For some time I've wanted to convert to dual electric fans, but I didn't want to be inconvenienced by various in-cabin manual switches. My desire was that the fans switch on automatically. The following idea is from AndyZ28 who, members may recall, was one of the first to develop the 1LE brake conversion (more about that can be found on his CD, www.andyz28.com).

How's It Work?

According to Andy, any time a parameter is met, coolant temperature or A/C pressure, the controlling switch grounds the relays turning both fans on. The fact that the switches are "making ground" permits control with very little current flow through the switch(s), as opposed to controlling the relays with the "ign."

Parts Required (I generally bought new, but many of the following parts can be picked up cheaply in a boneyard):

Fans - Stock GM.

Motors – CarQuest 209089.

Motor Wiring Harness/Pigtails – CarQuest S568.

A/C High-Pressure Switch – GM 14089590 (NO, Normally Open).

A/C High-Pressure Switch Harness/Pigtails – GM 12085521 or AC Delco PT131.

A/C Hard Line With an A/C High-Pressure Switch Provision -- As far as I can determine, GM has discontinued the original part, and GM's A/C Line Adapter for Retrofit will not work. (Threads on the valve won't accept the A/C high-pressure switch above). The part, however, wasn't difficult to locate. In two yards I found a half dozen or so.

Two Relays – Painless Fan-Thom 30101. The wiring in the Painless Relay kits is marked for destination which makes running them pretty much foolproof.

Coolant/Thermal Switch - CarQuest TS217 (NO, Normally Open, comes on at 212). This part will fit in the pass side cylinder head.

Miscellaneous - wire (the various gauges are noted below), butt connectors, ring connectors, Posi-Locks, shrink wrap, convoluted plastic tubing, battery side mount, dielectric grease, etc. Good wire strippers and a crimper are helpful.

Mounts for the Relays: I used the stock relay-mounting piece (GM 10020508).

Other Issues:
Andy, in his set-up, uses a light to indicate when the fans switch on. I initially liked the idea but wanted something more stock in appearance. I purchased an Autometer bulb/socket (P/N 3220) and found that after very minor modification to the socket it would twist into the rear of the gauge cluster as if it were stock (find an empty socket and if need be, carefully cut away the plastic of the circuit board). Join one pigtail of the bulb/socket (16 gauge) to a wire going the coolant/thermal switch, and the second pigtail (16 gauge) to the ignition wire which enters the cabin. I copied the font of the "choke," "check engine," and so on in the gauge bezel (Arial narrow 16 in bold face), printed "Fans On", transferred the print to a transparency, and cut a square from the transparency to fit the inside of the bezel. The effect is absolutely stock. That said, in the end, I chose not to go with the light.


JamesC

 

Connections: The relays have four wires each.

From the relays, 1 wire each to the positive terminal of the battery (12 gauge) via the circuit breaker provided in the Painless kit. Both wires go to the battery side mount. See the next to the last pic.

 

From the relays, 1 wire each to the positive fan pigtails (12 gauge). Neg pigtails are grounded (12 gauge). See next pic.

 

I used existing grounds on either side of the radiator.

 

From the relays, 1 wire each to the ignition (18 gauge). I combined these two with a Posi-Lock 3-Way Connector (PLO812—a 14-gauge butt connector would do as well) and then used a 14-guage wire so that only one wire entered the cabin. I terminated with a spade and used an empty ignition slot in the fuse box.

 

From the relays, 1 wire each to the coolant/thermal switch. I combined the two wires in one end of a 14-gauge butt connector, then ran a 14-gauge wire to the coolant/thermal switch. (These first two wires would normally be the relay's ground (18-gauge).

 

From the A/C high-pressure switch pigtail, 1 wire to the coolant/thermal switch (18 gauge). I combined this wire with the 14-gauge wire from the relay as mentioned above, using a 12-10 gauge butt connector, then ran a 12-guage wire to the thermal switch. (You're actually combining three wires: two from the relay—already combined to one--and one from the A/C high-pressure switch). Note the hard line, high-pressure switch, and pigtail. The second wire from the A/C high-pressure switch pigtail is grounded (18 gauge). Note the coolant/thermal switch in the next pic.

 

The second leg of the coolant/thermal switch is grounded (12-gauge).

 

Grounds from high-pressure switch, coolant/thermal switch and battery. Note the circuit breakers and battery side mount.

 

My new 350 HO Deluxe. Note the relays on the driver's side bulkhead. Any advice or suggestions about how to make this set-up better are sincerely invited.

JamesC

 

What are your temps compared to the belt fan (in the process of doing the conversion myself, sans the AC)

Thanks

 

I don't know exactly. I took a 40-mile highway drive yesterday afternoon. The temp here in Kansas was 98 degrees. With air con blowing, I was only at the first peg of the temp gauge (yes, I know that they're not terribly reliable), which was certainly less than with the belt fan. I saw the real difference waiting in the drive-through at Mac's. In the past, I might have had to cut the air con all together and jump the idle speed up in order to cool the car down to a respectable limit. Not so yesterday. The gauge didn't even hit the 220 mark. So all in all, I'm satisified. Something else I like, though it has no real importance, is how quiet the electrics are compared to the belt fan and how clean they make the engine bay appear.

JamesC