Coolant temp senser - Team Camaro Tech
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post #1 of 18 (permalink) Old Sep 1st, 14, 07:58 AM Thread Starter
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George
 
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Coolant temp senser

On my 67 rs 327 I have a light and no gauges. Many moons ago the green wire got cut off and I have not had a temp light. I tested the circuit by grounding the green wire and my light lights up. But it does not light up as a test when you turn the key to the almost starter engaging position. I can hear a relay click, all the other lights get a bit brighter but the temp gauge does not light. Is this because there is no sender on the engine? I thought that the sender for a light was a simple on off switch and that not having one would make no difference for the test. Is it not that simple? Also, I could swear that the original sensor was the kind with the nail head terminal that the black pigtail slid over from the side. But all of the sensors that I can find for a light are a spade terminal. The nailhead ones are all gauges only. Is this right? Am I remembering incorrectly? Can anyone with just a light check to see what kind of pigtail they have on their coolant temp sensor? Also where do I get that cloth wire cover for the green wire as it passes over the valve cover edge. Mine has disintegrated. I dont want to use plastic. Edit: Is this the right stuff?

http://www.homeprofasteners.com/inde...product_id=420
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post #2 of 18 (permalink) Old Sep 1st, 14, 08:19 AM
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Re: Coolant temp senser

Yes it will not self test if it can't ground I believe. Lectric Limited sells repair leads and should be able to get you a unit to fit your current sender. http://www.lectriclimited.com/mainpage.htm

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TEMPERATURE SENDING UNIT LEAD REPAIR KIT

Various Temperature Sending Unit Repair Kits
Over the years, because of the lack of accurate replacement temperature sending units, car owners and mechanics were forced to improvise. After finding a sending unit that adequately worked, they would cut-off the original terminal & connector from their harness and splice on one that mated to their new sending unit. With this kit, you can repair your temperature sending unit lead wire and get it back to the way it originally looked and functioned.
Kits includes new asphalt loom, wire, terminal and connector and are pre-assembled.

We offer many different Temperature Sending Unit Lead Repair Kits.
View Catalog / Order Online


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post #3 of 18 (permalink) Old Sep 1st, 14, 09:18 AM
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Re: Coolant temp senser

Classic has this wiring set that has everything but the sending unit.

Roger

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post #4 of 18 (permalink) Old Sep 1st, 14, 09:50 AM
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Re: Coolant temp senser

I have no idea if 67 and or 68 are the same, but 69 without gauges (light only) used a small pin type connector, not the nail head and not the spade.

Again, the pics that follow are 69 assembly line correct.
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post #5 of 18 (permalink) Old Sep 1st, 14, 10:24 AM Thread Starter
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Re: Coolant temp senser

Thanks for the pics and the links. That seems to be just what I need. My sensor is not in the head but I actually have the pigtail for that type of sensor laying around. Ill have to see what the local "old school" auto parts place has. Now as far as the self test goes. Shouldnt the bulb self test work even without a sensor when I crank the motor. Doesnt the ignition switch ground that wire during cranking. The sensor is an open circuit anyway when cold, right? I know the circuit is good as I can light the light by grounding the green wire under the hood. Or maybe the cold sensor is not completely open and the self test needs to see this resistance to work?
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post #6 of 18 (permalink) Old Sep 1st, 14, 10:29 AM
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Re: Coolant temp senser

I believe the 67, 327 is like the 350 and located in the intake. This is a picture of my sending unit I know to be stock.

Roger
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post #7 of 18 (permalink) Old Sep 1st, 14, 12:13 PM Thread Starter
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Re: Coolant temp senser

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Originally Posted by rogerh View Post
I believe the 67, 327 is like the 350 and located in the intake. This is a picture of my sending unit I know to be stock.

Roger
Thats just what I needed. Its the one with the pin. I have that pigtail. Thanks.
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post #8 of 18 (permalink) Old Sep 1st, 14, 12:23 PM
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Re: Coolant temp senser

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Originally Posted by carbuff67rs View Post
Shouldnt the bulb self test work even without a sensor when I crank the motor. Doesnt the ignition switch ground that wire during cranking.
I'm not sure without my documents but I think the ignition powers the bulb for the self-check. Is the bulb there good?


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post #9 of 18 (permalink) Old Sep 1st, 14, 02:50 PM
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Re: Coolant temp senser

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Originally Posted by carbuff67rs View Post
Thats just what I needed. Its the one with the pin. I have that pigtail. Thanks.
That's great, glad I could help.

Roger

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post #10 of 18 (permalink) Old Sep 1st, 14, 03:30 PM Thread Starter
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Re: Coolant temp senser

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Originally Posted by 69-Pace View Post
I'm not sure without my documents but I think the ignition powers the bulb for the self-check. Is the bulb there good?
Yes, bulb is good as I can make it come on by grounding the green sensor wire in the engine compartment.
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post #11 of 18 (permalink) Old Sep 1st, 14, 03:33 PM
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Re: Coolant temp senser

ground the wire and move to the run key position and see if the self check then initializes the bulb circuit.


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post #12 of 18 (permalink) Old Sep 1st, 14, 03:59 PM Thread Starter
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Re: Coolant temp senser

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Originally Posted by 69-Pace View Post
ground the wire and move to the run key position and see if the self check then initializes the bulb circuit.
Yes, if I ground the wire and put it in run it will stay lit all day. I believe thats the sensor circuit doing its job simulating an overheat situation. I believe that the self test applies a ground to the circuit when you put the key in the cranking position then going back to off when it goes back to run.
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post #13 of 18 (permalink) Old Sep 4th, 14, 09:23 PM Thread Starter
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Re: Coolant temp senser

Ok, so I got the correct sensor and got the wiring all squared away. There is still no self test of the temp light while cranking or in run. when I turn the key towards cranking, right before it gets to that point, I can hear a relay click in the engine compartment and the gen light gets much brighter. This is the point where I feel the temp light should light. But it does not. Does anyone know how this circuit works? On a side note it is very hard to find the correct sensor with the pin connector. They all seem to have the flat blade connection. In the box was a slide on connector with a pin soldered to it soit seems even the manufacturer knows the blade terminal is not right for this application.
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post #14 of 18 (permalink) Old Sep 5th, 14, 09:28 AM
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Re: Coolant temp senser

Quote:
Originally Posted by carbuff67rs View Post
Ok, so I got the correct sensor and got the wiring all squared away. There is still no self test of the temp light while cranking or in run. when I turn the key towards cranking, right before it gets to that point, I can hear a relay click in the engine compartment and the gen light gets much brighter. This is the point where I feel the temp light should light. But it does not. Does anyone know how this circuit works? On a side note it is very hard to find the correct sensor with the pin connector. They all seem to have the flat blade connection. In the box was a slide on connector with a pin soldered to it soit seems even the manufacturer knows the blade terminal is not right for this application.
There are 2 - #20 dark green wires running to the same connection on the dash "temp" light. The obvious one comes from the temp sensor in the block through the bulkhead connector. The second goes to the ignition switch, then, through the bulkhead connector to the horn/key buzzer relay. The "temp" bulb on the dash should light when the switch is in the "start" position as this uses the switch/horn relay circuit as your "test" circuit. The click you are hearing is mostly likely the horn relay clicking in. Make sure all wires and connections are in good condition to make this part of the circuit functional. Do the horns work properly?

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post #15 of 18 (permalink) Old Sep 5th, 14, 10:19 AM
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Re: Coolant temp senser

Difference in sensors (T-head vs. the Pin or Spade connector) is that a gauge sensor has a gel inside of it that changes resistance with heat allowing the needle to move as temp rises and resistance drops. The other uses mercury or similar fluid to expand as it gets hot pushing on a plunger inside the sensor, against a spring, until it contacts the lip inside the sensor bore grounding the sensor to trip the light on the dash.

One is either on or off, the other offers an analog resistance to ground proportional with temperature. I imagine the gauge sensor would eventually allow the idiot light to come on but I have no ideas as to at what temp that would occur. It also costs a lot more than the more complex to make and complicated idiot light sensor, which shows you how people that have expensive toys will pay more to maintain them (both Cadillac and Chevy use the same parts, but it cost a lot more to buy the Caddy part than the same part from Chevy). This is because the Caddy owners knows that deep down inside that "Best of all it's a Cadillac" (a marketing ploy dreamed up to sell Chevy Novas to Cadillac owners at a higher price).

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