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Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 9824
Experience:  34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
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Working on a 2000 Peterbilt 379 Upon turning the ignition

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Working on a 2000 Peterbilt 379: Upon turning the ignition key, the warning lights, buzzer, heater fan and gauges including tach, speedometer and trip meter will not work. This was random but has now failed completely. I'm assuming the key switch is bad. How can I bypass the key switch so to allow my gauges to work until I can replace the key switch? Also, I have always had in intermittent click when trying to start the truck. The truck starts fine and runs fine. The radio work fine too with the key on.
Hi I'm Wayne,
I will try to help you with this,
your not going to like what I say, no you can not by-pass all instruments, PER LAW, yes you can in emergency by pass to get truck running, and off road, jump big red wire to small I think blue or black wire this will hot wire your truck (FOR EMERGENCY ONLY), touch big red wire to I think blue, and truck will start, . ADVISE EMERGENCY ONLY, THIS IS A SAFTEY HASARDY. I am not, in no way, to advise you, drive this truck this way.

get back to me. Surprised
Wayne and other Heavy Equipment Specialists are ready to help you
Customer: replied 7 years ago.
The truck starts and runs. The issue is, when I turn the key, the dummy lights don't come on, the beeper does not sound, the gauges don't work and the heater/blower fan does not work. The radio works fine as it is apparently on a different circuit. It appears as though the key/switch is not allowing power to the accessories thus disallowing my guages to work. This was random as I could jiggle the key/switch, though now I can't get the accessories to work and jiggling the key does not remedy it... It seems there is something internal that has gone bad? What is the remedy? Is there a wire from the key/switch on the back, perhaps one of the terminals which is not getting juice from the terminal on the back of the key/switch? If so, can this wire run directly off the push button so to allow power to the gauges?
HI Tim nrob,

I am going gto opt-out, miss read your question, I believe you have other problems, we have a lot of good experts on line and they wil be able to help you.

Thanks for giving me a chance.

Customer: replied 7 years ago.
Thanks anyway.

hang in their , some one will grab it.

one other expert told me you have a bad rely for gauge cluster???
Customer: replied 7 years ago.
Yes, I believe that may be it. I thought the key/switch looks like a relay in-itself. But, if the issue is a "bad relay for gauge cluster" does this relay also control the heater fan? That seems odd, but I suppose it is possible :)

Thanks for the comeback. Hope someone chimes in.

I don't believe it's your IGN switch, and radio is on separate system,
Why don't you swap around relays with another and try that, I do not want to opt back in then that would tie this question back to me,

Customer: replied 7 years ago.
Ok. I'm assuming the relay is within the fuse box? Looking at the diagram on the fuse box, there is no relay listed for the guage cluster. Oddly enough, I have two additonal switches "after market" that don't work as well. I'm assuming the mechanic, years ago, ran these switches off the same power source as they only work with the key on. I'll go out to the truck and start swapping relays and see what I can find. Thanks again.
Customer: replied 7 years ago.
I figured it out. On the far drivers side, behind the dash is a relay. Attached to it are two white heavy gauge wires along with multiple small wires. One of the terminals which one the white wire is connected to is loose internally on the relay. I can reproduce the "short" as it is by wiggling the wire on the terminal causing it to short out. At the same time, I believe this may be related to the random click I get when attempting to start the truck. Whatever the case, we win!Smile Thanks for your help!

I am glad you found it, good job, Happy trucking

Thank you for the Accept, WayneCool