smeds

iTrader: (1)

Hello everyone, so I have been at it for a few days now trying to debunk why my dual fans are not turning on in my 1986 IROC-Z28. The engine is a 350 L98 completely swapped from a 1988 Corvette along with the harness and ECM.
Through research I've learned that with dual fans such as I have, signals for the fans to kick on come from the CTS (coolant temp sensor) for the (primary) driver side fan, and the fan switch in between the 6 & 8 cylinder heads on the passenger side controls the aux fan.
Initially suspecting a relay I replaced both and let the car get up to 230 degrees but got no fans. I've also run the A/C in the car and gotten no fans. I did run 12V to the A port on both relays and both fans kicked on just fine proving they work but showing me no signal is being received. Using a volt meter I tested continuity within all the circuits (CTS to relay, fan switch to relay, ECM to relay/CTS) and all connections are good. However when I connect to the CTS in the block and the relay I get very intermittent continuity and when connected from fan switch to relay I get nothing.

Would the fan switch only work with freon in the system? Also I'm wondering if my CTS and/or fan switch is bad? Thanks for any help.

henryd3

iTrader: (128)

Fan switch has nothing to do with freon. It's in the water jacket and produces a ground to the relay which activates said relay and turns on the fan. Sound like the wires to the relays are faulty or their connections aren't good. With the key on, grounding the green with white stripe wire going to the fan switch should turn on the pass side fan. If that works but the fan switch won't turn it on then suspect the switch. Check the technical articles section for fan system info

smeds

iTrader: (1)

Thank you, I was able to ground the green/white wire and had the fan come on. In my diagnosis I traced all wires from the relays to the ECM and found that the tan/wht wire in position D runs to the C207 connector and not the ECM.
I have pinouts for 1985 and 1987 Camaro C207 connectors, but I have a 1988 Corvette harness in the car from my engine swap. Not all of the wires match up in that connection to the 1986 IROC wires which tells me I need a pinout for the 1988 Corvette C207 but I am having a hard time finding one.

smeds

iTrader: (1)

Here is the C207 in my car from the 1988 corvette. I need to verify each wire to ensure they plug into the correct location on the 1986 IROC side of the connector. Thanks for all help.

greenyone

iTrader: (1)

So my understanding of the TPI dual fan cooling system is as such:



The driver’s side fan operation is governed by the ECM which takes it’s reading from the coolant temp sensor/sender located on the intake manifold under the throttle body.

The driver’s side fan is also governed by one of the switches on the air conditioning system (if equipped).

The passenger side fan is governed by a fan switch located near the back of the engine on the passenger side.



Is this correct?



If so, then what is function the sender/switch on the front drivers side of the engine? Or does this switch/sender actually operate the driver’s side fan?

JamesG1986

Hello I just bought my first car, it's a 1986 camaro 305 with a 4 barrel carb on it. It a base model, nothing special. It overheats and the cooling fan won't come on I don't want to jerry rig it in any way, I just want to change the sensor that could possibly be bad. I changed the fan blower relay by the brake booster and I also changed a sensor on the passenger head near the oil dipstick it is connected to a green wire and it still won't come on, the fan works if I turn the A/C on, I let it heat up to about 220 then I kick it on but it won't come on automatically if I jump out the A/C fan relay it will kick on. I see another sensor on the drivers side head I'm not sure what it's for or what it does, I'm stuck and don't know what else to changed. Please help me I'm open to any suggestions. Thank you

greenyone

iTrader: (1)

Try this. Unplug the wire from the fan switch (passenger side by the dipstick). Get yourself a piece of wire long enough to connect that green wire to either some bare metal on the body or directly to the negative lead on the battery. If the fan comes on when you ground out that wire then the fan switch/sensor is faulty. If it does not come on then you have a wiring problem. You should be able to do this with the ignition on but the engine does not have to be running.

I think the sensor on the passenger side is just the sending unit for the gauge.

Ozz1967

iTrader: (4)

The sensor on the drivers side IS for the temperature gauge in the car. the sesor on the passenger side is for the fans(s)

I would suggest that if grounding the wire as posted above doesn't work, then you have a relay issue because the fan's work when the AC is turned on, which tells me the "circuit" is good.

Also, don't put too much teflon tape on your switch when you install it, it can cause an issue where the switch won't make good contact with the block (required for the ground signal to activate the relay) and thus, no switching is happening.

Ron U.S.M.C.

As mentioned above, if you ground the wire going to the stock switch on the passenger side and the fan comes on, then you're in business. You now have the opportunity to install a temp. controlled, adjustable fan switch.
With this switch and a 180* thermostat you can keep your car running at IMO more reasonable temps. like 180*to 200*range assuming your car does not have any other issues.

It takes only $20.00 and a few minutes of your time.

Here's what the circuit looks like and the switch necessary.
The switch is universal and you do not use the diagram included. New diagrams that I provide are best.

This one is the simplest but others are available for high amp fans/etc.
I have been running two independent circuits using two of these switches with relays.
I run black wire loom on all wires including the probe wire and paint the controller and mounting bracket black and you can either hide it or leave it exposed as I have.

Anyway, its just another option that comes with PM help if necessary.

Switch with part # 733653 = http://www.autozone.com/cooling-and-...67187_69565_0/