Radiator fan no worky...

[Styluss]

Yup, the icing on the cake with the car lately is that the radiator fan won't come on. Even at near max temps. Yes, the temp gauge still works. I think. It will be at near max temp, but there are no signs of distress under the hood. And once I start to drive the car, the temp gauge dips to about the 1/4 mark. And this is within like a block of slow driving... I don't get it.

Thoughts?? I would really like to not explode one the way to Indy.

[Barry]

Jump the relay manually to test the fan motor. If fan motor is good, make sure relay is good. If relay is good then it is a cts/ecm issue.

[Styluss]

Easiest way to jump the relay?

[Barry]

Take the relay off and put a paperclip in the socket to bypass it. Just make sure your jumping the correct wires.

[DTMAce]

I thought if you disconnected the fan temp sensor, the fan would automatically kick in? That and/or ran the A/C?

[SuzukiGhostRider]

It will Ace. On both counts. So will disconnecting the TPS sensor. ANY of these will trip the fan automatically. If it does not, then you can likely assume it's the relay. However if unsure on the relay , jumping the fan directly off of the battery is the fastest way to tell if the fan motor is any good. Can't really screw that up, only two wires coming off of the fan.

So, jump your fan. If it comes on it's good. Then unplug your CTS or TPS and if the fan doesn't come on, you know the relay is screwed.

[pghturbo88]

Styluss, apologies if I am overstating obvious known concepts. Recall that there are two temp sensors, one for the gauge and one for the ECM. If your car is OBD I, an easy and quick way to test the fan is to insert the paper clip into the proper pins of the diagnostic connector, and turn the key to ON (but not start). This fires ECM outputs (cooling fan relay included), so as soon as you turn the key on, you should hear the fan run. To me, this is a more comprehensive test than simply jumping out the fan relay, as you are verifying the integrity of the ECM output, fan relay, and wiring to the fan. If this test does not start the fan, start at the fuse and work your way along the circuit testing for 12 VDC. If you make it all the way to the fan motor connector, and see 12 VDC on the pigtail, then you probably have a bad fan motor. With the wiring pigtail still disconnected, switch your meter to the ohms scale, and put your leads on the fan motor -- you should see a "reasonable" ohmic value (not 0.0 ohms or meg (millions of) ohms).

If the paper clip trick starts the fan, then you most likely have a bad ECM temp sensor. Oh, and a quick clarification regarding running the A/C to start the fan, this only works once the pressure switch up by the radiator cap (on my 89 2.8L) trips, which won't happen if you are low on charge.

[Chad91GTZ]

Might have something to do with all that mud! Good luck Ryan

[SuzukiGhostRider]

Yes, there are a hundred ways to make the fan kick on and jumping the tester pins is yet another good way. What did you find out?

[Styluss]

The ground wire was completely split in half at the firewall. Not cool.