Author Topic: temp sensor wire - Fixed  (Read 359 times)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
temp sensor wire - Fixed
« on: April 25, 2019, 04:55:01 PM »
My truck has two green wires on the driver's side.  One is for the temp sending unit, and the other runs to the A/C compressor.  IIRC, the one for the compressor is lighter color green.  The sending unit wire also has a protective sleeve over the last few inches of wire, since it is so close to the exhaust manifold.

Do you have a temp sending unit in the driver's side head?  This is the stock location for the gauge sending unit.  There may be other temp sending units for emissions devices, but this one is for the gauge.

Some OEM sending units use a post and straight connector, while older ones like mine use a button fitting on the sending unit and a flat wire connector that slips over it.

Bruce

75gmck25: read your post, I have a 1985 Chevy Scottsdale C20. I am currently doing a complete rebuild of the entire truck. I am presently looking at the electrical connections. I have identified most. One that is driving me crazy in the temp sensor. Everything I have read says a drk grn wire. Your post you indicated two green wires driver side. I have only one for the AC compressor. I have a picture of my stock engine prior to tearing it apart, and like you it shows two green wires. Problem can't find second green wire. Could you possible take a pic of your temp sensor wire at each end, maybe it will help me with this. If I can't find the wire is there any other color chevy may have used for the temp sensor?
 


Thanks 
« Last Edit: May 14, 2019, 08:08:54 AM by Johnret »

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5248
Re: temp sensor wire
« Reply #1 on: April 25, 2019, 05:35:29 PM »
Dark green was the only color used by the factory for the engine coolant temperature sender and ran directly from the firewall bulkhead connector, sharing the convoluted loom running along the driver side flange of the intake manifold with the light green A/C compressor clutch wire.
« Last Edit: April 25, 2019, 05:51:49 PM by bd »
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
temp sensor wire
« Reply #2 on: April 25, 2019, 06:44:15 PM »
I am restoring a 1985 Chevy C20 Scottsdale. It originally came with all kinds of pollution stuff, dual tanks. I am working on the electrical. Everything I have read indicates there should be a dark green wire for the temp sensor. Can't find a dark green wire, is there any other color it might be. Does anyone have a pic of the temo sensor connected or a pic of the wire actually connected? Thanks

Offline JohnnyPopper

  • Frequent Member
  • **
  • Posts: 379
  • Newbie
Re: temp sensor wire
« Reply #3 on: April 26, 2019, 04:39:23 PM »
Wow, if you have an original pic with two green wires, it, or some part of it, has got to be there!

Queue Michael Jackson: 'Got to be there' c. 1971 and take another look....!

Did your rip the harness apart?

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: temp sensor wire
« Reply #4 on: April 29, 2019, 11:23:23 AM »
When I removed the harness I was very careful with in, actually rolled it up and placed it in a plastic bag for safe keeping. Weird thing is, the bulkhead connector doesn't appear to have any broken wires. The only green wires coming out of it is, one connection for the AC compressor, another Green that appears to go to the HEI distributor. Both these green wires have double spade connectors on the ends of them and are keyed correctly for the AC compressor and the HEI distributor. There is two other green wires that are terminated in a round connector that connects to the wiring for the fuel tank selector valve. No other green wires. I have identified all the other wires and there purposes except one wire which is Pink/Black that is in a bundle of wires that are connected to a module on the firewall which I believe is used for the old smog air pumps and control of the recirc system for the exhaust/smog crap. I am at a loss, but also not a a place in my rebuild where I can test and electrical. It's bugging the crap out of me.

Offline JohnnyPopper

  • Frequent Member
  • **
  • Posts: 379
  • Newbie
Re: temp sensor wire
« Reply #5 on: April 29, 2019, 04:06:38 PM »
Bizarre!

Do you know where on the bulkhead connector it's suppose to be?

If you can find that, you can test the temp gauge by tuning on the ignition, and grounding that connection, your needle will ping hot.

Then you will need to run a replacement.

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: temp sensor wire
« Reply #6 on: April 29, 2019, 07:37:15 PM »
Thanks I will try that.

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5248
Re: temp sensor wire
« Reply #7 on: April 29, 2019, 09:16:25 PM »
...The only green wires coming out of [the original harness] is one connection for the AC compressor, another Green that appears to go to the HEI distributor. Both these green wires have double spade connectors on the ends of them and are keyed correctly for the AC compressor and the HEI distributor....

The only factory primary wire that connects to the distributor is pink, which supplies ignition switch controlled 12 volts.  Look at the attached image paying close attention to the pink and dark green wires that are accentuated in color.  I suspect that the green wire you have connected to the distributor is, in fact, the temp sensor wire.  If you reinspect and compare the existing vehicle wiring to the diagram I think you will discover there is a 12-gauge pink wire that either needs a home or is routed to the wrong destination.  Not shown in the image, the A/C compressor harness terminates in a two-wire connector with one dark green wire and one short black wire routed to ground.  That two-wire connector attaches to the compressor clutch.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: temp sensor wire
« Reply #8 on: May 07, 2019, 05:41:48 AM »
Thanks for the reply. I have figured out the Pink wire for the Distributor and placed I correctly. The truck I am restoring came from the west coast, it's original equipment included the pollution stuff, two air pumps, a control module, lots of vacuum lines and pollution piping. the pollution control module has a white wire coming out of it and it is connected in a double spade connector with the only dark green wire in the engine bay. All the wires in the engine bay have been identified except this double spade connector with the green and the white wire. I suspect the green half of this connector is the water temp gauge wire, it goes straight back into the bulkhead connector. I will test it when I get the truck to a point where I have some power in it.

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: temp sensor wire - Fixed
« Reply #9 on: May 14, 2019, 08:10:40 AM »
Well I separated the Grn wire from the white wire in the double connector and connected the green to the temp sensor and "Bingo" the temp gauge started working. Thanks for all the help. On to other problems.