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Discussion Starter · #1 · (Edited)
i just got done swaping in a new motor and it started fine, no issues, no cel lights. however, after running it for a little longer two problems arose:

1. idle was about 1500 at first then dropped down to 1000 after about 15 seconds...

2. cooling fans don't come for high temp or a/c ...

after searching the forum i have tried to troubleshoot/diagnose the following:

working backwards from the fans...they both work fine jumpered directly to 12v

unplugged the harness under the battery and applied 12v to both the high speed and the regular fan lead, both worked fine

plugged the harness back in and pulled both relays, applied 12v to the fan side of both reg/high speed fan, again both times the fans came on

then jumpered the 12v high amp side of both relay sockets and again both times the fans worked

with the key in the run position and the a/c on i measured the relay side of both sockets, leg 1/2, and again got 12v

i turned the a/c off but still got 12v on that same leg. when i turned the key off run, the 12v went off

i took both relays and applied 12v to legs 1/2 and the relay engaged and showed continuity across the the switch side....and none when 12v was not applied


now by all that i know, the fans should be running when i turn the key to run, but they are not and i have no idea what to check or do next.....help

since i bought the car with a blown motor, i have no idea if the prior owner had the same problem...


also, i noticed that the fans would not come on when the engine temp gauge started climbing close to the red and they were not on. i then checked the engine temp via the diagnostic panel and it was at 235, which i have learned is beyond the point of fan engagement...
 

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first off, did u use a meter or test light to check this stuff? can make a difference, but probably doesnt matter.

second, did u make sure the control pin is receiving ground from the ecm? ill look on my service disc to double check, but im pretty sure those relays are computer controlled by ground to turn on. just because you have voltage doesnt mean they are supposed to come on. im not trying to bust your chops, just been a long day and cant think hard enough to phrase this stuff nicer. :beer:
 

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Discussion Starter · #3 ·
i checked it with a meter...

i did not check the control pin, but as i recall one of the relays had only four spade connectors, one of them had a much smaller 5th connector, which i assume you are referring to...

i can check that pretty quickly if that is what you mean...just let me know how to check...

i checked both relays though and they engage when voltage is applied to pins 1/2 and then pass current....

as i recall the low speed relay has the 5th pin...does that mean if it is bad the fans won't come on at all, even with the key in the run position and the a/c on ?
 

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1st the RPM difference could be pretty normal. Mine revs to slightly less for a bit longer. But 1k idle is perfectly acceptable.

2. i think your going to find the problem is the multiple temperature sensors on the block. One goes to the dash one goes to the fans via the ECU (i think been a while). That 2nd sensor where ever it is, is probably not working right or connected ... something like that.
 

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i checked it with a meter...

i did not check the control pin, but as i recall one of the relays had only four spade connectors, one of them had a much smaller 5th connector, which i assume you are referring to...

i can check that pretty quickly if that is what you mean...just let me know how to check...

i checked both relays though and they engage when voltage is applied to pins 1/2 and then pass current....

as i recall the low speed relay has the 5th pin...does that mean if it is bad the fans won't come on at all, even with the key in the run position and the a/c on ?
Just having the AC on will not neccisarly turn on that fan.
 

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There are 2 temp sensors on the water crossover, between the heads. The one facing the firewall is for the ECU; the one facing to the side is for the temp gauge.

Also - could this be because the AC isn't charged with "freon"? Does that affect the fan operation?
 

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...as i recall one of the relays had only four spade connectors....
quick note on relays....i think its posted somewhere, but ill say it again.....

4 pin : pin 30 - source voltage ( 12v )
pin 85 either key on power or ground
pin 86 opposite of 85
pin 87 to component, fan in this case.
5 pin : same w/ pin 87a....sends voltage somewhere else when relay is not energized.



should have 12 v to 30, 12 to 85 or 86 and 0 v to the other, and 12 volts to fan when relay is energized. ill look up the schematic, but in a nutshell, you should have 2 connectors (relay unplugged) with 12v with key on. when car is hot enough for fans to kick on, you should have a ground signal on one of the others, so take your meter on voltage, red to battery + and black to a terminal. should show up 12 v if its grounded.

im gonna get that schematic and give some more specifics.
 

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Discussion Starter · #9 ·
first off, did u use a meter or test light to check this stuff? can make a difference, but probably doesnt matter.

second, did u make sure the control pin is receiving ground from the ecm? ill look on my service disc to double check, but im pretty sure those relays are computer controlled by ground to turn on. just because you have voltage doesnt mean they are supposed to come on. im not trying to bust your chops, just been a long day and cant think hard enough to phrase this stuff nicer. :beer:
i checked leg 7, and it is grounded with ignition off and i get about 35 Ohm resistance with key in run position

1st the RPM difference could be pretty normal. Mine revs to slightly less for a bit longer. But 1k idle is perfectly acceptable.

2. i think your going to find the problem is the multiple temperature sensors on the block. One goes to the dash one goes to the fans via the ECU (i think been a while). That 2nd sensor where ever it is, is probably not working right or connected ... something like that.

There are 2 temp sensors on the water crossover, between the heads. The one facing the firewall is for the ECU; the one facing to the side is for the temp gauge.


Also - could this be because the AC isn't charged with "freon"? Does that affect the fan operation?
which sensor does the diagnostic panel go to, because i checked that and got a temp reading...

a/c compressor clutch engages...
 

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Discussion Starter · #10 ·
quick note on relays....i think its posted somewhere, but ill say it again.....

4 pin : pin 30 - source voltage ( 12v )
pin 85 either key on power or ground
pin 86 opposite of 85
pin 87 to component, fan in this case.
5 pin : same w/ pin 87a....sends voltage somewhere else when relay is not energized.



should have 12 v to 30, 12 to 85 or 86 and 0 v to the other, and 12 volts to fan when relay is energized. ill look up the schematic, but in a nutshell, you should have 2 connectors (relay unplugged) with 12v with key on. when car is hot enough for fans to kick on, you should have a ground signal on one of the others, so take your meter on voltage, red to battery + and black to a terminal. should show up 12 v if its grounded.

im gonna get that schematic and give some more specifics.
i did all that, but i was not using the right terminology and got the readings you indicate i should.

i understand how a relay works and it was doing what it was supposed to be doing, assuming that the connection is good enough to pass the amperage required to power the fans and not just the test voltage for continuity across the source and component legs.

so if one of the relays is bad, should the fan at least work on the other speed, or does for example, a bad high speed relay or a reg. speed relay or vice versa mean that the fans don't work at all ?

if not, what are the chances of both relays going out ?

very strange....
 

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I would check the Temp Sensor that is under the EGR valve (about 5-6 inches below it and its located on the water crossover pipe on the rear head nearest the firewall...

The one sensor you said you checked is the Temp Sending Unit for the gauge cluster... the one to look for is the Temp Sensor that reads temperature and sends the info to the ECU to kick on the fans...
It is most likely not connected, or even broken... Pretty easy to replace if broken...

My $$$ is on it not being connected.
 

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Interesting stuff from an old post ... coppied from the ford CD.


The powertrain control module (PCM) determines the cooling fan motor requirements and controls the fan operation through the low speed fan control and high speed fan control outputs. The PCM outputs complete the ground side of the relay coil circuits. Power to the relay coil circuits is provided by the PCM power relay.

If low speed fan operation is required, the PCM grounds the low speed fan control output. This energizes the low speed FC relay coil which closes the low speed FC relay contacts. Power flows through the fuse 2 (60A), the low speed FC relay contacts, the engine cooling fan resistor, and the engine cooling fan to ground. The engine cooling fan resistor provides thermal overload protection for the low speed fan control circuit.

If high speed fan operation is required the PCM grounds the high speed FC relay coil which closes the high speed FC relay contacts. Power flows through the fuse 2 (60A), the high speed FC relay contacts and the engine cooling fan to ground.

High speed fan operation may also be commanded by the dual pressure A/C pressure switch. The medium pressure contacts of the A/C pressure switch turn on the high speed cooling fan when A/C head pressure reaches a predetermined level grounding the air conditioning pressure switch. This grounds the high speed FC relay circuit. This closes the high speed FC relay contacts and turns on the high speed cooling fan.

If A/C head pressure drops below the predetermined level, the medium pressure contacts open returning the high speed FC relay operation to the PCM.
 

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Discussion Starter · #13 ·
ok, now i am really stumped....

started the car to see if in fact a/c was working, and guess what...the fans worked just like they are supposed to

but i still wonder what sensor the diagnostic console draws info from, the one by the firewall, or the one facing the intake box...

hopefully they will continue to work :eek:

i must have jolted something without knowing it and now it makes contact, which is not good, i hate intermittent problems, very hard to track down
 

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Well... definitely something to keep an eye on for a while. You might think about installing a better temp gauge in another position; perhaps a pillar pod or something.
 

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Discussion Starter · #15 ·
yeah, or a manual override switch for the fans....

'cause the gauge read hot, that's how i found out the fans didn't work, temperature kept going up, but never got into the red, so i think i caught it before it did any damage....i hope !!
 

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Are you speaking of the needle gauge on the dash as the guage you were watching? If it was, check the computer gauge on the temperature read out for a better reading of the water temperature.

I think this is the process for getting it into diagnostic mode, or whatever it is called: 1.) hold reset + units 2.) Start car 3.) release reset 4.) release units 5.) push select until you get to the diagnostic item you are wanting to see, should say something about water temp on it, if I remember correctly.

I'm sure someone will be along very shortly to correct my mistakes above.

The gauge you, I think, are talking about is only an "estimate" of the temperature. It should read about halfway when the car is fully warmed up.
 

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Don't know if this will help you in anyway. But it's something i posted a while back. If anything, it might help somebody else...

 

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Discussion Starter · #18 ·
Are you speaking of the needle gauge on the dash as the guage you were watching? If it was, check the computer gauge on the temperature read out for a better reading of the water temperature.

I think this is the process for getting it into diagnostic mode, or whatever it is called: 1.) hold reset + units 2.) Start car 3.) release reset 4.) release units 5.) push select until you get to the diagnostic item you are wanting to see, should say something about water temp on it, if I remember correctly.

I'm sure someone will be along very shortly to correct my mistakes above.

The gauge you, I think, are talking about is only an "estimate" of the temperature. It should read about halfway when the car is fully warmed up.
no, the temp. reading i was talking about was the one that i got by pressing the reset/units then select button and i wonder which sensor that reads from...
 

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no, the temp. reading i was talking about was the one that i got by pressing the reset/units then select button and i wonder which sensor that reads from...
If I had to guess, I'd say the Engine Coolant Temp Sensor, since the ECU would be needed to drive the LCD display in the instrument cluster. If I remember, I'll try to check the wiring schematics and see if it makes it clearer.

But I'm sort of in the middle of moving, so it may not happen tonight.

If it's not too hard to get to, would it be possible to just unplug one sensor at a time, and see which gauges/displays go out?
 

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Discussion Starter · #20 ·
i thought of that too, but i won't be home until later tonigt to try that, i just thought someone might know off the top of their head....:)

i'll inspect the connection to the back sensor too and may just swap it out for the one off the old motor....
 
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