Overheating

Tiny
PREFERTODIY
  • MEMBER
  • 2000 MERCURY VILLAGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
This van is overheating. The radiator fans do not engage even when the AC is turned on max. We have checked the relays, fuses, wiring harnesses, and all test as working. The temp sensor also tested as good. When we unplug the temp sensor the fans engage and run on what sounds like high speed. We did not find any cracks or leaks in any hoses. We have it pulled up on ramps and have let it run and have not seen any leaking. It is not throwing any codes either. I'm not entirely sure that it got to temperature at idle as the OMBII reader showed it at 197 degrees. Someone mentioned that there might be a temperature sensor/switch as well as a sensor but we are not able to locate one.
Thursday, June 13th, 2019 AT 5:32 AM

8 Replies

Tiny
ASEMASTER6371
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Good morning,

What sensor did you disconnect that made the fans run?

https://www.2carpros.com/articles/engine-overheating-or-running-hot

By disconnecting the coolant sensor and the fans coming on, that confirms the circuit is working correctly. This indicates the sensor is faulty and not send the correct signal to the PCM.

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

Roy
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Thursday, June 13th, 2019 AT 6:34 AM
Tiny
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We disconnected the sensor shown in the first photo. It shows voltage on a meter when checked. Are you saying that when it is disconnected and the fans start that the sensor is bad? My husband felt that doing so indicates the sensor is working because it went into fail-safe mode and threw a code. Fans stop when sensor reconnected. We are almost to the point of thinking the PCM is what is bad. Is there a way to check the PCM? Where is it located?
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Thursday, June 13th, 2019 AT 6:48 AM
Tiny
ASEMASTER6371
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The sensor measures temperature and sends a signal to the PCM. When you disconnect it, it sends a high temperature signal to the PCM and commands the fans on.
When you jump the 2 pins, it sends a cold temperature reading to the PCM.

Yes, the sensor is bad.

Roy
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Thursday, June 13th, 2019 AT 6:53 AM
Tiny
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And this applies to the fan not engaging when the AC is turned on max? Shouldn't the fans come on at that point no matter the temperature sensor reading?
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Thursday, June 13th, 2019 AT 7:00 AM
Tiny
ASEMASTER6371
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Does the AC system work?

The high side of the AC has to be at 150 lbs for the fans to engage.

Roy
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Thursday, June 13th, 2019 AT 7:07 AM
Tiny
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AC does not blow cold. Fan blower works. We are pretty sure the compressor is working. We attempted to add Freon with ACPro type product but that gauge did not show any charge at all.
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Thursday, June 13th, 2019 AT 7:10 AM
Tiny
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Am I correct in the photo as to that being the temperature sensor?
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Thursday, June 13th, 2019 AT 7:15 AM
Tiny
ASEMASTER6371
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That is correct.

The AC must work before it will turn on the fans.

Roy
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Thursday, June 13th, 2019 AT 7:17 AM

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