84 crossfire coolant temp switch
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
84 crossfire coolant temp switch
Ok just a few questions while Im trying to understand some things.
The coolant temperature switch in front in the manifold, controls when the system is in closed loop rather than open loop? So when the temp reaches a certain point (I would guess about the same as the thermostat temp ?) it goes into closed loop controlled by the switch closing the contacts.
So to check the switch I could run the engine until it reaches some temperature then measure across the contacts for continuity (with the connector off).
What actual temperature should it close at?
And is there any obvious way of telling while driving if the system is in open loop or closed loop?
Maybe I will need an aldl cable and a laptop. Can someone recommend a decent aldl cable for the 84 that doesnt cost $50? Is a serial one better than usb or usb better?
The coolant temperature switch in front in the manifold, controls when the system is in closed loop rather than open loop? So when the temp reaches a certain point (I would guess about the same as the thermostat temp ?) it goes into closed loop controlled by the switch closing the contacts.
So to check the switch I could run the engine until it reaches some temperature then measure across the contacts for continuity (with the connector off).
What actual temperature should it close at?
And is there any obvious way of telling while driving if the system is in open loop or closed loop?
Maybe I will need an aldl cable and a laptop. Can someone recommend a decent aldl cable for the 84 that doesnt cost $50? Is a serial one better than usb or usb better?
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
ok then what resistance should I measure at 180-190 I guess it would be to check it at. Everywhere I see calls it a switch biut if its a thermister I can do that too. Just use an ohmeter.
Racer
Joined: Aug 2013
Posts: 301
Likes: 0
If you have a laptop with a serial port, you can make a cable cheap, instructions on this site http://cable.invisibill.net/
The coolant temp sensor at the front of the intake is for the computer, and the one in the drivers side head is for the guage. I am thinking that they should both read the same resistance (or at least close) at any given temp, the one for the computer just has a dedicated ground so it is a more accurate and reliable signal. BTW, the temp "switch" is the one in the passenger side head, and it controls the cooling fan relay. Only the 84 is like this.
The coolant temp sensor at the front of the intake is for the computer, and the one in the drivers side head is for the guage. I am thinking that they should both read the same resistance (or at least close) at any given temp, the one for the computer just has a dedicated ground so it is a more accurate and reliable signal. BTW, the temp "switch" is the one in the passenger side head, and it controls the cooling fan relay. Only the 84 is like this.
Last edited by nobodycls; Dec 9, 2013 at 10:21 PM.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
ok thanks everyone niw I will just see how hard it is to get some alligator clips or some kind of test clip on the pins with the connector off.
Im only getting about 10mpg in the city and its starting to get to me I wish I could afford to drive it more lol
Im only getting about 10mpg in the city and its starting to get to me I wish I could afford to drive it more lol
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
By the way, if the thermister doesnt control going into closed loop mode what exactly does it set?
And the link above for the aldl cable, it shows pin m for data. I thought pin E was for data on the 1984?
And the link above for the aldl cable, it shows pin m for data. I thought pin E was for data on the 1984?
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Race Director
Joined: Apr 2002
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From: Anaheim CA
The CTS (Coolant Temperature Sensor) is used by the ECM to determine injector pulse width (mixture or AFR) and spark advance.
The car will not go into closed loop mode until the O2 sensor reaches operating temperature.
The ECM richens the mixture when the coolant is cold, so it might think the coolant is cold ALL the time. That will happen if the CTS has a bad connection (corroded pins) or a broken wire. The CTS itself could be bad. Here's a little CTS chart from the FSM:
The car will not go into closed loop mode until the O2 sensor reaches operating temperature.
The ECM richens the mixture when the coolant is cold, so it might think the coolant is cold ALL the time. That will happen if the CTS has a bad connection (corroded pins) or a broken wire. The CTS itself could be bad. Here's a little CTS chart from the FSM:
Team Owner
Joined: Sep 2003
Posts: 25,393
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If you have an after-market supplier change the GM/ACD part number that could also possibly give you both the sensor and the connector in "the same box"!
Last edited by WVZR-1; Dec 10, 2013 at 08:00 AM.
Racer
Joined: Aug 2013
Posts: 301
Likes: 0
I thought it was the coolant temp switch for the fan that had the knock sensor style connector.(single wire)
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
ok before we get too far off topic let me ask a few things.
One, should I use teflon tape if I do replace it or not?
Two, do I need to drain some coolant and is draining it from the radiator sufficient even if the thermostat isnt open (draining it at lower temperature)
Three, where can I find the other end of the wires from the connector so I can check at that end for resistance or for voltage? Then I would know if theres any reason to replace the connector too. Or if theres and loss of contact to complete the circuit. Where does it connect to?
One, should I use teflon tape if I do replace it or not?
Two, do I need to drain some coolant and is draining it from the radiator sufficient even if the thermostat isnt open (draining it at lower temperature)
Three, where can I find the other end of the wires from the connector so I can check at that end for resistance or for voltage? Then I would know if theres any reason to replace the connector too. Or if theres and loss of contact to complete the circuit. Where does it connect to?
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
Teflon is fine. I loosen the other bad untill I can turn it by hand have the other one ready to go as soon as you get the old one out you will losse a little cooleant depending how fast you are. The other end of the harness is at the ecm if I am understanding your question right
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
Teflon is fine. I loosen the other bad untill I can turn it by hand have the other one ready to go as soon as you get the old one out you will losse a little cooleant depending how fast you are. The other end of the harness is at the ecm if I am understanding your question right
Do you know what pins it goes to? Is it sensitive to where a dmm on ohms might harm it? And is there a connector at the ecm side? For the temp sensor.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
ok before we get too far off topic let me ask a few things.
One, should I use teflon tape if I do replace it or not?
Two, do I need to drain some coolant and is draining it from the radiator sufficient even if the thermostat isnt open (draining it at lower temperature)
Three, where can I find the other end of the wires from the connector so I can check at that end for resistance or for voltage? Then I would know if theres any reason to replace the connector too. Or if theres and loss of contact to complete the circuit. Where does it connect to?
One, should I use teflon tape if I do replace it or not?
Two, do I need to drain some coolant and is draining it from the radiator sufficient even if the thermostat isnt open (draining it at lower temperature)
Three, where can I find the other end of the wires from the connector so I can check at that end for resistance or for voltage? Then I would know if theres any reason to replace the connector too. Or if theres and loss of contact to complete the circuit. Where does it connect to?
You can drain some coolant out of the radiator with a turkey baster. If you don't happen to have one, they are really cheap at the 99 cent stores.
The CTS goes directly to the ECM. It is located under the dash on the passenger side. It is mounted in a plastic bracket bolted to the firewall inside the cabin. There are two large connectors on the ECM and everything goes to those connectors. One is two rows of 12 pins and the other is 2 rows of 16 pins. You can access the ECM by removing the passenger side kick panel (several 7mm screws) and it is held in the bracket by two 10mm bolts. After removing those bolts, it drops out of the bracket. It's the metal box sitting on the floor in this pic (the connectors are normally on the bottom):
Last edited by Cliff Harris; Dec 11, 2013 at 03:47 AM.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
Well my thinking was if the varying resistance presents a varying voltage at the ecm that would show its all connected. Otherwise Im not sure why I would want to replace the connector, just to use a different part? Are the original style ones hard to find?
Team Owner
Joined: Sep 2003
Posts: 25,393
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If you're confident that your connector is good and you could get someone to convert the original GM 25036092 to a service part with the original connector you should be good. The reliability of the newer style sensor and connector is certainly worth the effort to do. The original GM part should be very difficult to find. Very!
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,027
Likes: 30
From: Granite City Illinois
If you're confident that your connector is good and you could get someone to convert the original GM 25036092 to a service part with the original connector you should be good. The reliability of the newer style sensor and connector is certainly worth the effort to do. The original GM part should be very difficult to find. Very!
Last edited by ToniJ1960; Dec 12, 2013 at 01:40 AM.