should I also replace the grid heater?