Cooling fan won't come one

[oldshoman]

Okay...I've read a lot of posts about a non functioning cooling fan. Here is my story.
changed CCRM
changed temperature sensor
KOEO test...fan turns on
Turn on AC on high..fan does not turn on....neither does the AC
If I disconnect the temperature sensor, the fan comes on (so does the check engine light)

At this point, at least for a temporary fix, i ordered a Flex-a-lite 31147 Adjustable Temperature Control Unit to by pass the ECC temp controls
http://www.amazon.com/gp/product/B00029J3ZW/ref=oss_product

I am not sure if the nonworking AC is part of this problem.
Any feedback or suggestions for further testing would be appreciated.

 

[rubydist]

is the a/c charged?

 

[Phoenix]

The AC and the fan goes through the CCRM , maybe the CCRM is made in a way that if the AC dont engage , fan wont come on.

 

[oldshoman]

Independant of the AC not working, the fan doesn't come on to cool the engine.

 

[luigisho]

Bad temp sensor? Replacing that (along with the water pump belt and temp. switch) cured the same problem on my GenIII yesterday (and helped the a/c stay engaged).

 

[rubydist]

The AC and the fan goes through the CCRM , maybe the CCRM is made in a way that if the AC dont engage , fan wont come on.

That is correct, which is why I asked if the a/c was charged. if the a/c doesn't kick on, the pcm won't tell the cooling fan to come on with the a/c.

If the cooling fan won't kick on normally, but does when the koeo test is run, that suggests that the engine temp sensor never tells the pcm that the engine is warm. This can occur accurately, if the thermostat is always open such that the engine never warms up, or inaccurately if the temp sensor is bad. The temp sensor that tells the pcm this information is the one on the rear side of the thermostat housing, the one w/ 2 terminals. (The other temp sensor with just one terminal is only for the gauge.)

 

[oldshoman]

That is correct, which is why I asked if the a/c was charged. if the a/c doesn't kick on, the pcm won't tell the cooling fan to come on with the a/c.

If the cooling fan won't kick on normally, but does when the koeo test is run, that suggests that the engine temp sensor never tells the pcm that the engine is warm. This can occur accurately, if the thermostat is always open such that the engine never warms up, or inaccurately if the temp sensor is bad. The temp sensor that tells the pcm this information is the one on the rear side of the thermostat housing, the one w/ 2 terminals. (The other temp sensor with just one terminal is only for the gauge.)

As I first posted. I replaced the temp sensor and the ccrm already. Does anyone know the readings from the temp sensor so I can test it in hot water?

 

[rubydist]

Is the engine properly grounded? (i.e. is there a good ground strap between the intake and the firewall?) I just experienced this on my white 94 - without that ground strap in my case the engine would run (in many cases the engine will not even run w/o this ground strap), but the coolant temp gauge was not reading properly, and the cooling fans would not come on until the coolant temp was way high.

 

[firebat45]

IIRC it's supposed to turn on at 192 F.

 

[yamahaSHO]

Which temp sensor did you replace?

 

[SHOtime2511]

yup,there are two.

 

[oldshoman]

Which temp sensor did you replace?

I replaced the two wire ETC sensor. I think the other sensor is for the gauge.

 

[oldshoman]

Is the engine properly grounded? (i.e. is there a good ground strap between the intake and the firewall?) I just experienced this on my white 94 - without that ground strap in my case the engine would run (in many cases the engine will not even run w/o this ground strap), but the coolant temp gauge was not reading properly, and the cooling fans would not come on until the coolant temp was way high.

There are grounds on both firewalls. They were pretty messy, and I cleaned them both. Thanks! It didn't cure the fan problem but the hood light now works!!

 

[rubydist]

Then I expect you either have a wiring problem between the temp sensor and the pcm, or you have a pcm problem. do you have someone that you could swap pcm's with as a test?

 

[oldshoman]

Then I expect you either have a wiring problem between the temp sensor and the pcm, or you have a pcm problem. do you have someone that you could swap pcm's with as a test?

I have tried 2 pcms and the same thing happens. This is strange because the temp sensor if I remember varies between .4 and approx 4 volts at the higher temp. When I disconnect the lead from the ECT, the fan comes on, so...follow my reasoning...the lack of any signal turns on the fans. Also,when I disconnect, the temp sensor lead, the check engine light turns on.

 

[rubydist]

That suggests that you have either a bad connector or a bad wire somewhere between the temp sensor and the pcm.

 

[oldshoman]

That suggests that you have either a bad connector or a bad wire somewhere between the temp sensor and the pcm.

Time to pull out the voltmeter and the wiring diagram...

 

[luigisho]

Time to pull out the voltmeter and the wiring diagram...

Unfortunately that might be correct. The only other explanation would be a faulty new sensor??