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91 Coolant Temp Gauge Pegged Below Cold

Old 07-16-2018, 06:45 AM
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Default 91 Coolant Temp Gauge Pegged Below Cold

Hey guys, I've got a doozey here and before I just replace every part to do with the coolant temp, I wanted to ask around hoping someone has dealt with this.

So I had my dash out to replace the brake booster and brake master, and after I buttoned everything back up, I noticed the coolant gauge looked like it had fallen well below where it usually sits. It's currently about at the left screw below the cold side. It looks like this but further left and doesn't ever move:
91 Coolant Temp Gauge Pegged Below Cold-maxresdefault.jpg

So I immedately assmed that the 902-870 from Moss was the part I needed and assumed that it went here:
91 Coolant Temp Gauge Pegged Below Cold-p2.jpg

But after some digging I found this picture:
91 Coolant Temp Gauge Pegged Below Cold-ecu_sensor_2.jpg

The Computer sensor is the 902-871 and the dashboard gauge sensor appears to be 902-870. So I ordered 902-871 and a new thermostat and plan to put them all in. But I'm confused about one thing. When connecting the instrument cluster, I attached the left and right connector, the speedo, but I couldn't find the tiny two-wire connector. After about three hours of looking, reading through service manuals, and googling, I pulled it back out and took the cluster apart and found that those wires just went to the defrost light and the small board attached to it. I don't have a hard top and don't care about defrost so I left it unplugged rather than pulling my whole dash again two find this seemingly unimportant connector. (I seriously laid under my steering column for hours looking. It's simply not visible. It's probably tucked away somewhere I can't see)

Is there some chance that this connector puts anything towards the coolant temp gauge? I was having a weird idle issue before doing this and it seems like the stars are aligning and the ECU and dash coolant sensors finally failed but because there is something that I obviously changed, despite how improbable it seems, basic troubleshooting tells me that the defrost cable has to be the issue.

I've ordered the parts and will be replacing them regardless. I'm just halfway through a nightshift and I'm anxious about it.
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