RWD - Details on adding a GM electric fan, relays, and wiring.

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Details on adding a GM electric fan, relays, and wiring. 200

I can assist you with the wiring details of adding an electric fan and using the GM factory relays/sensors. I'll use my '86 Pontiac 6000, 4-cylinder engine as an example.

First off, the radiator fan has only 2 wires going to it (Black w/Red-Stripe is +12 volts, and Solid-Black is ground). Follow the Black/Red wire back to the fan relay, on my car this is mounted on the side of the driver's strut housing, about 4 inches from the transmission.

The relay is a 2"x1"x1" black square block (markings on case: 10038311 6057 TRW Z-8247 USA) and it has 4 wires going into it. I've listed the wires below:

Red: Main power (+12 volts, fused from battery)
Black w/Red-Stripe: Power sent to Fan (+12 volts when turned on)
Brown w/White-Stripe: AC signal line (turns on relay when AC is on)
Green w/White-Stripe: Thermal switch signal line for cooling system

On my car, the thermal switch to turn on the fan is a brass sensor screwed into the Head, just below the #4 spark plug (points straight out towards the front of the car). Looking at the engine block below, it's mounted just above the stamp: "2.5L GM" The thermal switch is basically an ON/OFF gate that shorts the signal wire to ground when the coolant temperature rises above 235 degrees F. For reference, my thermostat starts to open around 195, is fully open by 210, and the "TEMP" idiot light comes on at 260. (boil over occurs at 265-270 assuming 50/50 coolant and proper functioning radiator cap) In many 6-cylinder engines, you will find this sensor mounted in the radiator.

The AC signal line is basically wire that carries the signal that tells the relay when you've turned the Air Conditioning on. If I remember correctly, the AC system grounds the signal line to activate the relay. You should be able to wire this to the AC switch on your center console. Find some wire that becomes grounded when the switch is in the "ON" position.

I'm in the process of trying to find out how to wire up a Chrysler timer relay to the AC signal line. In many '80s Chrysler cars, the radiator fan will turn on for about 3 minutes after you turn off the car. This could seriously benefit many Turbo Volvos out there (or cars in warmer climates) in cooling the engine after being shut down. This "shutdown-cooling" would also help decrease the engine compartment temps which have a tendancy to bake wiring harnesses, belts, hoses, and anything nylon. I'll post more information when I've finished my research.

Remember, when adding wiring to the GM system always use the same or a heavier gauge of wire. Don't use 22 gauge wire where a 14 gauge wire is needed, -or you'll have an electrical fire on your hands. Fuse your power to the battery and enjoy the cooling.

Lastly, a bit of misc information. There are 3 temperature sensors on this car. The thermal switch for the radiator fan that I mentioned above, another on the top of the Head pointing upwards (Green wire, Idiot Light signal), and the 3rd is in the aluminum thermostat housing (has two wires, Yellow and Black, and is the temp signal for the fuel injection computer).

God bless,
Fitz Fitzgerald.

P.S. After talking to the Volvo mechanics at my local dealership, I re-installed the factory fan back in the car. While it does run all the time, it keeps the engine bay temperatures down and helps the longevity of the wiring harness, plastic, and rubber parts. This coming summer, I hope to install a small pusher fan in front of the radiator with the Chrysler timer circuit, along with the basic Thermal-Switch and AC signal inputs.
'87 Blue 245, NA 225K


New Installing Electric Fan(PLease help im am buying on Saturday!!!) [200]
posted by  I have a volvo  on Thu Oct 2 08:51 CST 2003 >

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