can't shut engine off...whats next!

[banditt11]

I can't win for losing I guess. I wrote earlier about my computer going nuts in the cold weather. Now when I am done at the end of the day my truck will not shut off when I turn off the key. The warning lights come on and buzz and the parking brake light comes on and flickers. I have to wait for the opti idle to shut it off and even then there is still power going to the fan and gages. The truck starts fine even though there is a delay of the warning lights and buzzers going off. everything is fine after that. End of the day I go thru the same routine. Batteries are just fine also. This one has me buffaloed for sure. Oh I actually unhooked the batteries and then rehooked thinking maybe the computer would reset? But no change in the way it acts.

Frank

[bibnflannel]

Dont know if this would help or not, but I was listening to sirius radios trucking channel yesterday and they had the maintenance foreman for Prime on the air answering questions. A guy called in and he was having similar problems with his computer, allthough I dont recall exactly was his situation was. The Prime guy told him to unplug the main wiring harnesses on each side of his computer module {down next to the mainframe on the side the engine block}, spray some lubricant on the terminal plugs, perhaps that stuff you spray on electrical parts to prevent corrosion, then plug everything back in, then silicone around all the plugs to keep moisture out. It sounded like he may have had some corrosion in there causing his computer to "think" a little wacky.

[banditt11]

Hey Bibnflannel. I thought about that. I also heard a show that was talking about the chemical that the spray on the highway in the winter that has the ability to 'wick' into any opening of a wiring harness and move up to 3 foot in length thru the wiring causing corrosion. Very nasty stuff. I will give that a try what you suggested. Never know it might just work. Thanks for the reply :wink:

[Kranky]

Sounds like the accessory relay is sticking in the "on" position.

The accessory relay is usually located behind the dashboard on most trucks. Its function is to energize all the circuits that are switched on & off with the key switch, thereby relieving the key switch itself of the high amp draw required. The key switch activates the accessory relay which turns on , supplying power to the dashboard instruments, computer, and whatever other accessories that are connected to it.

If the accessory relay sticks on, even when you turn the key off, everything will stay turned on.

And if the contacts inside the relay are getting bad, once it does shut off that could lead to problems getting it to turn back on also.

[banditt11]

Ahhh, Splitshift now we're getting somewhere. I was just nosing around in that area and was thinking there had to be some kind of switch because of the way the warning lights would flicker just slightly. At random when I turn the key on and off I can get it to shut off but it is very far and few in between. I will get back under there and see if I can find that relay. Should be marked I would think? Thank you for adding to this puzzle of mine. Have a great weekend.
:wink:
Frank

[banditt11]

Alright went to Freightliner this morning and after 3 hours of searching they found the problem. It was the stinkin qualcom that was sending voltage back thru my electrical system. Seems the power wire and ground got together so to speak and cause my ign and dash lights and warning lights to stay powered up. The qualcom wiring harness was preinstalled on my truck and was not ever used by me. I told them to rip it right out by the roots! :x problem solved.