I have an 86 iroc with a 305 tpi and it has a single cooling fan that runs continuously. I unplugged all the a/c sensors. I ohmed out the relay and it checks out ok. I've replaced the fan switch below the throttle body. I put an ecm in it but it still stays running. I can't find any shorts. Thoughts?

 

With the key on check the relay for proper operation. With the fan on you should be able to unplug it and hear it click. Then reconnect and if clicks right away you have a 12V short on the low current supply side (relay coil is energized at all times, closing the switch on the high current side). If it doesn't click but the fan comes on you have a 12V short on the high current supply side. If it's the low current side work backwards from the relay plug to find the crossed circuit and isolate. If it's on the high current side work backwards from the fan to find the crossed circuit and isolate.

 

I'm curious, how many ohms should I be seeing when the pcm grounds the relay? .2 or so.

 

Update; I missed the low pressure cut-off switch when I was unplugging the rest of the a/c items. Unplugged it, the fan turned off. Derrr

 

The fan switch isn't below the relay, it should be in the passenger head for a single fan. The switch in water neck is for the ECM to read coolant temp. The sensor in the driver head is for your temp gauge reading.

 

low pressure cut off switch shouldn't have anything to do with the fans continuously running...weird.

 

Well I replaced the switch but it didn't fix it. Every time I unplug it, it turns off. Every schematic and description and operation on all-data, contradicts itself. I'm at a loss now. I don't have a Tech1 to scan it either. The ECM is definitely grounding the relay. Why? I don't know. Things I've checked: Control head is properly grounded. Refrigerant level ok, relay not shorted, wiring to fan not shorted, replaced coolant temp sensor under TB, wiring to sensor checked out ok. I replaced the ecm, still turns on. It has a hyperchip in it, maybe that went bad??? I don't have a switch in the head between the #6 & 8 plug like I've read everywhere else. All data says its in the a/c line and the schematic agees b/c the wiring that goes to the sensor is spot on.