: cooling fan not working



linopizzolanti
01-19-08, 03:13 PM
I have a 98 cadlllac catera that the engine cooling fan does not activate at the activation temperature. I know the fan is working because I was able to jump the wires in the fuse box, but I am not having any luck finding the problem. Any help would be greatly appreciated. Ps. Can the fan problem cause an o2 sensor problem? I have a p0133 code and a p0154 code coming up also. Thanks.

frank moran
01-19-08, 05:19 PM
as a suggestion there are two coolent temp switchs on the left rad tank that control the fans, one is for high temp the other for lower temp, check the lower first, i think this is the low temp switch. The swithes act to complete the fan circuit, when the coolent temp drops the switch opens shutting off the fan, very similar to your house thermostat. First check the connections on your O2 sensors, i belive it is the front ones on each bank.

linopizzolanti
01-19-08, 09:57 PM
Thank you. How do I know if the switches are good or bad?

frank moran
01-19-08, 11:20 PM
Thank you. How do I know if the switches are good or bad?

We are assuming it is the primary fan which is the problem. I looked at a schematic and the process to check the fan out is complex, however you confirmed the fan works. Looking at the diagram the top rad sensor which is the primary fan control, a quick and dirty method may be to bring the engine up to temp where the fan should kick on, this is over 212 degree's, disconnect the top sensor wire harness and jumper the brown and blue wire to the black wire or just jump brn and bl to any ground., that should kick the fan on, if it does it tells us the sensor (or the wiring) is bad), first rule out the sensor. To go furthur you will need a wire diagram. The primary fan comes on at 212 and goes off at 203. As a back up If it gets above 239 the secondery fan will kick on and kick off at 248. If you get nervous during the high temps kick the AC on and that will kick the condensor fans on. Hope this helps. This is a complex and relay loaded system....

linopizzolanti
01-19-08, 11:33 PM
Thank. Will try tomorrow morning

linopizzolanti
01-20-08, 11:44 AM
Are both switches in the radiator, one top and one bootom, screwed in?

frank moran
01-20-08, 12:09 PM
yes they are.

linopizzolanti
01-20-08, 10:37 PM
Hi Frank:
I disconnected the top temp. control switch and jumped the brown and white wire with the black and the fan kicked on. There are three wires. One is brown and blue, the other is brown and white, and the last is black. Would this indicate that the temp. control switch is bad? Thanks for your help.

frank moran
01-21-08, 09:14 AM
Hi Frank:
I disconnected the top temp. control switch and jumped the brown and white wire with the black and the fan kicked on. There are three wires. One is brown and blue, the other is brown and white, and the last is black. Would this indicate that the temp. control switch is bad? Thanks for your help.

I would say yes, you confirned the fan works and all the wire circuits and you started at the source which is the coolent temp. One question , are you sure the fan is not kicking on as designed? the temp needle has to be above the mid point for the fan to come on (AC off) otherwise put a sensor in. I think they are cheap.

linopizzolanti
01-21-08, 09:26 AM
Yes I am sure the fan does not kick on. I have seen it go past the mid point and it doesn't kick on. I saw the sensor on sale at Rockauto for $13. Thanks . Now my other problems with my O2 sensors. I will be working on those today. Thanks for all your help.

Resilient
01-22-08, 12:40 PM
I am guessing you already checked but in case... verifiy the condition of the fuses... See my other recent posts... I had a similar problem (overheating and the aux. cooling fans were not coming on)... ended up noticing there are 3 fuses for the aux. cooling fans...

Using the owner's manual, you'll see there are 2 other aux. cooling fan fuses (30amps)... under the cable that goes to the ECM... 79 cents a fuse, it's worth a look...

I had one fuse burnt, which haoppen to be one under that cable (you have to pull out the ECM (computer) from the fuse -relais box in the engine bay to see the fuses... or else they will go un-noticed.

linopizzolanti
01-22-08, 02:14 PM
Thanks. Will check.

linopizzolanti
01-22-08, 02:36 PM
You were right! There is a 30 amp fuse under the powercord and it was blown. So what you are saying is that fuse might be the problem to my fan not working? I will replace it and test it. I will let you know what happens. Thanks.

linopizzolanti
01-22-08, 05:32 PM
You were right!!!!!! That one fuse, under the harness is what was causing the fan not to turn on. I changed the burned out fuse and now it works. I still am having problems with my o2 sensors. My check engine light is on. I had codes of p0133 and p0154. I changed the sensors with two universal ones but I think I am going to have to go the OEM way. Any ideas? Thanks for your input. It saved me a lot of time and money trying to change the coolant temperature sensor.

Resilient
01-24-08, 11:19 AM
Great...

As for the Codes, after replacing the O2 sensors (not sure about this), but you might have to get the codes reset, then see if they come back... I believe the codes stay resident in memory until cleared, then fix the problem...

linopizzolanti
01-24-08, 12:29 PM
I did get them reset but they came back on. the same codes.