About a year ago, I did a clutch replacement on '92 SL, and it went great. She drives great now. Only issue is that during the install, we rushed putting things back together, and amidst the process, something went wrong with my wiring harness around the area of the Coolant Temperature sensors. When we put everything back together, cold starting the car showed that the car would crank for a long time before starting up with a rough idle before eventually smoothing out. After some time, the Check Engine light came on. My coolant temperature gauge was also stuck reading past H, and when powered off and the key removed, it would drop back down to C.
I let the car sit in my garage for some time as I was busy with my personal life but as of recent, I've begun to take care of her and bring her back to a drivable condition. Using an LED bulbs and leads, I was able to conclude that the Check Engine light is for code 21, which correlates to the Engine Coolant Temperature Sensor. Inspecting around the sensors, I noticed that there is an extremely harsh bend around the connector for the sensor, and there is a great amount of tension on said bend and no amount of tugging on the connector causes it to release.
As seen in the photo below, the wire going to the sensors are at an extremely harsh bend,
![Image]()
and here is a photo of my gauge.
![Image]()
I can conclude that the engine is not actually overheating, as I've put about 150 miles on it since the sensor issue and it's never gotten warm past any concern. The cooling system is working flawlessly. Besides, the sensor is either C or H, there is no in between, and mind you, the sensors worked flawlessly before, so that is why I am concerned it is the harness and not the sensors (Although, I should probably consider replacing the sensors, haha).
I was considering replacing the OEM sensors and gauge altogether, and I bought a ProSport gauge, but I can't find the proper NPT to BSPT adapter required. The ones I have found are the proper threads, but the center hole isn't big enough for the sensor that ProSport provides.
So I'm back to trying to fix the original gauge. Installing a new gauge won't fix my CEL and cold start issues anyways. My gauge doesn't work, the CEL is on, but my AirCon blows warm, and the temperature control works. Asked one of my friends, and he said that we may have torqued the transmission down with part of the harness in between it, but personally, this doesn't seem very likely, although it is possible I'm wrong. What advice do you guys have on this? Thanks in advance.
I let the car sit in my garage for some time as I was busy with my personal life but as of recent, I've begun to take care of her and bring her back to a drivable condition. Using an LED bulbs and leads, I was able to conclude that the Check Engine light is for code 21, which correlates to the Engine Coolant Temperature Sensor. Inspecting around the sensors, I noticed that there is an extremely harsh bend around the connector for the sensor, and there is a great amount of tension on said bend and no amount of tugging on the connector causes it to release.
As seen in the photo below, the wire going to the sensors are at an extremely harsh bend,
and here is a photo of my gauge.
I can conclude that the engine is not actually overheating, as I've put about 150 miles on it since the sensor issue and it's never gotten warm past any concern. The cooling system is working flawlessly. Besides, the sensor is either C or H, there is no in between, and mind you, the sensors worked flawlessly before, so that is why I am concerned it is the harness and not the sensors (Although, I should probably consider replacing the sensors, haha).
I was considering replacing the OEM sensors and gauge altogether, and I bought a ProSport gauge, but I can't find the proper NPT to BSPT adapter required. The ones I have found are the proper threads, but the center hole isn't big enough for the sensor that ProSport provides.
So I'm back to trying to fix the original gauge. Installing a new gauge won't fix my CEL and cold start issues anyways. My gauge doesn't work, the CEL is on, but my AirCon blows warm, and the temperature control works. Asked one of my friends, and he said that we may have torqued the transmission down with part of the harness in between it, but personally, this doesn't seem very likely, although it is possible I'm wrong. What advice do you guys have on this? Thanks in advance.
