What the heck does this switch do?
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Senior User
Joined: Jul 2005
Posts: 348
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From: Memphis, TN
What the heck does this switch do?
While investigating my injector/idm/pcm performance issue and checking the wiring harness for problems I decided to investigated the 'mystery switch'
When I bought the truck the 2nd owner told me that the switch on the dash (a simple 3 position switch), if pushed up accidently while driving would shutdown the truck. He said he didn't know what it did exactly so he just left it alone. Anyway...I traced this wire down. One wire from fuse box to switch....then from switch to 'somewhere' in the valley under the turbo. I can wiggle it and it is near some other wires that go there from the main harness (where the harness goes from valve cover to valve cover...a small piece splits off and goes down into the valley). Anyway....I can't see where it is attaching without taking 1/2 the truck apart. No clue if this is related to my issue but sure would like to know what it is. The power at fuse box was barely hooked up. I've left it off for now....might have to hook back up if my truck doesn't run.
Anyone have any ideas at all what this switch might have been designed to do? What is under the turbo pedestal to hook to?
When I bought the truck the 2nd owner told me that the switch on the dash (a simple 3 position switch), if pushed up accidently while driving would shutdown the truck. He said he didn't know what it did exactly so he just left it alone. Anyway...I traced this wire down. One wire from fuse box to switch....then from switch to 'somewhere' in the valley under the turbo. I can wiggle it and it is near some other wires that go there from the main harness (where the harness goes from valve cover to valve cover...a small piece splits off and goes down into the valley). Anyway....I can't see where it is attaching without taking 1/2 the truck apart. No clue if this is related to my issue but sure would like to know what it is. The power at fuse box was barely hooked up. I've left it off for now....might have to hook back up if my truck doesn't run.
Anyone have any ideas at all what this switch might have been designed to do? What is under the turbo pedestal to hook to?
Gone, but not forgotten
Joined: Oct 2005
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From: Charlotte-Fairbanks-Bflo
Where is the switch located? I also have a strange switch mounted by the original owner on the lower section of my dash, just above the electric brake controller. It is 3 position too, and no matter what position I put it in seems to do anything. Clueless????
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Senior User
Joined: Jul 2005
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From: Memphis, TN
Mine is lower left of steering column....could be anywhere though. Just a generic looking 3 position switch. I've tested mine before in the driveway and couldn't tell it did anything...but now under further checking...the power to the switch was barely connected in the fuse box. Going to test again shortly.
Senior User
Joined: Mar 2007
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From: St. Clair, MO
maybe a stupid question, but did they have a second fuel tank installed. I've seen switches on the dash to throw between the two. Don't know why it would be going forward though. The exhaust brake suggestion might be more likely. Sounds like a good mystery.
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Joined: Nov 2007
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i have a switch on my dash just to the right of the steering wheel. but i know what it does. its for my exhaust brake. I also have two switches one to the front of the truck and one to the rear and they are power switches to a wentch plug on both front and rear so maybe they had a wentch in the fron and that was a switch for it...not likely but just another explanation.
Post Fiend
Joined: Jul 2005
Posts: 14,582
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From: 21791
If it shuts down the truck quickly, without "choking" the truck out, it's probably some sort of deal which opens the circuit to the IPR. With no voltage to the IPR, it remains open. The pressure doesnt build, injectors don't fire, truck stops.
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Fleet Mechanic
Joined: Sep 2006
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From: IN
The other owner may have tied in as Kris said to the IPR circut as an easy anti-thieft device to keep thieves from taking the truck. Who knows I would unhook it if the truck runs fine with out it I would leave it off if not hook it back up sounds hard to get to the other end to disconnect it.
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Thread Starter
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Senior User
Joined: Jul 2005
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From: Memphis, TN
Well....I found it. First...the reason it didn't work was power was barely connected. So...in the middle position....normal. In the up position.....exhaust brake (loud hissing noise from turbo area...I assume that is an exhaust brake) It doesn't seem to work that well however.
So..the winner is pushingXtheXedge. Thanks for all the help....now if I could only get my original problem solved.
THANKS
So..the winner is pushingXtheXedge. Thanks for all the help....now if I could only get my original problem solved.
THANKS
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Senior User
Joined: Jul 2005
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From: Memphis, TN
Originally Posted by strokin_it7.3
But, an exhaust brake won't kill the engine.
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Joined: Nov 2007
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with my exhaust brake it drop the rpm significantly so that may have been what he was talking about but it doesn't completly shut off the engine. who knows, as long as your truck runs good i guess thats what counts.