Jcase350

Both fans quit working on my Iroc. Fuse is good. Is there a fan relay? Where? I don't think both fans would go out at the same time. Anything else to check? Thanks

thunderstick

both fans are operated independently. one by fan switch in the head, comes on at about 237* and the other is controlled by the ecm if you have the a/c system on. the relays for both are on the driver side firewall. the third one you'll see is for the fuel pump. do you know for sure they both do not work?

Jcase350

When I drove it yesterday, it was running cool while actually driving but when I would stop and idle it would heat up pretty quick to almost overheating. I stopped and popped the hood and neither fan was running. Are all three relays the same? How do I tell which is which and does that relay control both or like you said do they run independently with separate relays?

camaronewbie

seperate relays for each fan. wiring diags will help you pick wire colors for fans vs. fp: http://www.austinthirdgen.org/index.php?pid=19

camaronewbie

Oh - also ... the primary fan like mentioned is controlled by the computer - the computer gets it's input from the Coolant Temp Sensor, located on the intake close to the thermostat - has 2 wires, black and yellow.

Secondary fan is controlled by the fan switch - it's located in the pass side head - has a mushroom looking connector on it. If by chance the wire connector for that fan switch it bad, broken, etc. ... most any local parts store can order for you a Dorman part# 85140 - that's the connector/pigtail.

Jcase350

Any way to actually test those relays?

camaronewbie

For the secondary fan, can test relay by grounding the wire to that fan switch in pass side head - should hear the relay click (or hold hand around it and feel it click).

NOt sure if the factory relays are marked or not - some are - but each terminal on a relay (if it's marked) has the same numbers ... 85, 86, 87, 87a, 30

85 or 86 will be ground, the other will be 12v+ - those two wires "activate" the coil inside the relay, which creates a magnetic field and literally moves a lever magnetically from one position to the other.

30 is battery 12v+ always, regardless of anything else

87a is the "resting" spot of the lever - when relay not activated the lever rests on 87a

87 is the "activated" spot for the lever - when relay activated lever moves from 87a to 87

So, when relay is at "rest", the 12v+ from terminal 30 connects through the lever to terminal 87a - in this "off" state, 85 or 86 will have ground, the other will have nothing, 30 will have 12v+ from battery, and 87a will have 12v+ from the lever connected to 30.

When relay is activated, 85 or 86 will have ground, the other will have 12v+, 30 will have battery 12v+, 87a will have nothing (because the lever moved to 87), and now 87 will get the 12v+ from 30 because the lever moved.

When the relay is activated, the lever moving will make a click sound (or you can feel it 'click'). Make sense?

TampaTim

Rather than starting a new thread...Passenger side coolant sensor in the cylinder head.My connector is no where to be found.Can someone direct me as to where it originates from and how it should be routed to the sensor.Thanks.. 88 iroc-z 350 tpi.