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
  • MECHANIC
  • 52,797 POSTS
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
Images (Click to make bigger)
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
+1
Thursday, June 13th, 2019 AT 6:34 AM
Tiny
PREFERTODIY
  • MEMBER
  • 5 POSTS
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?
Was this
answer
helpful?
Yes
No
Thursday, June 13th, 2019 AT 6:48 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
Was this
answer
helpful?
Yes
No
+1
Thursday, June 13th, 2019 AT 6:53 AM
Tiny
PREFERTODIY
  • MEMBER
  • 5 POSTS
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?
Was this
answer
helpful?
Yes
No
Thursday, June 13th, 2019 AT 7:00 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Does the AC system work?

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

Roy
Was this
answer
helpful?
Yes
No
Thursday, June 13th, 2019 AT 7:07 AM
Tiny
PREFERTODIY
  • MEMBER
  • 5 POSTS
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.
Was this
answer
helpful?
Yes
No
Thursday, June 13th, 2019 AT 7:10 AM
Tiny
PREFERTODIY
  • MEMBER
  • 5 POSTS
Am I correct in the photo as to that being the temperature sensor?
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Thursday, June 13th, 2019 AT 7:15 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
That is correct.

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

Roy
Was this
answer
helpful?
Yes
No
+1
Thursday, June 13th, 2019 AT 7:17 AM

Please login or register to post a reply.

Related Engine Overheat Content

Is Your Engine Cool Enough to Check?
VIDEO
Is Your Engine Cool Enough to Check?
In­struc­tional re­pair video
Overheating Symptoms
GUIDE
Overheating Symptoms
An over­heat­ing en­gine is never a good thing to have hap­pen. If the prob­lem is caught quickly you can save the headache of a ma­jor en­gine re­pair. Know­ing the in­for­ma­tion from...
VIEW MORE