What is the yellow wire for? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**rs74** · 02-16-2015, 09:03 PM

I did alot of work today on the diesel short bed and came across this. The yellow wire has been cut but not sure where it is supposed to go. Trying to get all the little things taken care of and wondering if I need to do something with this.

**Corts60** · 02-17-2015, 10:10 AM

Looks like an accessory 12v + wire. Probably someone added it over the years to send power somewhere else.

**rs74** · 02-17-2015, 10:13 AM

Quote:

Originally Posted by Corts60

Looks like an accessory 12v + wire. Probably someone added it over the years to send power somewhere else.

Thanks. Trying to get all the small things figured out on this truck. I won't worry about the wire then. Just take it off. Now I have to see about why sometimes it wants to have a normal high idle on start up and other times it has a really low idle and sometimes dies. Then figure out why it smokes soo much on start up and warm up.

68post · 02-17-2015, 10:42 AM

Sorry but I'm not familiar with what is OEM - but that is possibly part of the glow plug circuit either OEM or added on. !?

**Corts60** · 02-17-2015, 06:41 PM

Quote:

Originally Posted by rs74

Thanks. Trying to get all the small things figured out on this truck. I won't worry about the wire then. Just take it off. Now I have to see about why sometimes it wants to have a normal high idle on start up and other times it has a really low idle and sometimes dies. Then figure out why it smokes soo much on start up and warm up.

You probably have a cold idle solenoid on the injection pump. It is also used to bump the idle up when the heater controls are placed in Defrost or AC position to help with the load of the compressor.

If you have lots of white smoke on start up you more than likely have a/some failed glow plugs. If it's blue smoke you're burning oil.

reporter000001 · 02-18-2015, 01:20 AM

does it come from the junction block? or did some one drill a hole? my book says speed switch relay closed above 900rpm.

but this book isnt accuate for diesel...perfect for gas... i found this info in the straight6 section .......so no guarntees......

**Corts60** · 02-18-2015, 09:47 AM

Quote:

Originally Posted by reporter000001

does it come from the junction block? or did some one drill a hole? my book says speed switch relay closed above 900rpm.

but this book isnt accuate for diesel...perfect for gas... i found this info in the straight6 section .......so no guarntees......

Not the same thing.

02-16-2015, 09:03 PM	#1
rs74 Senior Member Join Date: Jun 2010 Location: Illinois Posts: 2,957	What is the yellow wire for? I did alot of work today on the diesel short bed and came across this. The yellow wire has been cut but not sure where it is supposed to go. Trying to get all the little things taken care of and wondering if I need to do something with this. Attached Images __________________ Roy 85 Short Bed Silverado- Work in progress. http://67-72chevytrucks.com/vboard/s...d.php?t=564818 1987 R10 shortie

02-17-2015, 10:10 AM	#2
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: What is the yellow wire for? Looks like an accessory 12v + wire. Probably someone added it over the years to send power somewhere else. __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold)

02-17-2015, 10:42 AM	#4
68post Registered User Join Date: Jan 2014 Location: Indpls. , IN Posts: 795	Re: What is the yellow wire for? Sorry but I'm not familiar with what is OEM - but that is possibly part of the glow plug circuit either OEM or added on. !? __________________ Tim K. 84 K30 srw Silverado 454 auto 85 C20 350 C6P auto flatbed 94 K1500 lifted shortbed 350 4 bbl NV4500

02-18-2015, 01:20 AM	#6
reporter000001 Registered User Join Date: Feb 2015 Location: Fresno Posts: 34	Re: What is the yellow wire for? does it come from the junction block? or did some one drill a hole? my book says speed switch relay closed above 900rpm. but this book isnt accuate for diesel...perfect for gas... i found this info in the straight6 section .......so no guarntees......



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