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I have a 2000 coupe my high speed cooling fan doesn't always come on.I have replaced relays and 30 amp fuse.Nothing wrong with ones I removed.No codes with snap on scanner.I can turn on and off no problem with scanner.Then car might work for a bit on own or not.Is there a sensor that turns it on?I Ican read 236 degrees on dash and still doesnt come on but car will cool off till around 220 without it.Any help is greatly appreciated!
Here is the description of the low speed fans operation and the high speed fans . (Both fans are operationg on low speed and high speed .
When ECT goes above 219 F degrees , the PCM ground Mini Relay 43 and 44 and both will be energized .
I measured both C1:42 and C2:33 when the fans was turned off and got commanded to high speed using my Tech2win scanner (both fans got 12 volt).
The result is shown on the last picture When high speed is commanded by the PCM both C1:42 and C2:33 got grounded .
You can check if the voltage level on C2:33 drops from 12 volt to 0.1-9.2 volt when temperature hit 219 F degrees
I will have to look at it a little each of next few days sounds like I might have a project.Thanks for quick reply! I am paralyzed and car is in garage I will have to have someone park so I can get around both sides.It’s my every day driver till we get snow.
Good to hear that you have a bi directional scan tool to at least turn the fans on…the “inputs” for operation are ECT and AC Pressure Sensor…I believe 236 degrees ECT temp is the magic number for the high speed fans to come on but unfortunately the PCM doesn’t look at temperature…it looks at voltage…you can take the ECT sensor out and measure the resistance vs temperature chart and see how accurate yours is…also if you remove the ECT connector and jump both terminals together (it is a thermistor circuit and you won’t damage anything) and start the car the ECT will read 284 degrees on your scan tool and the fans will be on high speed…if they come on electrically everything is working in your fan circuit…when you remove and reinstall the connector you will get a P0115 and P0118…just erase them !!…I’ve also come to find out that the AC pressure sensor also controls the fans and you can see the pressure and voltage with your scan tool…I don’t have the sensor pressure turn on and offs for fan operation…with a Snap On scan tool you can find the AC Pressure Sensor data PIDS under “engine, “data display”, Acc/Elec/Theft data.
My apologies for stiching table together but could not get on one page and be readable.
Fan #1 = both fans low speed.
Fan #2 = both fans high speed
Fan #1 or relay 45 energizes at 226deg, with a/c on at 185deg or 219psi below 30mph. Relay 45 will de-energize at 219deg or 180psi or above 35mph.
Fan #2 or relays 43 and 44 {relay 45 is still on} will energize at 235deg, with a/c on 255psi. Relays 43 and 44 will de-energize at 226deg or 219psi or 90mph.
Run on temperature; above 284deg triggers fan #1 {relay 45} for 1 second after car has been shut off.
Last edited by purrvert; Sep 15, 2021 at 02:33 PM.
Thanks for all the replies I looked into a little today. I need to spend a little more time with scanner on it to see what is going on. I couldn’t get hot enough today only got to 221 f.
Here is the settings in my stock 2000 Coupe , screendump from my HP Tuner VCM Editor
I notice you have not selected Series/Parallel in the Hardware column. Can you make the change? I'am curious if saving that change will move Ignition Off column to Fan 1 {First Stage} column.
The PCM ground C1:42 when temperature on ECT rise above 226F and ground the C2:33 when temperature on ECT rise above 235F and energizing the relays shown above .
The number of fans and how the are connected is a result of the wiring/relays outside of the PCM
How hot is it before worrying about creating engine problems with these? I know run hot and design to but close to 240 degrees seems hot.
From your original post "Ican read 236 degrees on dash and still doesnt come on but car will cool off till around 220 without it.Any help is greatly appreciated!" The car appears to be cooling back to 220. But by 240 [at 235deg] your high speed fans should be running and temperature should drop. Bear in mind you've probably lost some cooling efficiency with debris inside and outside radiator slowing down the cooling process. Appears to me your C5 seems to be operating normally.
High speed fan
