Main coolant fan not working

[pauleyman]

Ok I'm stumped. Ac fan works as it should. I tested every relay by swapping to ac slot so all the relays are good. Jumpered main fan (lo) and (hi) under the relay and it comes on so fan is good and wiring to fan is good. Scan tool reads coolant temp fine so sensor and harness are good. Temp hits 200 plus and fan never comes on. It overheated yesterday. Only thing left is wiring to relay to trigger it and ecu i think. Maybe a ground somewhere? This is all after a head swap. Several days after head swap it popped a radiator but that was probably because it was overheating and son didnt notice. Bring on the suggestions before I tear apart something unnecessarily.

 

[19Eclipse90]

Grounds are fine else the fans wouldn’t work when the relays were bypassed. Grounds 1 and 3.

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Power side for the radiator Hi and Lo relay coils shares common with the condenser fan Hi relay. Since these are all in the relay box, I expect they should be fine.

The grounding side of the radiator Lo relay goes to ECU pin 21. The grounding side of the radiator Hi and condenser Hi relays goes to ECU pin 20. You can check continuity across those to the ECU if you want to be thorough. I’d check the contacts in the fuse box itself to make sure they are clean and haven’t pushed down into the fuse box.

So, you tried both radiator relays in both condenser relay slots? And verified the condenser fan goes both high and lo?

I doubt you undid connector A-32 for a cylinder head job, front and engine control harness combination, but double check that connection and the wires are all seated properly.

I think I have a spare ECU if you wanted to try that.

 

[1990TSIAWDTALON]

Crossing my fingers it is just a bad connection but with that fan not working on low or high, sure seems to point back to what triggers them Paul.

 

[pauleyman]

Grounds are fine else the fans wouldn’t work when the relays were bypassed. Grounds 1 and 3.

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Power side for the radiator Hi and Lo relay coils shares common with the condenser fan Hi relay. Since these are all in the relay box, I expect they should be fine.The grounding side of the radiator Lo relay goes to ECU pin 21. The grounding side of the radiator Hi and condenser Hi relays goes to ECU pin 20. You can check continuity across those to the ECU if you want to be thorough. I’d check the contacts in the fuse box itself to make sure they are clean and haven’t pushed down into the fuse box.So, you tried both radiator relays in both condenser relay slots? And verified the condenser fan goes both high and lo?I doubt you undid connector A-32 for a cylinder head job, front and engine control harness combination, but double check that connection and the wires are all seated properly.I think I have a spare ECU if you wanted to try that.

I did not check AC high as you can't unless you're coolant temp is high. I did all tests with cold car.

 

[pauleyman]

Update. I didn't feel like chasing wires so I bypassed the factory relay and ran a new one off a switched 12v so the fan is on all the time now. Not optimal but the car can be driven. When it cools down I'll swap ECU with my ECMlink ECU. If I'm correct there are only two possibilities. I'll trip the fans with ECMlink. If it doesn't fire the wiring from ECU to relay is bad. If it fires the original ECU is bad. If anybody knows any other possibilities I'm all ears. I would think the code uses temperature as the main on off. TPS, VSS etc are only used to go hi or lo. One more thing. I ran it for 10 min or more, lower radiator hose never got warm. Thermostat is 2 years old.
Technical manual page.

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[1990TSIAWDTALON]

Paul, double check your tuning. The radiator on/off spots. Just to be sure something isn't out of range or such. I'm not very familiar with the 2g settings so I may not make any sense.

 

[pauleyman]

Well there is no tuning. This is a stock ECU. Only reason I will put in the ECMlink ECU is to rule out both the wiring and ECU itself.

 

[1990TSIAWDTALON]

Ok, got ya!

 

[Vladimir]

All of this happening after the head swap, makes me question if your system is air locked especially after the radiator blew up. I think chances of ECU going bad are very slim. It is possible but slim.

You said you confirmed with the scanner that your temp sensor is reading, but was the engine already warmed up and at full operating temp, or you just looked that it's reading and after you drove the car looking at the temp gauge that reads from a different sensor on the thermostat housing?

Chances are the gauge would read high because the little sensor that is also close to the main coolant temp sensor gets hot, it's shorter and it changes resistance value quick enough for the gauge to go up and down.

While the coolant temp sensor that that communicates to the ECU itself is airlocked and not telling the ECU to trigger the Fan cause it never really reaches operating temperatures due to not being submerged or lack of circulation.

Did you bleed your car with the nose jacked up, radiator cap off and the heater running? Did both hoses for the radiator got hot? If the thermostat is not opening or the car is not bled properly it will build extreme pressures and cause airlocks as well.

If the thermostat never opened after the head swap and the system never circulated properly, thermostat housing could be airlocked, since technically it's the highest point of the cooling system.

I would take out the sensor or use a spare sensor, put it in a pot and cook it with a thermometer, while it's plugged in ignition ON, if the fan goes on, that would confirm airlock.

I've seen so many cars over the years melt engines just to hear the owner saying the fans never came ON etc... I've witnessed it myself as well.

 

[pauleyman]

All of this happening after the head swap, makes me question if your system is air locked especially after the radiator blew up. I think chances of ECU going bad are very slim. It is possible but slim.

You said you confirmed with the scanner that your temp sensor is reading, but was the engine already warmed up and at full operating temp, or you just looked that it's reading and after you drove the car looking at the temp gauge that reads from a different sensor on the thermostat housing?

Chances are the gauge would read high because the little sensor that is also close to the main coolant temp sensor gets hot, it's shorter and it changes resistance value quick enough for the gauge to go up and down.

While the coolant temp sensor that that communicates to the ECU itself is airlocked and not telling the ECU to trigger the Fan cause it never really reaches operating temperatures due to not being submerged or lack of circulation.

Did you bleed your car with the nose jacked up, radiator cap off and the heater running? Did both hoses for the radiator got hot? If the thermostat is not opening or the car is not bled properly it will build extreme pressures and cause airlocks as well.

If the thermostat never opened after the head swap and the system never circulated properly, thermostat housing could be airlocked, since technically it's the highest point of the cooling system.

I would take out the sensor or use a spare sensor, put it in a pot and cook it with a thermometer, while it's plugged in ignition ON, if the fan goes on, that would confirm airlock.

I've seen so many cars over the years melt engines just to hear the owner saying the fans never came ON etc... I've witnessed it myself as well.

All good points. I bled with a coolant funnel nose in the air. I know how to do this. I read the temp through the ecu from cold and watched it warm up to op temp. I think im on the right track. Thermostat may stil have problems and I may still change it just because but that doesnt explain the fan.

 

[Vladimir]

All good points. I bled with a coolant funnel nose in the air. I know how to do this. I read the temp through the ecu from cold and watched it warm up to op temp. I think im on the right track. Thermostat may stil have problems and I may still change it just because but that doesnt explain the fan.

Yes. If the temperature was taken from live data and it showed over 200f+ the Fan should have turned ON, agreed.

Edit: I would probably wait a little longer, probably until 220 or so it just depends. Fans turn on above thermostat operating temp, not with

 

[luv2rallye]

Here's when the 2g fans are designed to turn on: https://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/

 

[pauleyman]

Here's when the 2g fans are designed to turn on: https://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/

Thanks.
I dont know why I didnt think about it but I could probe the wire at ecu to see if I get an output voltage.
Also might put a potentiometer in place of the coolant sensor to test the car engine off and cold.

 

[luv2rallye]

Also might put a potentiometer in place of the coolant sensor to test the car engine off and cold.

- Or just short the engine 2 wire coolant temp sensor (for engine hot) and unplug it (for engine cold).
- You do know the wiring diagram in post 5 is for a 1g, right? The 2g is different.
- On a 2g, AC on/off and VSS also play a part in which fans go on (see post 12 link).

 

[pauleyman]

- Or just short the engine 2 wire coolant temp sensor (for engine hot) and unplug it (for engine cold).
- You do know the wiring diagram in post 5 is for a 1g, right? The 2g is different.
- On a 2g, AC on/off and VSS also play a part in which fans go on (see post 12 link).

I didnt think you could just short it for the temp sensor.
Concerning post 5 I knew it looked weird and I suspected it was for a 1g but this was copied straight from the 2g tech manual.

 

[pauleyman]

Update. I let it get to temp again and thermostat opened. Both hoses are moving coolant and hot as they should be. Son will probably drive it tomorrow. Im guessing with ambient temps in the low 80s and a bone stock car it might run a little cold with fan on all the time.

 

[luv2rallye]

Concerning post 5 I knew it looked weird and I suspected it was for a 1g but this was copied straight from the 2g tech manual.

On which page? I don't see it.

Also did you burp the lower radiator hose with rad cap off to bleed? Take off the radiator cap, gently squeeze the lower radiator hose, put the palm of your hand over the filler hole, release the hose, remove your hand, repeat. And of course make sure the bleed hole in the thermostat is at the top of the housing when installed.

BTW here's the cooling system wiring for the 97-99:

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[pauleyman]

On which page? I don't see it.

Also did you burp the lower radiator hose with rad cap off to bleed? Take off the radiator cap, gently squeeze the lower radiator hose, put the palm of your hand over the filler hole, release the hose, remove your hand, repeat. And of course make sure the bleed hole in the thermostat is at the top of the housing when installed.

BTW here's the cooling system wiring for the 97-99:

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I bled while running with a coolant funnel. Same thermostat is in place. I didnt remove it for this job.
The tech page from.post 5 came from here.

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I am working on my 95 not my 97.

 

[luv2rallye]

Oh, so the 2ga has different fan wiring than the 2gb? I didn't realize that as I only have the 1999 Eclipse Service manual.

 

[19Eclipse90]

Here’s the diagram from the ‘96 manual which should be comparable to the ‘95. Unless I’m missing something, these appear the same as 2Gb.

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[luv2rallye]

Yes that is the same as my 99, but totally different than the 95 shown in your tech manual p. 1-76. So is the 95 the same as the 96-99 or is it like the tech manual which is different? Notice the tech manual shows 3 wires going to the condenser fan motor.

 

[19Eclipse90]

I don’t have V2 (which includes the electrical) of the ‘95 FSM, but these are from volume 1.

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[luv2rallye]

Ya without V2 of the 95 FSM that doesn't answer the question.

 

[19Eclipse90]

Even though both the radiator fan and condenser fan connectors show 4 wires per connector rather than 3, like in tech manual shown in post 5?

 

[pauleyman]

Oh, so the 2ga has different fan wiring than the 2gb? I didn't realize that as I only have the 1999 Eclipse Service manual.

No. What I'm saying is I think the 2g tech manual is wrong and has 1g stuff in it.

Even though both the radiator fan and condenser fan connectors show 4 wires per connector rather than 3, like in tech manual shown in post 5?

I'm honestly not sure