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HDGENE, Ford Senior Master/Diesel/Trans
Category: Ford
Satisfied Customers: 5130
Experience:  25 years Auto experience, Ford ,GM, Chrysler, Asian & European
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Ron, I would like to ask you about your posting to "rick"

Customer Question

Hi Ron, I would like to ask you about your posting to "rick" with his cooling fan problem.
Submitted: 8 months ago.
Category: Ford
Customer: replied 8 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  HDGENE replied 8 months ago.

Hello, it looks like Ron isnt available at the moment can I be of assistance? What type of concern are you having with the fan?

Customer: replied 8 months ago.
I performed every step Ron posted to a customer (Rick) with the problem of the 2-speed fan never coming on. Ron's post said:
Expert: Ron
Hello Rick,
The cooling fan is controled by the signel from the ECT and the PCM turns the fan on usually when the engine
reaches about 225 degrees.
This system is designed to maintain engine temperature by using the low speed cooling fan only. The high speed
fan circuit is incorporated as a fail safe to be used only when engine temperature exceeds 230 degrees. There
are 2 fuses involved in this system. The first is in the engine compartment fuse box. This fuse is labeled cooling
fan. It is a 40 amp, hot all the time fuse that supplies the fan through a combination of relays. The second is in
the interior fuse box. This is a 15 amp, key powered fuse, labeled engine. It is used to energize the first relay. If
the engine runs, this fuse will be good. Test the 40 amp fuse. If defective, replace and retest the fan operation. If
OK, go to step 2.
To test the Cooling Fan Power Relay, which may also be called the Ignition Relay, remove the relay from the
engine compartment fuse box and using a 12 volt testlight, check for 1 terminal to be hot all the time (coming
from the 40 amp fuse), 1 to be hot with the key on (coming from the 15 amp fuse), and 1 to be a good ground.
To test the output of the relay, gain access to the cooling fan high speed relay. It is mounted with the cooling fan
low speed relay and is located on the front of the left front strut tower near the bottom where it meets the frame.
The high speed relay will have a blue connector and 5 terminals. Using a 12 volt testlight, turn the key on and
check for voltage at the Light Green/Black wire at the relay. This wire comes from the cooling fan power relay in
the engine compartment fuse box. If there is no voltage, replace the Cooling Fan (Ignition) Power Relay and
retest the system operation. If voltage is present, go to step 3.
To test, gain access to the Low Speed Cooling Fan Relay. This relay is identified by the black connector with 4
cavities. Using a 12 volt testlight and key on, backprobe the Light Green wire to test for voltage. If no voltage,
repair the open circuit from the high speed cooling fan relay. If this test OK, test the Black/White wire for voltage.
If none present, repair the open circuit from the 15 amp engine fuse. If this tests OK, check the voltage on the
Yellow/White wire using a digital voltmeter. It will read under 1 volt if the engine temperature is under 220
degrees. This wire is held to ground by the Powertrain Control Module (PCM) until engine temperature reaches
215 to 220 degrees. At that time it releases the ground to energize the relay and turn on the low speed fan. To
test the relay operation, backprobe the Yellow wire with a 12 volt testlight. Remove the Yellow/ White wire from
the connector and turn the key on. The relay should click, the Yellow wire should now be 12 volts and the fan
should be running. If there is no voltage on the Yellow wire, replace the Low Speed Cooling Fan Relay and retest
system operation. If voltage is present and the fan is not running, go to step 5. If voltage is present and the fan is
running, go to step 6.
To test, verify the key is on and the Yellow/White wire is removed from the low speed cooling fan relay connector.
Check the Black wire at the cooling fan connector for a good ground. If it tests OK, test for voltage at the Yellow
wire at the cooling fan connector. If no voltage is present, repair the open circuit between the low speed cooling
fan relay and the cooling fan connector. If this tests OK, replace the cooling fan. Retest the system operation.
To test, gain access to the powertrain control module (PCM) and unhook the connector. Locate the Yellow/White
wire at pin 35 and test for a short to ground between the PCM and the low speed fan relay. If it is shorted to
ground, repair the wire and retest the system operation. If this is OK, reconnect the PCM connector. Locate pin
7, Dark Blue/White wire, and backprobe it with a digital voltmeter. Pin 7 is the input to the PCM from the Engine
Coolant Temperature (ECT) Sensor. Start the engine and monitor the voltage as the engine warms up. If
possible, also monitor the engine temperature with a thermometer or temperature gun to compare the ECT
sensor voltage with actual engine temperature. The voltage decreases proportional to engine temperature. A
reading of 0.6 volts equals 195 degrees. The cooling fan will be turned on by the PCM when voltage drops to
between 0.55 and 0.45 volts or 215 to 220 degrees of temperature. The failsafe or high speed fan would come
on when voltage reaches approximately 0.41 to 0.39 volts indicating 230 degrees has been reached. If engine
temperature gets hot and the ECT sensor voltage does not drop to inform the PCM of actual temperature,
replace the ECT sensor and retest the system operation.
Expert:  HDGENE replied 8 months ago.

Ok so the fan never comes on with the ac on or when the engine reaches 225? Have you tried jumping power and ground to the fan directly to see if it will operate?

Expert:  HDGENE replied 8 months ago.

Do you have power at the fans with the ac on and ground and they dont operate? Im not sre what youre test results are?

Customer: replied 8 months ago.
Everything checked out OK.... I also previously replaced the ECT sensor and temp sensor (used by the PCM and the factory analog temp gauge, repectively). The most interesting test (last paragraph from Ron) was to check the pins 7 <ECT output to PCM input>, 35 <PCM output to the Low Speed Relay coil Gnd2Energize>, and 31 <PCM output to the High Speed Relay coil Gnd2Energize>. I verified that these three PCM Connector pins are not shorted or open and connect to the ECT, Low Speed Relay coil, and High Speed Relay coil, respectively. I also left the PCM connector disconnected from the PCM, turned the Key to the Run position and verified that with Pin 31 High/Floating + Pin 35 Low/Grounded=> the FAN IS OFF, with Pin 31 High/FLoating + Pin 35 High/Floating=> FAN IS ON at Low Speed, with Pin 31 Low/Grounded + Pin 35 High/FLoating=> FAN IS ON at High Speed, ...and with Pin 31 Low/Grounded + Pin 35 Low/Grounded=> FAN IS ON at High Speed! This Matches the Factory Ford schematic on page 03-03-14 of the 1993 Escort/Tracer March 92 shop manual! >> With the PCM connector connected to the PCM and the engine running, I monitored the voltage at Pin 7 with a Fluke DVM and watched as the voltage gradually decrease (just as Ron described in the last paragraph).... as the ECT voltage hit 0.6 volts and continued dropping, the factory temp gauge was at the middle temp reading BUT NO FAN (the fan Low speed should have kicked on). I continued to watching the engine warm up as the ECT voltage hit 0.55 and down to 0.45 volts - still NO FAN, factory temp gauge is almost 3/4 scale, I let the ECT voltage drop further to 0.20 volts - Still NO FAN !! >>>So, I verified all the wiring, relays were removed and tested on the bench for coil pick, and connections between the COM, NO, and NC terminals of the High Speed Relay + coil, COM, NC terminals of the Low Speed Relay, verified that the 'digital' control signals Pins 31 and 35 from the PCM connector does control the 4-signal combinations to control the Fan to OFF, LS ON, and HS ON, ..and the ECT voltage signal is working properly at the PCM connector. BECAUSE everything to but the PCM checked out ok and works when manually controlled AND the PCM is getting the correct ECT voltages, I concluded that the PCM must be bad. So, I ordered a "100% tested PCMs" from Cardone Industries who sells Guaranteed Rebuit PCMs matching my PCM (F3CF - MA) and I installed it AND THE FAN STILL DOES NOT WORK! I'm going to call Cardone Industries tomorrow. So my QUESTION IS: Does the PCM need any other input information that is used to control the fan ? NOTE: I also checked out the a/c Relay... could not find anything bad + the fan has worked for over 5 years since the a/c compressor blew & freon leaked out, so I know the engine fan will work w/o the a/c (and the circuity is such that the a/c is just another separate circuit used to force the fan on when the a/c is on...but it hasn't worked because the a/c pressure switch is off due to loss of freon + I disconnected the compressor power connector (because my wife used to turn it on when the defroster was on and I didn't want the compressor clutch to engage and do more damage to the a/c system).So the QUESTION still is, Is there some other input that the PCM needs to turn on either the Low Speed or High Speed fan?NOTE: I can simply unplug the PCM connector from the PCM and turn the Key on Run, and the Low Speed fan will run (of course the Engine wont' run without the PCM)....this makes sense because the Low Speed Relay coil is not picked => NC to COM connection supplies power to the Yellow wire to the low speed fan motor tap AND the High Speed Relay coil is also not picked => NC to COM connection connects the the 40A 12V power COM input directly to the COM terminal of the Low Speed Relay --- Making the FAN RUN at Low Speed.====> I need to know if there is some other input the PCM needs ...hopefully BEFORE I talk to Cardon Industries to 'argue that their 100% Tested PCM module is defective. I Do Know that my PCM module will pass the 'poorly early generation ECM/OBD2 tests .... BOTH KeyOnEngineOff ..AND... KeyOnEngineRun TESTS PASS with my old PCM & the new PCM!H_E_L_P --- PLEASE ADVISE!
P.S. I'm a retired Electrical Engineer and fully understand the circuit/connections OUTSIDE of the PCM... I have my suspicions of what circuits can cause the problem inside the PCM ...BUT will Void the warranty if I 'open it up'... so I can't do anything with it.Any help you can provide would be greatly appreciated!!Thank you!!
Customer: replied 8 months ago.
Anxiously awaiting your Reply!!!! - Henry
Customer: replied 8 months ago.
PS In answer to your questions: 1) yes the fan works, I can connect 12v to the low speed wire (at the low speed relay connector) and the fan runs + connect 12v to the high speed wire (at the high speed relay connector) and the fan works.As far as the a/c goes.... in my response, the fans worked for over 5yrs without the ac because the ac went out a long time ago when the compressor blew/froze after the high pressure hose blew. The only effect to the fan was it didn't go on when the a/c dash switch was turned on OR the defroster was turned on <which also turns the a/c>.... otherwise the fans worked fine w/o the a/c working. Also, I did check out the circuit for the a/c to see if there was any problems there (using the schematic on page 12-03A-15 of the factory Ford shop manual.
Customer: replied 8 months ago.
PSS ...I did check the ground from the motor to Neg battery terminal for excessive resistance using the Ohm meter of the Fluke too. Also, checked the Ground pin (pin 60 of the PCM connector for excessive gnd shift of more than 0.2volts and it was 0.13volts) so it's getting a good ground connection.
Expert:  HDGENE replied 8 months ago.

Ok so the fans will operate on both low and high speeds when performing a Key On Engine RUnning On Demand test and sets no codes and you dont know if the fans come on when the ac is running since the ac is inop. But basically they wont come on low or high when it reaches normal operating temperature and causes the car to overheat? All the testing is good, it will run if jumped, it will run if you jump across the relay and you have tried different relays?

Customer: replied 8 months ago.
No.... the KeyOnEngineRunning (KOER) test does NOT test the fans, also the KeyOnEngineOff (KOEO) does NOT test the fans. The only symptom that the fan works during normal operation is during KOER for the second or so when the starter is cranked Before the Engine runs (due to the Starter Relay being engaged BEFORE the PCM Relay switches power to the PCM which results in a brief voltage to the fan low speed Yellow wire before being cut off by the PCM picks the Low Speed Relay - killing the power to the fan.I was able to have total control by DISCONNECTING the PCM connector to the PCM and manually floating or grounding pins 31 and 35 to turn on the fan at high speed (with 00 or 01 pin combo), turn on fan at low speed (with 11 pin combo) and finally turn off the fan with (11 pin combo).I was able to contact Cardone Industries Expert tech support.... they are checking to see if they test pins 7, 31, & 35 to see if they really do 100% testing on the PCMs they sell (especially the one they sent me. ==> So unless you have some other PCM inputs that are used to control the HS and LS fan relays, I guess the problem must be the PCM. Thanks!
Expert:  HDGENE replied 8 months ago.

Thats right, it should run the fans on both speeds Key on engine off, if not, it should set a code if they dont kick on. Have you replaced the fan relays? It sounds like a PCM.