98 V70 Cold Start Problem Solved

[sleddriver]

UPDATE:

Well the ECT code is back! The ECU does characterize the signal as "intermittent" and "too high".

I spoke with my indy about this and he said he went through FOUR on one car, even OEM, before he got a good one. One was even dead out of the box. Said they're just ([email protected] the OEM ones, which this one was.

As this is the ONLY engine/coolant temp sensor for this car, lots depends on it. If it's thinking my hot car is cold, no wonder it hasn't been acting right: Cooling fan running with key off, upon cold start RPM shoot to 2000 before dropping, surging,

Geesh, the first one lasted nearly 19 yrs!! Now the replacement has failed in a few months??? WTH??

 

[sleddriver]

Turns out that the sensor appears fine. It's the corroded, untinned, stranded copper wiring harness that's at fault.

I hooked up an Autodiagnos Volvo scanner, read an appropriate coolant temp reading, then tapped on the connector. The RPMs shot up, the cooling fan came on and the ECT reading dropped from 98 to -74°C when the CEL was set.

An open connection corresponds to deep cold while a shorted connection results in the highest temp reading possible.

So I'm going to rework the female end and solder in new tinned, stranded Teflon-insulated wire. That should hold up to the heat!