Question About 85 Coolant Sensors
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Question About 85 Coolant Sensors
My 85 has three coolant sensors. One in the driver side head, one in the pass side head and one in the front of the intake manifold. Which sensor feeds the ECM and which one feeds the display on the dash?
I'm trying some data logging using Tuner Pro RT. The coolant temp displayed by Tuner Pro is 40 degrees cooler than the dash display. My fans seem to be coming on based on the dash display.
I'm trying some data logging using Tuner Pro RT. The coolant temp displayed by Tuner Pro is 40 degrees cooler than the dash display. My fans seem to be coming on based on the dash display.
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
The two wire connector is for the computer, the passenger cylinder head is the sensor that controls the fans, and the other sensor is for the gauge, if I remember correctly. The fans, gauge and computer all have different sensors on the earlier C4's.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
The display is from the driver head, and the Tunerpro is getting that signal from the intake, maybe the intake sensor is not in the coolant stream,, just guessing
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Burning Brakes
Joined: Nov 2010
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From: Spartanburg South Carolina
Actually i think Jim got it right the second time.
Drivers side head = sensor for the aux fan.
Pass head = sensor for dash gauge.
At least that's the way it is in my 89.
The main fan is turned on by inputs from the sensor in front of the intake mani which feeds the ecm, the vehicle speed sensor, and a sensor on the A/C system
The Aux fan only(not main) is turned on by the sensor in the drivers side head.
I had to go through all the wires on mine because the previous owner of my car had wired the main fan relay to the drivers side head sensor which forced the main fan to come on regardless of what the vehicle speed sensor was saying. He road raced the car. So when that sensor hit it's designed temp it would ground the relay and energize the fan. Pretty cool really. You could buy any desired sensor temp.
Drivers side head = sensor for the aux fan.
Pass head = sensor for dash gauge.
At least that's the way it is in my 89.
The main fan is turned on by inputs from the sensor in front of the intake mani which feeds the ecm, the vehicle speed sensor, and a sensor on the A/C system
The Aux fan only(not main) is turned on by the sensor in the drivers side head.
I had to go through all the wires on mine because the previous owner of my car had wired the main fan relay to the drivers side head sensor which forced the main fan to come on regardless of what the vehicle speed sensor was saying. He road raced the car. So when that sensor hit it's designed temp it would ground the relay and energize the fan. Pretty cool really. You could buy any desired sensor temp.
Last edited by Dr.Huxtable; Feb 5, 2012 at 12:36 AM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Prior to, gauge sender was between # 1 and 3
Also in 1985 only
it had a mech switch as a over ride for the fan (controlled by the ECM ) that was not used on any other years
84 only had the mech fan switch and no ECM control of fans
Last edited by rodj; Feb 5, 2012 at 07:49 AM.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
The tuning has been an adventure. I got the Moates programmer and adapters. I had Moates install the adapter on the ECM. I copied the bin file from the original 2732 chip to a new flash chip. When I installed the flash chip the car would not start. After a lot of head scratching I started over. I again read the 2732 chip and this time got a different bin. It looks like the first copy had random changes in values including the prom ID. My wife thinks it was caused by solar flares. Wierd!
Yesterday I got the car running and I successfully logged data with Tuner Pro. That's when I found the sensor problem. Before I make any changes to the tune, I have to get all the sensors working.
Caboboy (Tim) has offered to help me with the tuning. I'll be taking advantage of his experience. I'm looking forward to getting started. I have a feeling there's still some untapped power in this motor.
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
Hopefully your new sensor will resolve your issue. I have run several scans and have the same chip mods you have. I used a stock BIN file that I have modified somewhat. My car runs good, but I would love help in deciphering the limited scan info the 870 ECM offers, and adjusting my tune. Maybe we can compare.....already we share the temp issue. My MAF readings in GPS at WOT seem to be half of what I THINK they should be. There is very little info out there on the 85 ECM.
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Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
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From: Santa Maria, CA
Hopefully your new sensor will resolve your issue. I have run several scans and have the same chip mods you have. I used a stock BIN file that I have modified somewhat. My car runs good, but I would love help in deciphering the limited scan info the 870 ECM offers, and adjusting my tune. Maybe we can compare.....already we share the temp issue. My MAF readings in GPS at WOT seem to be half of what I THINK they should be. There is very little info out there on the 85 ECM.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
I have all the Moates gear already, and have been scanning.(tunerproRT) Every time I have done a scan, I have done more mods. My only issue (and its a big one) is that my car will not rev over about 4300 RPM. I have posted my scans on here before, not much feedback. Which is fine, I am forced to learn this stuff on my own. My car runs great other than that.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
I find this interesting. I just replaced the ECM coolant sensor. I checked the sensor output with Tuner Pro RT and got a 35-40 degree lower temperature than the dash display. I know the dash display is correct. My next step is to check the sensor using WINALDL rather than Tuner Pro.
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
Mine says 163 degrees on Tunerpro fully warmed up, about 200 on the dash display. 163 seems like enough to shift the OD and put me into closed loop. But I wonder how this seemingly low temp might effect certain tables on my tune. My 4+3 OD is enabled at 147 on the display, just like it is supposed to. We have much to learn. I would like to see what your MAF flow is under load. This is another area where I think mine is showing incorrectly.
Last edited by powerpigz-51; Feb 9, 2012 at 12:58 AM.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Mine says 163 degrees on Tunerpro fully warmed up, about 200 on the dash display. 163 seems like enough to shift the OD and put me into closed loop. But I wonder how this seemingly low temp might effect certain tables on my tune. My 4+3 OD is enabled at 147 on the display, just like it is supposed to. We have much to learn. I would like to see what your MAF flow is under load. This is another area where I think mine is showing incorrectly.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
The most I get out of mine is 105 gms/s....which I think is a clue to my problem...I do believe the MAF is good and reading properly. If you look at the tables on the tune, we should see well over 200. I am not getting the air flow that I should.