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Old 03-15-2009, 09:43 AM   #1
Green Monster
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Question Need help with wiring stock temperature and vacuum gauges

Gentlemen,

I would like some help on how to wire stock temperature gauge and vacuum gauge. The previous owner installed a SunPro temperature gauge where the stock gauge should be. I want to convert this back to stock and I figured while I'm spending the money and time doing this, I might at well upgrade the cluster to house a vacuum gauge.

  1. Do I need to look for existing wires or install new ones to get the stock temp gauge to work?
  2. What do I need to do to get my vacuum gauge to work?



This is the gauge that is currently in the truck.


This is temperature wire coming through the firewall.


This is the wire going into the, sending unit (correct me if I'm wrong). See very center of photograph with the white teflon threads?.



I have all the stock gauges and will repaint the needles. On order through www.cs-m.com I have the vacuum gauge setup (VG101 pictured below). This includes a new bezel, lens (with vac), and black faceplate (with vac).

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Old 03-15-2009, 10:43 AM   #2
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Re: Need help with wiring stock temperature and vacuum gauges

That Sunpro is more of a manual unit, take the sending unit out and replace with an electric unit. Mine is located up on the intake, I was worried about burning the wire down around the headers...green wire comes across top of cowl and enters firewall harness at top left side, second wire in. I would lend ya my wiring diagram, but I'm using it rite now...

Hopefully, the PO didn't cut the wire and just tucked it up someplace

As far as the vac. goes, I'll watch you since I have to do it also. lol



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Old 03-15-2009, 04:09 PM   #3
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Re: Need help with wiring stock temperature and vacuum gauges

Thanks for the pics Jaros44sr. That helps a lot. I'll be working on my Blazer tomorrow so I'll be able to investigate what is there.

So I will need an electric sending unit. I'll try Pep Boys or some other parts store.

Do I need another wire to complete the loop or is the green wire the only wire I'm dealing with?


As for the vacuum, I was told by Gary Terry of www.cs-m.com that I need to run a tube from the gauge through the firewall to a hose the goes from the intake manifold to the A/C. Then tap into the line by adding in a "T". I was just curious if anyone had some info about it while I was asking about the temp. gauge.
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Old 03-15-2009, 10:19 PM   #4
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Re: Need help with wiring stock temperature and vacuum gauges

Quote:
Originally Posted by Green Monster View Post
Thanks for the pics Jaros44sr. That helps a lot. I'll be working on my Blazer tomorrow so I'll be able to investigate what is there.

So I will need an electric sending unit. I'll try Pep Boys or some other parts store.

Do I need another wire to complete the loop or is the green wire the only wire I'm dealing with?


As for the vacuum, I was told by Gary Terry of www.cs-m.com that I need to run a tube from the gauge through the firewall to a hose the goes from the intake manifold to the A/C. Then tap into the line by adding in a "T". I was just curious if anyone had some info about it while I was asking about the temp. gauge.
Standard temp. sending unit, and yes the green wire should go all the way to the gauge IIRC

Post up pics. on your progress...we all like pics. to look at
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Old 03-15-2009, 10:58 PM   #5
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Re: Need help with wiring stock temperature and vacuum gauges

When you go to the auto parts store to buy the sending unit they'll probably ask you "idiot light" or "gauge"--you want "gauge".

I'm guessing GM used a hard line for the vacuum gauge on our trucks, but by the late '70s they were using rubber hose so that is an option.
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Old 03-16-2009, 08:03 AM   #6
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Re: Need help with wiring stock temperature and vacuum gauges

Jaros- I really owe you guys some pics. I'm overhauling my interior and making it look showroom fresh. I'm waiting for the instrument cluster parts to show up, then I'll get started on the vacuum and temp gauges.

BadPeanut- Thanks for the tip on requesting the sending unit and vacuum hose.
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Old 03-16-2009, 08:11 AM   #7
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Re: Need help with wiring stock temperature and vacuum gauges

Subsribing, 'cause I can't get enough of the Green Monster...
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Old 03-17-2009, 06:29 PM   #8
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Re: Need help with wiring stock temperature and vacuum gauges

Status update:

I purchased a new sending unit. BadPeanut's advice on "gauge or dummy light" was quite useful as I was asked which one I needed. Whew! Crisis averted on buying the wrong part as electrical parts are non returnable at Schlep Boys. I looked at the gauge and it came with a black plastic clip like the white plastic clip pictured in Jaros ride.


I can't find my green wire. In the engine compartment I see the wire coming out of the bulkhead connector then it is wrapped up into a bundle of wires. The bundle follows the firewall along the cowl then drops down the firewall on the passenger side engine then I'm not sure where that bundle goes or where the green wire is supposed to come out of the bundle. I may have to look around some more. Any advice?

In the passenger compartment I don't know where the green wire is. Is it supposed to come out of the fuse block or something?

Pictures would be extremely helpful.
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Old 03-21-2009, 07:03 PM   #9
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Re: Need help with wiring stock temperature and vacuum gauges

I"m stuck here guys...

Can someone snap a picture of how the wiring looks going to the temp gauge? Where does it come from?
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Old 03-22-2009, 07:35 AM   #10
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Re: Need help with wiring stock temperature and vacuum gauges

Bump

Can anyone take two pictures of what the back of the temp gauge looks like from under the dash. I need one shot of the back side of the gauge and on where the green wire goes to in the firewall or fuse block (not sure if if even goes to either one).

As you can see, I'm lost. I'm trying to put this back to stock and need your help doing so.
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Old 03-22-2009, 09:21 AM   #11
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Re: Need help with wiring stock temperature and vacuum gauges

Quote:
Originally Posted by Green Monster View Post
Bump

Can anyone take two pictures of what the back of the temp gauge looks like from under the dash. I need one shot of the back side of the gauge and on where the green wire goes to in the firewall or fuse block (not sure if if even goes to either one).

As you can see, I'm lost. I'm trying to put this back to stock and need your help doing so.
I don't fit under my dash, but I will try to give you as much info as I can get from the wiring diagram...

Your gauge is hooked up to the printed circuit board, the board has a connector, and into that is plugged the 1/2 round plug around the steering column. Circuit 35 A & B, Dark Green on the diagram, tied into the ign. switch at the ground 1 or ground 2 position( I'm thinking ground 1).

From there it should be headed towards the fuse block, just keep looking for dark green

Basically, it looks like it starts at the ign. sw., goes to the connector for the circuit board down to the big 1/2 round connector at the steering column and from there to the fuse block. Make sure you follow the 20 gauge wire as there is a 12gauge wire for the horns that is also dk. grn.

Or give me a call on my cell, or drive a 1/2 hour north...202
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Last edited by jaros44sr; 03-22-2009 at 09:36 AM.
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Old 03-23-2009, 08:30 AM   #12
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Re: Need help with wiring stock temperature and vacuum gauges

Thank you. I'm heading out to work on it today. I'll see what I can find and snap any pics if things start looking too confusing.

Thanks for the offer to come up. I definitely will make my way up to see you and seek some help getting this wiring straightened out if I get really stuck.
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Old 03-23-2009, 08:15 PM   #13
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Re: Need help with wiring stock temperature and vacuum gauges

Not a good pic, but here is how all of mine are installed. I drew in the temp sender wire going to the temp sensor in the head. The green wire just comes out of the bulkhead connector and in the passenger compartment it runs like Jaros said.
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Old 03-29-2009, 08:34 AM   #14
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Re: Need help with wiring stock temperature and vacuum gauges

Find anything? How's the progress coming
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Old 03-29-2009, 09:11 AM   #15
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Re: Need help with wiring stock temperature and vacuum gauges

I can't find the old wire in the passenger cabin. I'm going to come back to it soon.

How does the wire fit into the plastic clip that fits over the sending unit shown in post no. 2? Is there a flat male connector crimped onto the wire inside there?

Right now I'm dealing with a little unforeseen problem with my ignition switch bezel swap. I got a little anxious by trying to take the bezel off without taking the ignition lock cylinder out and jammed my ignition to the point where it won't turn. I ordered a ignition bezel removal tool which just arrived yesterday. Once I get that straightened out then I will return to the temp sensor. I received the new instrument panel, lens, and vacuum gauge so I'm looking forward to installing them and brightening up the dash.
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Old 03-29-2009, 09:22 AM   #16
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Re: Need help with wiring stock temperature and vacuum gauges

The green wire should be built into your main harnass that clips onto the back of your dash bezel. You "should" just need to hook up the printed circuit on the back to the new gauge. And in the engine compartment just run a new wire to the temp sender up to what you can find left on the firewall plug, just be sure it's the right one. There are colored diagrams in the FAQ portion of the forums.

As far as vacuum you can run off of many areas, depends on your carb but there could be a "full vacuum" port on it, or a plug on top of you intake manifold, brake booster or something going to your A/C as described. Just don't use the one going to your distributor advance, it only opens under throttle, not idle...
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Old 03-29-2009, 09:29 AM   #17
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Re: Need help with wiring stock temperature and vacuum gauges

I will say you guys have e running out to check out mine ..my under hood wiring is a mess os stuff going everywhere but now where???? theres alot of wires just hanging

is there an online diagram of color codes and where they go..mine is and A/C truck which I think is worse...and my Vacum lines ....ahhhhhhh
but your pics are helping

thanx Jeff
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Old 03-29-2009, 09:36 AM   #18
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Re: Need help with wiring stock temperature and vacuum gauges

Quote:
Originally Posted by Green Monster View Post
I can't find the old wire in the passenger cabin. I'm going to come back to it soon.

How does the wire fit into the plastic clip that fits over the sending unit shown in post no. 2? Is there a flat male connector crimped onto the wire inside there?
Yes...

Well, I was afraid you were going to ask that I had to send my harness back to M&H for some mod. work, I didn't want to break that connector, so I left my sending unit on there. They must of thought I was a real moron...

The best that I can see is, if you take a thin flat pc. of metal and push it in from the front of the connector it will depress a metal spring clip that is part of the connector. This will allow you to separate it from the sending unit. The clip that you want to depress is on the top side. Good luck, and lmk if it works There has to be a tool to do this

I'll try to get a better pic., there is probably a button on this camera to get a better closeup, but I never read the manual. I just put it on automatic

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Old 03-29-2009, 10:02 AM   #19
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Re: Need help with wiring stock temperature and vacuum gauges

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Originally Posted by Tynee View Post
Subsribing, 'cause I can't get enough of the Green Monster...
Just check out E-bay, it's on there alot Sorry, just had to say it
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Old 03-30-2009, 08:00 AM   #20
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Re: Need help with wiring stock temperature and vacuum gauges

The problem with my clip is not how to take it off, it's that there is nothing in it. It looks like a piece of metal that is bent like a "V" inside yours. I'm going to work on it today...
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Old 03-30-2009, 08:25 AM   #21
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Re: Need help with wiring stock temperature and vacuum gauges

Quote:
Originally Posted by Green Monster View Post
The problem with my clip is not how to take it off, it's that there is nothing in it. It looks like a piece of metal that is bent like a "V" inside yours. I'm going to work on it today...
Oh, OK, misunderstood ya...
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Old 03-30-2009, 08:26 AM   #22
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Re: Need help with wiring stock temperature and vacuum gauges

All it is, is a terminal lug, or spade if you want to call it that, inside the plastic housing. You just slide it over the tip of the temp sensor and the "spade" clamps onto the sensor. I would be surprised if the plastic housing is still there if its original.
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Old 03-31-2009, 12:42 PM   #23
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Re: Need help with wiring stock temperature and vacuum gauges

Terminmal spade... thanks. NAPA or other parts store should have these, right?

I traced the green wire into the engine compartment from the bulkhead connector. I found it laying on the transmission bell housing cut off with the end wrapped in electrical tape. I also found a cut off yellow wire coming from the same wire harness about 12 inches from the cut green wire. The wires are in a braided heat sheilded sheeth. Does anyone know what the yellow wire is suppossed to go to?

I'm having a hard time finding the green wire in the passenger compartment. It appears to come through the firewall then go to a connnector located on the steering column near the firewall. Am I tracing the correct wire here? If so, where do the wires on the steering column connector go from there?
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Old 03-31-2009, 06:36 PM   #24
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Re: Need help with wiring stock temperature and vacuum gauges

There's two green wires down there. One goes to the horn relay right above the steering column. The other one is running from the bulkhead connector and then I think to the ignition switch then up into the connector for the back of the dash printed circuit. There is a color coded wiring diagram here:
http://67-72chevytrucks.com/vboard/s...d.php?t=185665

I can't open it from work here, but you can look and see what your yellow wire is too. May be the coil wire cut off if you have been upgraded to HEI, not sure. Good luck!! Jeff.
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Old 03-31-2009, 06:44 PM   #25
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Re: Need help with wiring stock temperature and vacuum gauges

Yep, just verified it on the original drawing here:
http://www.geocities.com/chevroletc1070/wiringdias.html

It does run thru the ignition switch then right up to the dash connector. So, key has to be on for it to work, remember that in your troubleshooting.

Jeff.

Oh, and any terminal spade will work as long as its the kind of u-shaped one. You can get them at Napa, Wal-mart or anywhere that sells connectors.
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