Mystery Wires Help Please - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hessian18 · 06-29-2008, 01:04 AM

I cannot for the life of me figure what exactly these wire are for....and also this small sensor....

Its on the driver side toward the rear of the head....

Its an Inline 250.....

From what I have found the greenwire is the temp sensor wire ?? The other wire is orange with a black line.....

I have replaced the temperature switch....is this different from the temp sensor ??

My gauge just goes slowly until its pinned out....If I ground it out...it goes instantly.....Im confused LOL

jrsmith_2010 · 06-29-2008, 01:19 AM

hmmmmm, idk, could it be a sensor for the AC?

hessian18 · 06-29-2008, 01:22 AM

Im not sure....

I did figure out where the idle up solenoid wire went for the A/C.....

Im just wondering why my temp gauge is still acting up...

Thats not a oil pressure switch is it ??

70LonghornCST · 06-29-2008, 01:24 AM

What I am seeing in your pics are two sensors. The one on the block is an oil pressure
sensor, the one on the water neck is the heat/water temp sensor. I am not sure which wires go to which. You may need do trial and error. You wont mess anything up if they're crossed, I believe.

jrsmith_2010 · 06-29-2008, 01:26 AM

i agree, trial and error is the way to go to figure it out.

Big68 · 06-29-2008, 01:40 AM

The sensor is definitely a water temp sensor, and that is what the green wire goes to.

As for the other wire, I'm not sure. Have you tried to trace it and see where it ends up?

hessian18 · 06-29-2008, 01:44 AM

Quote:

Originally Posted by 70LonghornCST

What I am seeing in your pics are two sensors. The one on the block is an oil pressure
sensor, the one on the water neck is the heat/water temp sensor. I am not sure which wires go to which. You may need do trial and error. You wont mess anything up if they're crossed, I believe.

So that small sensor is also a temp sensor ??

I couldnt find anything like it at the parts store....

The orange wire with the black stripe goes back into the loom with the green wire...I havent gone any further into the loom...

Big68 · 06-29-2008, 02:01 AM

Quote:

Originally Posted by hessian18

So that small sensor is also a temp sensor ??

I couldnt find anything like it at the parts store....

I'm almost certain that the small sensor is also a temp sensor. I've gotten into many vehicles that had two even [U]three[U] temp sensors. It seems that a PO will just keep adding them wherever they can. A quick way to see if it's a water temp sensor or an oil pressure sensor is to take it out and see what kind of fluid comes out. If it's an oil pressure sensor there probably won't be anything come out unless you leave it running. (not recommended!), but you'll be able to see oil on the end of it.

I've got a '65 250 I-6 in my '68 GMC, and the boss for the oil pressure is on the passenger side right under the side cover at the rear of the motor. That doesn't mean that GM didn't change locations, but I don't think they'd put it in the head.

70LonghornCST · 06-29-2008, 02:57 AM

Quote:

Originally Posted by Big68

I'm almost certain that the small sensor is also a temp sensor. I've gotten into many vehicles that had two even [U]three[U] temp sensors. It seems that a PO will just keep adding them wherever they can. A quick way to see if it's a water temp sensor or an oil pressure sensor is to take it out and see what kind of fluid comes out. If it's an oil pressure sensor there probably won't be anything come out unless you leave it running. (not recommended!), but you'll be able to see oil on the end of it.

I've got a '65 250 I-6 in my '68 GMC, and the boss for the oil pressure is on the passenger side right under the side cover at the rear of the motor. That doesn't mean that GM didn't change locations, but I don't think they'd put it in the head.

Yes, that is right. In retrospect of Big68's post, I agree. The oil sensor is located on the opposite side (passengers). The small sensor located on the driver side of the block below the valve cover IS a water/temp sensor also. The larger brass colored one on the water neck is an aftermarket type. You certainly have 2 installed. When I had my last truck with an inline 6, I installed an aftermarket gauge on the waterneck. I wanted to get rid of the warning light since it is Hot in the central California valley Where I live.

hessian18 · 06-29-2008, 05:41 PM

Well now im real confused....

Both of these sensors are in factory locations with factory wiring...If you pull the wiring back its all in the stock loom with the original GM tape and everything LOL

I cant find that little sensor anywhere......only sensors I have found that are Tu65 Tu66 which are for the water neck......

hmmmm

GMBowtie79 · 06-29-2008, 06:48 PM

Pull it out, it's probably a oil sensor. Try hooking the wire with the orange connector on it to that sensor it looks like it is very close to where the wire would end length wise and it has the correct type of end on it. the sensor in the water neck looks like one for a light not a gauge. I just went through that conversation with the guy at the parts store last weekend P/o of my truck had the wrong one in mine and the gauge wouldn't work properly. Changed it and it works now. Dissconnect the waterneck one and hook up the other one and see what happens.

hessian18 · 06-29-2008, 06:57 PM

Im going to pull it out tonight when the motor cools off....

Im trying to find a wiring diagram...so far no luck...

hessian18 · 06-30-2008, 09:03 PM

Well I pulled the sensor today....It IS a coolant sensor....

I tried testing it with a DVOM but wasnt showing anything....

The part number is 14025299 1028...that is stamped into it.....

I cant find that part number on any websites....

I also traced the wires more back into the loom...both wire going to these sensors are green......

The orange and black wire is still a mystery LMAO !!

GMBowtie79 · 06-30-2008, 10:10 PM

I was just reading a article that was on sensors maybe this will help. Its down a little bit it talks about troubleshooting temp gauges.Follow the link in this post.
http://67-72chevytrucks.com/vboard/s...9&postcount=23

That orange wire looks similer in size to the orange one on mine that goes down tward the tranny. I believe it might be for the reverse light switch. I could be wrong, mine is a 79 with a manual tranny and it's to low to crawl under and look.

PhilaTruck · 07-01-2008, 09:49 PM

The oil pressure sensor is at the back on top of the engine, behind the intake, right of the dizzy. Common leak spot.

GMBowtie79 · 07-01-2008, 10:56 PM

Quote:

Originally Posted by PhilaTruck

The oil pressure sensor is at the back on top of the engine, behind the intake, right of the dizzy. Common leak spot.

THats where it is on a V8 this is a 250 I6.

hessian18 · 07-02-2008, 01:40 AM

Thanks guys for all the help....

I have not been able to find this small sensor anywhere....( checking car quest tomorrow)

Im just going to say forget it LMAO !!! The Gen III will be dropped in shortly....(hahahaha) doubt it......

I wish I had some time

GMBowtie79 · 07-02-2008, 12:05 PM

Did you try disconnecting the one in the waterneck and puting the green wire on the small sensor Just to see if it works?

hessian18 · 07-19-2008, 08:29 PM

I have tryed both....

The smaller sensor is the one I cant find anywhere.....

All the truck books and parts stores are showing the bigger temp switch in the water neck.......For my year truck and make...

I did trace BOTH this green wire and orange wire back to the oil pressure switch.....so the orange wire has to do with the oil pressure switch and so does this green wire-coolant sensor......

I cant find anywhere within the length of the orange wire to hook it up....LOL

I just want my choke light off LOL

Any body have the 81 light duty service manual ??

hessian18 · 11-19-2008, 11:24 PM

Well my choke works perfectly, since its getting colder now.... I figured it wouldnt work at all since the light is on.....

Strange....I still havent figured it out

Shouldnt be to much longer until the swap is started....

hessian18 · 11-25-2008, 07:14 PM

Any other input on this ??

Thanks

Bobby

PhilaTruck · 12-14-2008, 09:41 PM

Electric choke? Check the resistance.

06-29-2008, 01:04 AM	#1
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Mystery Wires Help Please I cannot for the life of me figure what exactly these wire are for....and also this small sensor.... Its on the driver side toward the rear of the head.... Its an Inline 250..... From what I have found the greenwire is the temp sensor wire ?? The other wire is orange with a black line..... I have replaced the temperature switch....is this different from the temp sensor ?? My gauge just goes slowly until its pinned out....If I ground it out...it goes instantly.....Im confused LOL __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon... Last edited by hessian18; 06-29-2008 at 01:06 AM.

06-29-2008, 01:19 AM	#2
jrsmith_2010 I like turtles... Join Date: May 2008 Location: Kansas Posts: 993	Re: Mystery Wires Help Please hmmmmm, idk, could it be a sensor for the AC?

06-29-2008, 01:22 AM	#3
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Im not sure.... I did figure out where the idle up solenoid wire went for the A/C..... Im just wondering why my temp gauge is still acting up... Thats not a oil pressure switch is it ?? __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon... Last edited by hessian18; 06-29-2008 at 01:23 AM.

06-29-2008, 01:24 AM	#4
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: Mystery Wires Help Please What I am seeing in your pics are two sensors. The one on the block is an oil pressure sensor, the one on the water neck is the heat/water temp sensor. I am not sure which wires go to which. You may need do trial and error. You wont mess anything up if they're crossed, I believe. __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

06-29-2008, 01:26 AM	#5
jrsmith_2010 I like turtles... Join Date: May 2008 Location: Kansas Posts: 993	Re: Mystery Wires Help Please i agree, trial and error is the way to go to figure it out.

06-29-2008, 01:40 AM	#6
Big68 Registered User Join Date: May 2008 Location: Macon, Ga Posts: 15	Re: Mystery Wires Help Please The sensor is definitely a water temp sensor, and that is what the green wire goes to. As for the other wire, I'm not sure. Have you tried to trace it and see where it ends up? __________________ 1968 GMC, 2wd to 4wd conversion, automatic to manual, 4 in custom lift, 36'' military tires, recent 454 upgrade 1979 Pontiac Firebird, mildly built sb 350, t56 trans

06-29-2008, 05:41 PM	#10
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Well now im real confused.... Both of these sensors are in factory locations with factory wiring...If you pull the wiring back its all in the stock loom with the original GM tape and everything LOL I cant find that little sensor anywhere......only sensors I have found that are Tu65 Tu66 which are for the water neck...... hmmmm __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon... Last edited by hessian18; 06-29-2008 at 05:41 PM.

06-29-2008, 06:48 PM	#11
GMBowtie79 Surviving, one day at a time! Join Date: Jan 2008 Location: Turlock,CA Posts: 295	Re: Mystery Wires Help Please Pull it out, it's probably a oil sensor. Try hooking the wire with the orange connector on it to that sensor it looks like it is very close to where the wire would end length wise and it has the correct type of end on it. the sensor in the water neck looks like one for a light not a gauge. I just went through that conversation with the guy at the parts store last weekend P/o of my truck had the wrong one in mine and the gauge wouldn't work properly. Changed it and it works now. Dissconnect the waterneck one and hook up the other one and see what happens. __________________ 79 Burb,350,tremic 5 spd, 4 wheel disc, daily driver 74 swb,350,350,driver & future project "There's no such thing as a finished project" Last edited by GMBowtie79; 06-29-2008 at 06:55 PM.

06-29-2008, 06:57 PM	#12
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Im going to pull it out tonight when the motor cools off.... Im trying to find a wiring diagram...so far no luck... __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon...

06-30-2008, 09:03 PM	#13
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Well I pulled the sensor today....It IS a coolant sensor.... I tried testing it with a DVOM but wasnt showing anything.... The part number is 14025299 1028...that is stamped into it..... I cant find that part number on any websites.... I also traced the wires more back into the loom...both wire going to these sensors are green...... The orange and black wire is still a mystery LMAO !! __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon...

06-30-2008, 10:10 PM	#14
GMBowtie79 Surviving, one day at a time! Join Date: Jan 2008 Location: Turlock,CA Posts: 295	Re: Mystery Wires Help Please I was just reading a article that was on sensors maybe this will help. Its down a little bit it talks about troubleshooting temp gauges.Follow the link in this post. http://67-72chevytrucks.com/vboard/s...9&postcount=23 That orange wire looks similer in size to the orange one on mine that goes down tward the tranny. I believe it might be for the reverse light switch. I could be wrong, mine is a 79 with a manual tranny and it's to low to crawl under and look. __________________ 79 Burb,350,tremic 5 spd, 4 wheel disc, daily driver 74 swb,350,350,driver & future project "There's no such thing as a finished project" Last edited by GMBowtie79; 06-30-2008 at 10:25 PM.

07-01-2008, 09:49 PM	#15
PhilaTruck Right on the line, baby! Join Date: Oct 2003 Location: Phila, PA 19130 Posts: 1,486	Re: Mystery Wires Help Please The oil pressure sensor is at the back on top of the engine, behind the intake, right of the dizzy. Common leak spot. __________________ 83 GMC 406 th400/3.73 Eaton Truetrac posi, headers, x pipe, & racePros. Tubular control arms, lowering rear springs, caltracs. Still ugly, but getting built right, although slowly Click and scroll down for site vendors! Subscribe here!

07-02-2008, 01:40 AM	#17
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Thanks guys for all the help.... I have not been able to find this small sensor anywhere....( checking car quest tomorrow) Im just going to say forget it LMAO !!! The Gen III will be dropped in shortly....(hahahaha) doubt it...... I wish I had some time __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon... Last edited by hessian18; 07-02-2008 at 01:40 AM.

07-02-2008, 12:05 PM	#18
GMBowtie79 Surviving, one day at a time! Join Date: Jan 2008 Location: Turlock,CA Posts: 295	Re: Mystery Wires Help Please Did you try disconnecting the one in the waterneck and puting the green wire on the small sensor Just to see if it works? __________________ 79 Burb,350,tremic 5 spd, 4 wheel disc, daily driver 74 swb,350,350,driver & future project "There's no such thing as a finished project" Last edited by GMBowtie79; 07-02-2008 at 12:06 PM.

07-19-2008, 08:29 PM	#19
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please I have tryed both.... The smaller sensor is the one I cant find anywhere..... All the truck books and parts stores are showing the bigger temp switch in the water neck.......For my year truck and make... I did trace BOTH this green wire and orange wire back to the oil pressure switch.....so the orange wire has to do with the oil pressure switch and so does this green wire-coolant sensor...... I cant find anywhere within the length of the orange wire to hook it up....LOL I just want my choke light off LOL Any body have the 81 light duty service manual ?? __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon... Last edited by hessian18; 07-19-2008 at 08:56 PM.



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11-19-2008, 11:24 PM	#20
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Well my choke works perfectly, since its getting colder now.... I figured it wouldnt work at all since the light is on..... Strange....I still havent figured it out Shouldnt be to much longer until the swap is started.... __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon...

11-25-2008, 07:14 PM	#21
hessian18 Gen III Power Join Date: Sep 2007 Location: Hesperia CA Posts: 318	Re: Mystery Wires Help Please Any other input on this ?? Thanks Bobby __________________ ---Bob--- '81 Long Box. 2005 5.3l Vortec and 2005 4L80e coming soon...

12-14-2008, 09:41 PM	#22
PhilaTruck Right on the line, baby! Join Date: Oct 2003 Location: Phila, PA 19130 Posts: 1,486	Re: Mystery Wires Help Please Electric choke? Check the resistance. __________________ 83 GMC 406 th400/3.73 Eaton Truetrac posi, headers, x pipe, & racePros. Tubular control arms, lowering rear springs, caltracs. Still ugly, but getting built right, although slowly Click and scroll down for site vendors! Subscribe here!

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