94 thunderbird radiator fan/ temp gauge problem

[frustrated by now]

I recently bought a 1994 Ford Thunderbird LX 4.6L V8. There are no trouble codes. Its all good except the radiator fan will not run, and neither will the temp gauge. Anyway, here’s what I found: Both high and low speeds work on the fan when “hotwired”, so the fan is good and so is the ground. The fuse is good and has power to it. I replaced the coolant temp sending unit on top of the block and now the temp gauge works, but only about half way. I’ve noticed there are other temp sensors in the block; I would like to know what they are for as they are not indicated on technician’s diagrams. I replaced the IRCM with one from a junkyard and there was no change. There is always 6 volts to the fans low speed when the key is on, but it doesn’t seem to be enough to run, because it works with 12V when “hotwired”. There is never current to the high speed , even when the engine is warmed up and the radiator is too hot to touch. I heard somewhere that the high speed only comes on when the A/C is on, but it was removed before I bought the car. There are a lot of cut A/C wires though, I wonder if that has anything to do with it? Although the low speed doesn’t work either… Anyone have any ideas(fan or temp gauge)? It would be a huge help.

[97Bird]

You can get a factory electrical and vacuum troubleshooting manual (EVTM) on Ebay for about $15. This will show you where all of the cut wires are supposed to go. I have one of these manuals for a 1997 and it shows two coolent temp sensors on the 4.6. The one on the top left side of engine, near the left side of the alternator, is for the guage. The one to the right back of the alternator goes to the PCM and for one thing is used to tell when to turn on the cooling fan.
A 12V supply from a 60A fuse goes to the CCRM (IRCM) and passes through either the low speed relay or high speed relay before going to the fan motor. I don't see any reason for any voltage other then something very close to 12V being being at either the low or high speed wire of the fan. Remove the connector from the fan motor and measure the voltage at the low speed wire. Connect the low side of your meter directly to the battery's negitive terminal when taking this measurement. With your meter set to the ohms scale, take a measurment from the black wire's terminal in the connector (ground wire) to the battery negitive terminal. Let me know what you get for these readings.
Again, I'm going by a 1997 manual so your's may be different.

[frustrated by now]

hey thanks for your help:
Anyway, I measured 6.5 Volts on the low speed, none on the high. There are .5 ohms from the ground to the battery terminal, measured from the 20k setting
(im pretty sure the engines are the same)

[97Bird]

If you only have 6.5V at the connector, with it disconnected from the fan motor , then you have something else connected into that circuit that is drawing current. On a 1997 the circuit goes from the 60A fuse to pins #3 and 4 of the CCRM connector and then to one side of the low speed and high speed relay switches. The other side of the low speed relay switch goes to pins 1 and 2 of the connector. From there it goes directly to the low speed wire in the fan connector. The other side of the high speed relay switch goes to pins 6 and 7. From there it goes directly to the high speed wire in the fan connector. The 1997 has pins 1-12 in one row with pin 9 not used and pins 13-24 in the other row with pins 19 and 20 not used. Pins 1 and 13 are on the same end of the connector. I don't know if the CCRM is interchangable between years so you should make sure you have the correct one. If the engine is cold then you shouldn't have any voltage at the fan motor connector. Check to see if you have 12V at the fuse and input to the CCRM. You can disconnect the battery and then use the ohmeter to trace the circuit from the fuse to the CCRM.

[frustrated by now]

Alright i checked the ohms from the fan motor fuse to every pin; Pins 3, 4, and 5 have 0 ohms, the rest have 1/infinite. Pin 5 is for the fuel pump though, shouldn't there be resistance there?
I have tried replacing the IRCM with one from a junkyard, but there was no change. It is possible both are junk. The thunderbird in the junkyard had a blown engine, so it may have had the same fan problem and overheated, i dont know...

[97Bird]

On a 97 the pin 5 is a relay output to the fuel pump. The input side of the relay switch goes to pin 11. Check the continuity between these two pins (check your diagrams to see if these pins are the same on your 94). With your battery disconnected there should be no continuity between these pins (infinite resisitance). If there is then you are seeing continuity between pin 5 and the cooling fan fuse because these two points are connected to the positive side of the battery between their seperate fuses. This also means the fuel pump relay is stuck closed.
Are you seeing the 6.5V with it unplugged from the motor? Is there any voltage present on the low side of the motor when the engine is cold? What is the voltage at the CCRM pins 1, 2, 3 and 4? Does my description of the CCRM connector agree with your diagrams for the 94 (pin #'s and pins not used)? Do your diagrams show the inside of the CCRM?

[frustrated by now]

The pins seem to be the same on the 1994 as your 1997. Pins 9,19 and 20 are not used. My diagrams show the inside of the IRCM.
There is no continuity between pins 5 and 11, so the relay is open (the battery is disconnected). Pins 3 and 4 are power going into the IRCM, they both have 12.6 volts. Pins 1 and 2 are going out of the IRCM. Pin 2 has 0 volts, pin 1 has 0.02 volts. Somewhere they link with a wire coming from the Powertrain Control Module. The PCM wire is putting out the 6.5 volts whenever the key is on(engine cold). It goes through a fuse(which is good), and eventually to the low speed on the fan motor. The high speed still has no volts.

[97Bird]

In my second post I describe the full path from the fuse to the fan motor. There is no connection to the PCM in the actual fan circuit. The PCM controls the windings in the high and low speed relays which in turn opens and closes the relay switches. One end of the low speed relay winding goes through a solid state relay control and then to ground through pin 15.The SS relay control is sent a signal from the PCM pin 45 through pin 14 of the CCRM. The return from the high speed relay winding goes through pin 17 and then to the PCM pin46. Does your diagram agree with the circuits as I described them? You are going to have to trace the wire with the 6.5V to see how it is getting connected to the fan circuit. What is the PCM pin # that has the 6.5V on it?

[frustrated by now]

The pins on the PCM are completely different on the 94, so are diagrams are different. Is there a way I can send you mine, or do you have one, or can you help with what i can tell you?

[97Bird]

You can attach an image to a private message to me. It sounds like the pinout is the same on the CCRM's though. Is this correct? Send me the diagram and tell me what the pin is named that has the 6.5V on it.

[97Bird]

What years are these diagrams for? Just 94? Remove the 10A fuse that is coming from the PCM pin 4 and see if you still have 6.5V on one side of the fuse holder and which side it is on (PCM or Fan side). A 97 doesn't have this connection back to the PCM pin 4.

[frustrated by now]

So far as i know they're just for 94. The 6.5 volts is on the PCM side.

[97Bird]

The PCM wiring is very close between the two years but the 97 doesn't have the connection back to the PCM from the fan like your 94. I'm sorry but I have no idea what signal is supposed to be coming from the PCM pin 4. I wouldn't think it should be 6.5V though. You'll need the Powertrain Control manual for PCM diagnosis or maybe you could ask at your local dealer what should be happening on that pin. You should still trace and repair any of the cut wires that you find. Here is a site for the manual. http://www.auto-repair-manuals.com/F...ce-Manual.html There are some websites that you can ask a Ford tech for answers so try one of those sites also. If you find out, please let me know.

[97Bird]

Is there any chance you can get the PCM out of the car you got the CCRM from and trying that to see if you still get the 6.5V? Put your original CCRM back in and with the key on see if you have 12V at pin 17 and tell me what the voltage is on pin 14

[frustrated by now]

I dont have access to the other car so i cant check its pcm, but ill the original CCRM and see if its any different. Do you need me to send the missing diagram?