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Rad fan always on hi with engine running

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cbova
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Joined: Sun Apr 28, 2019 6:33 pm
Year and Model: 2005 XC70
Location: NH
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cbova

Rad fan always on hi with engine running

Post by cbova » Sun Apr 28, 2019 6:49 pm

Recently the radiator fan started running on high as soon as the engine was started (even stone cold). It shuts off when the engine is turned off. Key on, engine off it does not run. I have no OBDII codes and my coolant temp is reading normal with my scan tool. The AC failed a few years ago (internal compressor failure) but the system was still charged. No other symptoms besides no cold air. Now diagnosing this fan issue I checked the AC charge and there is no pressure in the system anymore. I read somewhere that if there is no pressure reading at the AC pressure sensor the fan will run on hi (I guess as a fail safe for a faulty sensor). So what I'm trying to do is bypass the sensor so I know for sure that's what the issue is. Seems easy enough except it's a 3 wire sensor. I have tried just unplugging it but there was no change. What terminals need to be jumpered to signal normal pressure? Or am I barking up the wrong tree?

Thanks



cbova
Posts: 4
Joined: Sun Apr 28, 2019 6:33 pm
Year and Model: 2005 XC70
Location: NH
Has thanked: 0
Been thanked: 0
United States of America
cbova

Re: Rad fan always on hi with engine running

Post by cbova » Fri May 03, 2019 8:32 pm

I messed around a little more and decided to remove the AC pressure switch (no charge left). After I plugged it back into the harness with the switch out of the drier the fan acted 100% normal. This didn't make sense since the only change was the fact that the switch was no longer installed. I ordered a new switch from FCP and and and put that back in. So far It's acting normal. Best guess at this point was a flaky sensor that happened to clear up when I touched it to remove it. We'll see if the new sensor continues to act normal.



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