My radiator cooling fan isn't working, can't figure out!

[jblackburn]

Engine coolant temperature sensor

[tjts1]

Install a manual overide. Every vehicle I have owned over over ten years old I have installed a manual overide. That way you leave nothing to chance. Not a difficult procedure.

Totally agree. Mine runs off a spare foglight switch.

[holler1]

The Engine Control Module (ECM) is what is connected to the fan relay. ECM reads the high pressure sensor on high side a/c line and the ECT sensor. The ECM will run the fan at either speed as the condition warrants.
Given ECT below 220 the a/c pressure reaching 175 +/- triggers fan to run on lo. If pressure goes above 240 +/- with lo fan then fan will be switched to hi.
With no A/C the fan will run lo at 220 +/- and if coolant temp reaches 240+/- it is switched to hi.
With a/c on and fan running already on lo and ECT goes to 220 +/- then fan goes to hi
Usually due to radiator overcapacity (at least by old RWD engine driven fan standards) the fan running on low for a/c purposes is keeping coolant temp below 200 even in 100 degree weather and the ECM is not running fan for ECT concerns.

I checked my fan just now. Without AC, the low speed fan came on at 217 F, and went back off when the temp went down to about 205 F. I had to run the engine up to 1800 rpm to get to heat up that much. My hand holding the throttle open got too hot to run it up to 240 F to see if the high speed fan would come on. With the AC on, the low speed fan stays on all the time. With AC on, I ran the engine up to 2000 rpm for a few minutes and the temp didn't go above around 200 since the low speed fan was on.

Conclusion - The system seems to be working OK, although these control temps seem kinda high to me, with the thermostat set at 188. The low speed fan with AC on seems to do a good job of keeping temps below 200, as jimmy57 indicated. So I guess I'll stop worrying (about this anyway, I always have something to worry about).

[fiore67]

Can someone tell me which wires i should hook up to a battery to test my cooling fan. I swapped a working relay with mine and my fan doesn't come on either with the AC or any other time. The 3 wires to the fan are red, green and black. The car is a 95 850. Thanks

[jt74]

Hello... hope you all find yourselves well.

I just changed out my radiator and nothing is leaking. At this point I have changed every major part of the cooling systems. New waterpump, radiator, thermostat, expansion tank, cap, thermostat and hoses. Seems to be ok except sometime during the swap, I must have pulled on the middle ( power in I believe) connector to the cooling fan relay. I took her out for a good drive and it started to over heat after about 15 miles. The fan did not come on at all.

I jiggled the wire and the fan clicked on for a second then shut off again. I then pushed the leads (yellow/yellow and white wires) a good ways into the connector and the fan came on and stayed on until it cooled the engine enough to turn off. I checked that the connections were good by turning on the AC and it worked fine.

While I was waiting for the motor to cool I disconnected the switch. The wire on the bottom or back side was in good shape. The actual wires ( yellow/yellow and white) were loose and the plastic or whatever surrounds the leads were pretty corroded and the yellow/white lead was clogged with that yellowish crap inside the connector.

I have looked around for the connector but everyone seems to only sell the actual relay switch itself, not the connectors. Any ideas of what I can do to either salvage the current connector or maybe where to get a new one and splice/solder? Any ideas or comments would be greatly appreciated. Thanks a whole heap.

[gilhuly]

You should be able to take apart the one you have and clean it up and add new metal guts if you choose. You should be able to pull the metal innards out after hammering a couple paper clips flat and using them in the back side of the connector to release the barb fitting which holds the metal in the plastic connector on each side of each pin (sides, not top and bottom). I'd just try shooting a bunch of contact cleaner in there first and see how it goes, but what I've described is pretty easy once you understand what's going on.

[jt74]

Thanks gilhuly. I cleaned it out pretty good but the guts inside of the connector were really corroded and made of some plastic material. I ended up taking most of it out. The leads are in great shape so I cleaned them up good and put some dielectric gel all over them and pushed them all the way out of the connector. They went on pretty snug to the male ends of the relay and then I just clicked the plastic connector up over them. Fan is working as it's supposed to now.

On this last drive I found out the lower radiator hose was not on as far as it should be so letting her cool down now and will get it on there good. Tomorrow will be the big test, driving over the hill and sitting in rush hour traffic in the afternoon. Wish me luck!!!!

[Ozark Lee]

Can someone tell me which wires i should hook up to a battery to test my cooling fan. I swapped a working relay with mine and my fan doesn't come on either with the AC or any other time. The 3 wires to the fan are red, green and black. The car is a 95 850. Thanks

The black wire goes to the negative post. Individually wire the positive post to the either the red wire or the green wire. I can't remember which is high speed and which is low speed but you should be able to hear the difference in fan speed. Don't wire the positive wire to both the red and the green at the same time.

...Lee

[fiore67]

Looks like the fan is toast. Motor was seized. tried to free it up to no avail. time to replace

[Ozark Lee]

Good thing you caught that now. We had another member that had the fan catch on fire in his parking lot at work. His car burned as did the cars of the people next to him before the fire department got there.

...Lee