Archived HELP, truck wants to melt...

[ASTAR]

Ok, so i just adjusted my APPS and when i started my truck to work on it before I did it had a weak battery start. I did the adjustment, left the key on for about 20 minutes and went to go test drive. It didn't start. It obviously needed new batteries so I went down to Costco, picked up a couple Optima Red Tops (yes with the spacer to make it the correct height). Well, I hook up the driver side and a minute later, I smell something getting hot under there. I found the two posts that are right behind the intake horn and one was just cooking hot. The rubber boot was melted, and it was heating up the intake horn a lot, like untouchable. I took out the two wire to inspect for damage (like grounding on something) and they are in perfect condition. They go to these things mounted on the inner driver side fenderwell (see pics). From there two wires (still connected in pictures) go to the positive terminal on the driver side battery. Any idea what these things are and why I am having this issue?

Bill from DTT is helping me (he's been awesome thanks Bill) with the APPS setting and this issue but I don't want to call him this late .

HELP!!! :{

 

[jrobinson2]

Sounds like maybe the intake grid heaters stuck on, the things circled in your pictures are the grid heater relays. I would be a little hesitant to start the engine without checking for melted debris from the heater in the intake. If there is not anything in the intake you should be able to drive it while you find the problem, it should start without the heaters at least into the high 20*s with the new batterys



Jared

 

[ASTAR]

What makes those come on in the first place?

 

[jrobinson2]

The ECM controls the relays based on temperature inputs from the coolant and air sensors, that is what's happening when the "wait to start light" is on. I doubt the problem is the controls, more likely the relay connected to the wire that got hot is probably stuck closed.



Jared

 

[ASTAR]

Well this was happening with the key "off". What would happen if I tried to run the truck without the heaters hooked up? It just seems weird that they were stuck on for no reason in the first place. Do they stay on when the truck is running the whole time if it's cold outside?

 

[jrobinson2]

After the truck is started the heaters cycle on and off for a little while, you will notice the lights dim after dark when they cycle.



What probably happened was when you tried to start the truck with the dead battery the contacts in one of the relays welded together, if the relay is stuck closed it won't matter what position the key is in.



Running without the heaters wont hurt anything as long as its warm enough outside to start without them, it will crank a bit longer and smoke a bit when its cold is all. I assume by the location under your name that it wont be cold enough to cause a problem.



As I said above my main concern would be if anything melted inside the intake and fell in the engine, that would be extremely bad if the engine was started and sucked some junk into the cylinders



Jared

 

[MMeier]

If the relay sticks " closed ", I believe the relay will still try to power up the heaters. Had a bad intake temp sensor once on my old 97 truck that would turn them on in the heat of summer, but never had an actual relay go bad, (yet) .

 

[ASTAR]

What probably happened was when you tried to start the truck with the dead battery the contacts in one of the relays welded together

Actually, that does make sense cause when I also tried to "jump" it with the wifes car and my truck was laughing at that little battery. No dice. I also noticed that the little nuts on the posts were a little loose and causing some mild arcing. I'll check the intake for any melted debris before running it and look into replacing that relay.

Thanks a ton for your help. I was stressing. :--)

 

[rkressg]

What would happen if I tried to run the truck without the heaters hooked up?

The first time I changed my Injection pump, I forgot to re-connect the grid heater. This was a total accident, and I did not realize this until winter came and I had trouble starting my truck.

I guess the wires were not close to anything and did not ground out, or else I would have had a minor weld spot somewhere.



If you are worried about it, just pull the relay. Unless it is extremely cold, your truck will almost always start.

-Rich

 

[ASTAR]

The first time I changed my Injection pump, I forgot to re-connect the grid heater. This was a total accident, and I did not realize this until winter came and I had trouble starting my truck.

I guess the wires were not close to anything and did not ground out, or else I would have had a minor weld spot somewhere.



If you are worried about it, just pull the relay. Unless it is extremely cold, your truck will almost always start.

-Rich

Yep, I left it disconnected and it's fine now. I checked the output voltage at the relay posts and sure enough, it was showing 12. 5 volts, key off. I'm just gonna replace the relay as I'm sure jrobinson is correct.