1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

[Monte M.]

I am working on a 1972, LS-5. I am trying to find the wire that goes from the TCS switch to the heat sensor on the passengers head.

Typically on a small block, there is a connector that the "TCS jumper" plugs into and from there the other end goes to the heat sensor in the passenger head.

I guess, if I understood correct, there was a question if the big blocks ever had an extra wire as a jumper. It came right out of the harness and plugged right into the heat sensor in the passenger side head.Can anyone confirm this? From what I understand, it was never resolved if any of them went straight to the sensor in the head.

My personal issue is: From the main wiring harness, there is a smaller harness that comes off and plugs into the TCS switch on the intake manifold.

The tan wire in one side of the plug has another tan wire coming off the plug going to the fast idle solenoid, as it should.
The blue wire one the other side of the plug has another wire coming off of it too. That wire goes back into the main harness, AND SHOULD GO OVER TO THE HEAT SENSOR IN THE SIDE OF THE PASSENGERS HEAD, BUT IT DOES NOT. I have gone as far as unplugging everything on the main harness on the passenger side of the distributor cap. I have that whole part of the main harness loose enough to see there is not a cut wire or something like that.

This is the rough part. This is a low mileage car that has every harness still in tact and everything on the car work the way it should. Except the TCS system due to this missing wire.

Anyway, the blue wire comes off the TCS switch and goes back into the main harness. Although a dark blue wire does continue to go in the main harness in the direction of the passenger side, it is not the dark blue wire am looking for. It goes to an A/C relay.

Yes, know I could cut my harness open to follow the wires, but there has to be a better way.

Does anybody out there have a LS-5 from 72 that has a dark blue wire on the heat sensor in the passenger side? Better yet, does anybody have a wire that one end originates on the heat sensor in the head and runs to the TCS switch on the intake manifold that can see how that wire was run? s it straight from the harness? Is it a jumper?

Any input would be a huge help at this point.

Monte

added the picture to see if anybody knows if there is a plug inside the main harness right there. It also looks like there is a hoop, or wire going from one side of the connector to the other side. Again, any ideas? Sorry about the blue writing on photo.
Top is where dark blue wire went back into main harness from TCS switch.

Is that second area a plug? Any ideas?

Third area looks like there is a hoop or small wire hooping from one terminal to the other under the tape on what I think might be a plug.

Fourth and bottom area on photo. The dark blue wire should be in the main harness at the point at the bottom of the green tape. The wire is not in there at all. I opened it up to look. This is what got me looking at the areas just above it to see if there is anything out of the ordinary there. This missing wire should just keep going down to the heat sensor in the passenger side heat, but the wire is missing.

Again, any idea?

[Terry M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

I am working on a 1972, LS-5. I am trying to find the wire that goes from the TCS switch to the heat sensor on the passengers head.

Typically on a small block, there is a connector that the "TCS jumper" plugs into and from there the other end goes to the heat sensor in the passenger head.

I guess, if I understood correct, there was a question if the big blocks ever had an extra wire as a jumper. It came right out of the harness and plugged right into the heat sensor in the passenger side head.Can anyone confirm this? From what I understand, it was never resolved if any of them went straight to the sensor in the head.

My personal issue is: From the main wiring harness, there is a smaller harness that comes off and plugs into the TCS switch on the intake manifold.

The tan wire in one side of the plug has another tan wire coming off the plug going to the fast idle solenoid, as it should.
The blue wire one the other side of the plug has another wire coming off of it too. That wire goes back into the main harness, AND SHOULD GO OVER TO THE HEAT SENSOR IN THE SIDE OF THE PASSENGERS HEAD, BUT IT DOES NOT. I have gone as far as unplugging everything on the main harness on the passenger side of the distributor cap. I have that whole part of the main harness loose enough to see there is not a cut wire or something like that.

This is the rough part. This is a low mileage car that has every harness still in tact and everything on the car work the way it should. Except the TCS system due to this missing wire.

Anyway, the blue wire comes off the TCS switch and goes back into the main harness. Although a dark blue wire does continue to go in the main harness in the direction of the passenger side, it is not the dark blue wire am looking for. It goes to an A/C relay.

Yes, know I could cut my harness open to follow the wires, but there has to be a better way.

Does anybody out there have a LS-5 from 72 that has a dark blue wire on the heat sensor in the passenger side? Better yet, does anybody have a wire that one end originates on the heat sensor in the head and runs to the TCS switch on the intake manifold that can see how that wire was run? s it straight from the harness? Is it a jumper?

Any input would be a huge help at this point.

Monte

added the picture to see if anybody knows if there is a plug inside the main harness right there. It also looks like there is a hoop, or wire going from one side of the connector to the other side. Again, any ideas? Sorry about the blue writing on photo.
Top is where dark blue wire went back into main harness from TCS switch.

Is that second area a plug? Any ideas?

Third area looks like there is a hoop or small wire hooping from one terminal to the other under the tape on what I think might be a plug.

Fourth and bottom area on photo. The dark blue wire should be in the main harness at the point at the bottom of the green tape. The wire is not in there at all. I opened it up to look. This is what got me looking at the areas just above it to see if there is anything out of the ordinary there. This missing wire should just keep going down to the heat sensor in the passenger side heat, but the wire is missing.

Again, any idea?

[ATTACH=CONFIG]46274[/ATTACH]

After thinking about this some based on your earlier post on the other TCS thread -- from the AIM I seem to recall a jumper under the dash for big blocks that jumpers where a time delay switch would go for small motors. Any chance this jumper was moved from the interior to the wire harness at some point in 1972 MY? I don't think we can get to the time delay or the under dash jumper with the car assembled, so judging this is out of the question. The end result is we know less than we might if it was a judged item.

BTW: I have never seen a Corvette (or other GM car from 1970-72) with other than a green colored wire to the temperature sensor on the passenger head.

There are errors in the wiring diagram Chevrolet printed in the chassis Service Manual as well as that in the AIM. At one time there was an individual selling laminated colored wiring diagrams for each year Corvette with corrections for GM errors. I am not sure of the details, but there was a business dispute with Dr Rebuild and last time I heard the Doctor had the only colored laminated diagrams available. Monte, It might be worth your time and $ to get one, in spite of everything that goes with an attempt to purchase from that source.

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

BTW: I have never seen a Corvette (or other GM car from 1970-72) with other than a green colored wire to the temperature sensor on the passenger head.

Terry,
After looking at the AIM on page "12,A-9", it shows the basic TCS wiring. The other style jumper is on "LS-5, A-10", but does no good. The fact that you have never seen any other color than a green wire going to the heat sensor tells me everything, big blocks and small blocks, are in deed using a jumper. On all the cars I have pictures of and my car have a dark blue wire heading in the direction from the TCS switch on the manifold to the heat sensor on the head. So does all three of the wiring diagrams I have.

The wiring diagrams show a dark blue wire with a green extension. If any of them were wired directly out of the harness, it would have been a dark blue wire. It looks likethis resolves your old question of some of them maybe being wired directly.

I hate to say it, but at this point it would be very simple to resolve this situation/question. I guess it is time to open up a small part of my main harness to see exactly where that dark blue wire goes. Also, it will give me the opportunity to see if there is actually a connector and wire hoop just behind the distributor where I pointed it out in the picture.

Thanks a lot for the help. I will let you know what I find when I cut the harness open. Before I cut the harness open, I am going to check under the car to see if it by chance ended up in the starter harness and ended up coming up from the bottom of the car.

Once again, Thank you for you help.

Monte

[Patrick H.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Monte,

I have the Doc Rebuild diagram right in front of me. The blue wire goes from a staggered connector at the TCS relay on the firewall to the solenoid mounted on the intake. There should be a dark green wire from the same TCS relay to a connector which then connects to the jumper wire we've been showing/discussing. This is the connector that you think "might" be wrapped. Thirdly, there is a light green wire from the firewall TCS relay to the other TCS relay which actually has 2 different connectors, a T shaped one plus a single one with the lt green wire.

I would not cut a thing on the car until you investigate more. I find that this type of decision usually comes back to bite you right after you've made the cut.

Besides, the car may run better without it, so there is no hurry at all.

Patrick

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Patrick,
What you are explaining does not exist on my car. What I think you might be looking at the the TCS relay on the inside of the car that has a jumper across the terminal ends.
All I know about this is in the AIM on page "LS-5, A-10", it shows a relay on the inside of the car by at the "instrument panel harness assembly." So, if I put all this together, the green wire we are used to seeing terminating at the heat sensor on the passenger head heat sensor, that wire starts at the TSC switch on page "LS-5, a-10" of the AIM, and that relay is inside the car at the "instrument panel harness assembly"

So, I need to locate the TCS switch on the instrument panel harness and see if my missing green wire is hiding there.

Patrick, between the information you just relayed to me, and us talking about the inside relay earlier today, I think this has all come together.

Terry, this may help clear up the issue we were discussing about the two types of hook ups. This would make the big block and small block main harness a little different, or it was something they could change at the line.

I will let you know what I find.

Monte

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

After looking at everything again, there is no TCS relay/switch on page "LS-5,A-10". After looking at the AIM, it looks like a connector plug end with a jumper wire is in it. Just like I think is wrapped up in my harness.

Patrick, are you sure you are looking at a 1972 wiring harness? There is no other relay/switch on my firewall at all. It is very easy to see the whole thing, and I know there is no wire there.

This is very easy to resolve: I can take the plug that plugs into the TCS switch on the intake manifold, pull the dark blue wires out of the plug, remove the wire that heads back into the harness that I cannot find. Get another dark blue wire and put the wire and put the new blue wire onto the original connector and put it back into the plug. I can run that dark blue wire into the main harness and have it come out behind the passenger side head. Get a jumper like we all have been looking at over tha past day or two. Plug the jumper into my new blue wire one one end and take the other end of the jumper and plug it into the heat sensor on the passenger side head.

Now that I have done this, I have to figure out a way to make the TSC look correct, but not work because the car runs better without it hooked up. LOL

It is a non-issue any longer. It is simple to make it look correct. I do not want it working anyway.

Maybe sometime someone will have an old big block harness we can open up.

Thanks for all the help guys.

Monte

[Terry M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

After thinking about this some based on your earlier post on the other TCS thread -- from the AIM I seem to recall a jumper under the dash for big blocks that jumpers where a time delay switch would go for small motors. Any chance this jumper was moved from the interior to the wire harness at some point in 1972 MY? I don't think we can get to the time delay or the under dash jumper with the car assembled, so judging this is out of the question. The end result is we know less than we might if it was a judged item.

BTW: I have never seen a Corvette (or other GM car from 1970-72) with other than a green colored wire to the temperature sensor on the passenger head.

There are errors in the wiring diagram Chevrolet printed in the chassis Service Manual as well as that in the AIM. At one time there was an individual selling laminated colored wiring diagrams for each year Corvette with corrections for GM errors. I am not sure of the details, but there was a business dispute with Dr Rebuild and last time I heard the Doctor had the only colored laminated diagrams available. Monte, It might be worth your time and $ to get one, in spite of everything that goes with an attempt to purchase from that source.

I received an email from Geoffrey Coenen, AKA Dr Rebuild, expressing the belief that I had miss-stated the facts regarding Corvette colored laminated wiring diagrams. He stated that there are many sources for colored wiring diagrams of Corvette. With regard to his issue(s) with one other vendor he offered this link to his (Geoffrey's) web site. http://docrebuild.com/curr-evnt/currentevents-101.html as his (Geoffrey's) point of view.

I am a firm believer in the theory that there are always at least two sides to every story. In the interests of pursuing the facts I am offering one of those sides. I thanked Geoffrey for sharing with me (now us) his point of view.

[Bill C.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

monte --

from what I remember, there is not a time delay solenoid on 454 cars. they installed a jumper bridge in the harness connector.
It is located right next to the speedometer and center gauge cluster. If memory serves me correctly, the plastic connector is yellow in color.. could be wrong with this...


also -
TCS is a ground activated system (99% sure LOL).
The lead with the blue and brown wire on the TCS solenoid is always hot - has to be to keep the idle solenoid on the carburetor energized.
When you put the car in 4th gear or when the water temperature is cold or near over heat, the ground circuit is completed.

If you want it to look right and stay open full-time - full vacuum advance - then just splice a full time ground into the single wire at the TCS solenoid.

As for the green wire that connects to the Thermo switch in the PASS head -
I am pretty sure it connects into a black wire that exits the engine harness right by the wiper door actuator.

If I have stated anything incorrectly - someone will likely chime in and fix my mistake.

Bill

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Terry,

EDIT: Sorry the posts landed the way they did. I did not realize Bill Was posting at the same time, then I missed clicking on your post for continuing. It flipped the location of the posts.

I am not sure what the exercise with DR Rebuilt was. That wiring diagram does not apply to Corvette, as it says, but the wiring diagram is similar. It is similar in that it has all the same components the big block 72 seems to have. Even though they have the same components, they are in very different locations.

Over the past few days I have gone to actually looks at a few 72, LS-5 cars that are semi local. Before I left I went through the three of four different wiring diagrams I have for 1972 Corvettes.The Haynes diagram is actually pretty good and seems to be what I am finding in my car, but the other cars were a help in confirming what I think I know. I would feel better if I can find a few cars that are a little less molested or have not been restored to what the owners were told what was correct.

In looking at the other big block cars I have noticed that the typical location for the single female plug that the "TCS jumper" plugs into and runs down to the heat sensor on the passengers side head are all similar. At this point, without taking my harness apart, it looks like the single female somehow got wrapped up inside my harness. I am assuming it (the TCS solenoid) has never worked. or the other option might be that someone may have taken the time to unwrap the harness that far back and re-wrapped it. Speculation.

It does appear that the big block cars are different than the small engine cars. But, in visual appearance only, you cannot tell. At this point I would like to look at a few other 72, LS-5 cars and see if they can clear up any questions I still have floating around in my head on the matter.

There is an NCRS meet in Tahoe next month. I was plan on going, to learn more about judging anyway. While I am there, with any luck, I will find a few 72, LS-5 cars I might be able to look at.

I will let you know what I find.

At this point, for my car, I am going to plug in an aged green wire I have pulled off an old harness, make the jumper ends and plug it into the heat sensor, then take the other end and tuck it into my harness where it should be. As far as it not working,that is a simple fix at judging time. I will have another harness made up that will plug into the TSC solieoid on one end and the heat sensor on the other. It will have the appropriate plugs, connectors, and two different color wires. I will have to remove one wire that is in the TCS solenoid now, but I can tuck it away out of sight. The only drawback will be that when this new wire is running along the main harness, it will be on the outside.

A pretty simple fix. Or, I may just not worry about it and not change it at all.

I do appreciate the time you have taken to help on this matter.

Take Care,

Monte

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Bill,

This is what I have found. I do not think there ever was a question on the components. The time delay on the inside of the car is non existent. You are correct there.
The question started with my car not having the single female plug that is typically found just behind the passengers side head. It turns out after all this that it was just taped into the main harness.

I know there was some question on if the big blocks and small blocks were indeed different. I think we have finally resolve this issue as well. Yes, they are different. But, it is nothing that can be seen with opening thing up. For for judging, it is a non-issue.

I feel at this point we are done with this matter until I unwrap my harness, if I ever do. The only reason that is an issue at all is, if I look at it an determine it has or has not ever been unwrapped before.

Terry gave me enough good information earlier so I knew what to look for. It made it much easier to resolve the matter finally.

Thanks for the input, Bill.

Terry, Again, I appreciate you sticking with me on this. your original question has been resolved as well, it appears. The difference in the two. I think you may have suspected this anyway, but I hope now it s a none issue.

Monte

[Terry M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Bill,

This is what I have found. I do not think there ever was a question on the components. The time delay on the inside of the car is non existent. You are correct there.
The question started with my car not having the single female plug that is typically found just behind the passengers side head. It turns out after all this that it was just taped into the main harness.

I know there was some question on if the big blocks and small blocks were indeed different. I think we have finally resolve this issue as well. Yes, they are different. But, it is nothing that can be seen with opening thing up. For for judging, it is a non-issue.

I feel at this point we are done with this matter until I unwrap my harness, if I ever do. The only reason that is an issue at all is, if I look at it an determine it has or has not ever been unwrapped before.

Terry gave me enough good information earlier so I knew what to look for. It made it much easier to resolve the matter finally.

Thanks for the input, Bill.

Terry, Again, I appreciate you sticking with me on this. your original question has been resolved as well, it appears. The difference in the two. I think you may have suspected this anyway, but I hope now it s a none issue.

Monte

We let it go for lack of information. We made the right decision, but for the wrong reason. Thanks for your persistence.

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

I have one of the wires marked wrong. will redraw it and get it back up.
Sorry, Bill

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Sorry guys,
I will try it again.

[Monte M.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

Maybe this explains it a little betterEDIT; NEW DRAWING UPDATED.

[William C.]

Re: 1972 LS-5 Wire from TCS Switch on Intake Manifold to Heat Sensor on Head

If you still have questions on this (I'm a little late to this party,) Look at your AIM and send me the part numbers for the wiring harnesses. I may have the prints. I sent my '72 AIM off along with the car a few years back...but kept the wiring prints I had accumulated, not sure I have all of them, but worth a look if you still have questions....