have you checked the 2 wire gray connector on the battery neg. cable.?
Can you tell which speed the fan is running on, is it high speed or low speed?
The gray connector is the ground for the CCRM and it is bad about getting corrioded and causing a similar concern but usually you will also get a no start condition along with the cooling fan running on high.
Usually with cooling fan running on high as soon as the key is turned on would be a loss of communication to the PCM, high speed fan is the default for this.
I would recommend to first pull the gray connector apart and make sure you have no corroision present, if so just cut it out and splice the wires back together,
Take the connection loose at the PCM and clean it good with some spray electrical cleaner and dry it out good nefore reconnecting.
And last look at the self test connector good make sure none of the wires to it are grounding out maybe causing vehicle to go into self test.
ONE LAST QUESTION, WHERE IS THE PCM EXACTLY?
You may also want to check the wiring from pins 14(tan/orange) and pin 17 (light green and purple) at the CCRM to the PCM pins 13 (T/O)0 and pin 31(LG/P) . disconnect the connectors at the CCRM and PCM and ohm them out to make sure you don't have an open circuit,especially on the LG/P.
The PCM (powertrain control module) is located on the right side(passenger) of vehicle under the hood at the firewall.It will have a big regtangular connector with a 10MM bolt in the center of it.You will only be able to see the connector of it because the module itself goes inside the vehicle.
I STILL DON'T SEE THE PCM. THERE IS A UNIT NEXT TO THE WINDSHIELD WASHER FLUID CONTAINER ON THE PASSENGER SIDE THAT HAS A BIG RECTANGULAR PLUG, SOME KIND OF ELECTRICAL CONNECTION. I CLEANED THAT WITH CRC ELECTRICAL CLEANER, BUT STILL HAVE THE PROBLEM. WHAT IS THE PCM NEXT TO? CAN YOU GIVE ME A BETER DESCRIPTION? IT IS A TAURUS LX IF THAT HELPS. I JUST DON'T SEE ANYTHING WITH A 10MM BOLT. I PRINTED OUT YOUR REPLY IN ANY CASE, SO I WOULD BE ABLE TO TRY AND FIGURE OUT WHAT YOU SUGGESTED. THANKS FOR YOUR HELP
Here is a pic of it.
The round cylinder in the pic is your right strut tower
Did you check the gray 2 wire connector?
If you did then go to the PCM and on pin 31(LG/P) wire take a jumper wire and ground this wire. If this shuts the cooling fan off then the problem is either the PCM itself is bad or it is seeing a signal/or no signal from something like the ECT sensor, now you can also do this right at the CCRM which would be easier on pin 17 but the reason I tell you to go to the PCM is to also eliminate a wiring problem.
You said you replaced the sending unit was this the sending unit for the gage or the ECT sensor for the PCM. The ECT will have 2 wires to it(LG/R and GY/R). and is located near the back of the upper intake manifold right next to the fuel pressure regulator. If this is unplugged or has an open circuit it will do the same thing.
Here is a pic of the connector at the CCRM
Do this before the steps I have listed first about grounding the pin at the PCM or the CCRM
Now you can measure the resistance values at the ECT and this is what they should read depending on the temp. of the coolant.
There are only 24 pin connections on the PCM. Where is number 31?
I just thought I would let you know what was going on. I tried the things you mentioned. However, the light bulb lit, when I remembered that my A/C hasn't ever worked on my car. I tried several things to get it to work during the summer, but had no luck. I thought that maybe my playing around somehow caused the problem with the cooling fan in the first place.
There is a small aluminum cylinder shaped object hooked up to what looks like a vacuum line near the A/C compressor. When I disconnected the wires (plug) from that, the electric cooling fan went off. Remembering that the cycling of the cooling fan is also connected to the A/C, I unplugged this unit. Now, the engine warms up to operating temperature (according to the temperature gauge on the dashboard), and the fan comes on when it gets hot, and as the temperature falls, it turns off, just like it should.
What is this cylinderical unit with the vacuum line running out of it near the A/C compressor? Maybe this is also the reason the A/C doesn't work either. Let me know, or I can call to talk with you, if that is easier.
Well what I think you are talking about is the refrigeration containment switch. It is not in a vacuum line but in the high pressure AC line . It operated the high speed fan from 1000 rpm when pressures below 150 psi to 1800 rpm with refridgeration pressures over 250 psi.
Does it have 4 wires to it with colors being T/LG,PK/LB,RY,BK. ?
Not sure about the wire colors, but definitely has 4 pins/wires. That must be it. There is no pressure in the system, because all the coolent has leaked out of the A/C. I guess that would make the fan come on if there is no pressure.
Since I have your attention, my tachometer on the dash only works intermittently, on accelleration, but drops back down shortly thereafter. How can I fix that? Is it an electric tachometer, or is there a cable?
Also, I get a lot of interference on my radio when listening to an AM station. Especially when I use the cruise control, or when I accellerate, the noise increases. Sounds like it is coming from the alternator, a high pitched whine.