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Discussion Starter · #1 ·
Mike or someone else, I realy need help!!

A few weeks ago the main cooling fan starting running all the time when the car was running. It didn't matter if the car was warm or cold, you start the engine, the cooling fan comes on. I pulled the error codes and got a code 9, engine coolant sensor. According to Mike's site if this fails it will cause the colling fan to come on all the time. I checked the resistance on the sensor and it failed so I just replaced the sensor thinking all would be well. It wasn't, the problem still exists. The car runs fine otherwise, shows the correct operating temperature, nothing else appears to be wrong. Unfortunately the Haynes manual I have doesn't help to address this problem, so I need some help.

I noticed on Mike's site that for my 93PGT that there is also an ECT-F (engine coolant temperature-fan)sensor that if it goes bad, will also cause the fan to stay on, but I am not pulling this code. Does anyone know where this sensor is located???
Another couple of thoughts are that just to the right of the ECT on the front of the engine there is a cooling fan sensor (per the Haynes book). Does anybody know what this does, and the exact resistance I should be checking for to see if this works?? I am not sure if this could be the problem or if it just controls the speed of the fan, not necessarily on/off. If you unplug it while the car is running, nothing happens, car keeps running, fan keeps running.
I also notice that there is a fan relay just in front of the rad, on the passenger's side. Does anybody know exactly how to check that to see if it working properly?? The Haynes book doesn't give any details at all.
I am stumped. I really need your help!!
 

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1993 V6 cars used two coolant temperature sensors. One was used for the cooling fan operation (ECTF) and one was used for fuel and spark calculations (ECT). Both are located in the same vicinity near the radiator cap on the timing-belt side of the engine. In this area there are actually 3 sensors.

One of them has only one wire going to it, that sensor is used by the instrument cluster temperature gauge and has no bearing on cooling fan operation.

The ECTF sensor is screwed into the radiator-cap housing itself and has two wires coming out of it.

The ECT sensor also has two wires an is situated roughly between the ECTF and temp-gauge sensors.

If either of the ECT or ECTF sensors has opened or shorted or the wiring or connectors is bad, the cooling fan(s) will come on as a safeguard against overheating since the PCM can't accurately determine the engine temp: better safe than sorry.
 

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Discussion Starter · #3 · (Edited)
Thanks for the reply Mike. So the ECTF is what Haynes calls the cooling fan sensor. The part I can't understand is that if either of these is not functioning, would it not store the error code in memory?? I found the code 9, but I didn't find a code 69. Would a short in the wires cause an ECTF code to NOT show up?? I will try the OHM testing on the ECTF tonight. One thing I did notice is that both the old and new ECT sensors showed the same resistance at room temperature, about 2150. I am assuming that is close enough to the 2200-2700 as indicated in the manual, or could both sensors (old & new) be bad?? The car does not pull a code 9 anymore, but then again it doesn't pull a code 69 either. I am trying for the least expensive fixes first, and praying it isn't a short or a PCM failure.
Also, once I pull the relay to check that as well, exactly how do I check it?? Ohmmeter or something else and what should it read. I really got to try and get a proper service manual. Seems not too many people want to ship to Canada!!
 

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Discussion Starter · #4 ·
Update

I checked the resistance of the ECT-F last night. At room temperature the resistance was 2300 ohms, which seems to be within specs, but when the engine is at normal operating temperature, the resistance is 2100 ohms. According to your site Mike, the resistance should be somewhere between 220-250 ohms, so I think this may be the culprit. Funny how it didn't show any error codes when I checked. I thouhgt it would show a code 69 if this thing failed. I'll try to find a replacement and see if that does the job.
 

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Re: Update

saint said:
I checked the resistance of the ECT-F last night. At room temperature the resistance was 2300 ohms, which seems to be within specs, but when the engine is at normal operating temperature, the resistance is 2100 ohms. According to your site Mike, the resistance should be somewhere between 220-250 ohms, so I think this may be the culprit. Funny how it didn't show any error codes when I checked. I thouhgt it would show a code 69 if this thing failed. I'll try to find a replacement and see if that does the job.
Hmm. I haven't looked at the PROM code lately for the ECTF sensor but I'm not certain that a reading like this would cause the code 69 to trip. It may though...

For most resistive-type sensors like the IAT or the ECT, the PCM simply check to see if the circuit/sensor is open (very high resistance causing high input voltage) or if the circuit/sensor is shorted to ground (very low resistance causing very low input voltage.)

In order for what you observed to cause a code, the PCM would have to be comparing the ECT and ECTF sensor inputs (which I'm not sure of).

Certainly, a resistance close to 2Kohm when running hot isn't right, so that needs to be looked at.
 

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Discussion Starter · #6 ·
I am at a Loss!!

Well, I replaced the ECT-F last night. I verified that it was the right part number. I STILL have the same problem. I checked the resistance on the sensor and it was 2300 cold. After I let the car warm up to normal operating temperature the resistance was at 3400 ohms!!:eek: :eek: When I checked Mike's site it said the resistance should be about the same as the the normal ECT. My ECT is 2350 cold and about 350 warm (within specs).
Mike, should the resistance for the ECT and the ECT-F be follow the same logic (around 2300 cold and 25-350 warm??). I am at my wits end with this thing now. Does anybody have 93 Ford/Mazda Service Manual that would state what the correct resistance would be for the ECT-F just to double check???
I am also thinking whether the relay or the wiring is bad. Any ideas as to how I check the wiring?? Can I just start the car, unplug the ECT-F sensor and stick the multimeter probes in the 2 contacts and test the voltage?? If so, what should the voltage be?? Haynes is useless in this regard. How do I check if the relay is bad. It seems to be a PITA to get to and unplug (not much room to get at it in front of the rad). HELP!! :V
 

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Discussion Starter · #7 ·
Might have apporached this wrong!!

When you open the car and look at the engine, the fan that keeps running is the one on the passenger side, NOT the one on the driver's side. I just assumed that the passenger side fan was the main cooling fan, but is this actually the A/C fan?? If it is then I am not sure why it would keep running. I don't use the A/C at all this year (not warm enough yet), although the A/C does work. Which fan is this??
 
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