Wiring Aftermarket Single Speed Fans

[RebekahsZ]

I've been all over this forum's search and all over LS1tech's search, so please nobody chew me out. I have a wait4meperformance modified engine harness. I have dual single speed fans that came with my aftermarket Champion aluminum radiator and shroud. From LS1tech, I have picked up that the simple and effective way to wire the fans up is from the low-speed wire using a single relay. Then I guess I just cut off the high speed wire and put some heat-shrink over the end? I don't know enough electrical engineering to know what size relay to use, and I don't know how to wire the fans down-stream of the relay. I assume it will be some sort of an in-series arrangement, but I don't really have a clue. Help me if you can, drawings or photos will really help. I'm ready to get some relays coming in the mail so I can tear into the wiring next weekend. It seems like wiring is where there is the most divergence on how this swap is done-I want to keep it as simple as possible.

[Dudeboy]

Like you, the wiring part worried me but, I jumped right in and re-wired the my whole car. I bought books on wiring a hot-rod and research all over the net. For me learning how relays work was the big picture, and then how do they work with a LS PCM and electric fans. Check this out on relays http://www.alanhorvath.com/54chevy/understanding_relays.php, and also go to the Painless wiring web page, and in the product manuals they have diagrams for the relays they sell. Also, go to hotrodlane.cc, and they also have some fan diagrams on there LS1 Tech install page. Do you have a wiring diagram from the wait4meperformance modified harness ? also will you have air conditioning ? I do not have air conditioning so my Taurus fan is wired for low speed and my car IF I EVER GET IT ON THE RODE ! will be a weekend car show cruiser, maybe a few runs at the drag strip. I hope this helps.

[ktm]

Wiring up a single relay is VERY easy. The bottom of the relay will have 4 or 5 pins numbered: 85, 86, 87, 87A and 30. 87A is the center pin and is not used in this application. A 4 pin relay will not have an 87A pin.

 

Pin 85 is ground. In this case, Pin 85 should connect to the LOW SPEED wire from the GM PCM. The PCM will pull to ground, thus energizing the relay.

Pin 86 is ignition hot. The relay will not close until Pin 85 is pulled to ground by the PCM. Usually Pin 85 is wired to ground and the relay is energized by Pin 86 when fed ignition hot power.

Pin 87 is the power TO the fan.

Pin 30 is fused power FROM the battery.

 

 

You do not have to do anything with the hi-speed wire on the PCM. It is not activated until 235 degrees (IIRC) or if the A/C is turned on.

Edited November 21, 2011 by ktm

[RebekahsZ]

Great. I have a relay coming in from Summit and I'll apply your advice when it arrives. I've been looking at a wire-sizing chart based on amperage load of the motor being powered. My fans were ebay and include no specs. Any rule of thumb on the size of the power wire, and what amp fuse i should use when powering both fans.

 

I started draping my engine harness out today after finishing up the radiator mock-up.

 

Thanks!

[ktm]

Find out what amperage the fans pull when turning on. This will always be higher than the operating amperage. Size your fuse for the amperage draw when they turn on otherwise you'll be popping fuses like mad. My Flex-a-lite 210s pull 20 amps when operating and near 30 amps when turning on, so I use a 30 amp fuse.

 

 

I found this chart a long time ago when I was wiring up my car. I thought it was a PDF/image, but it was a Excel file. Quite honestly, you can't go wrong with 10 ga wire. Your Ebay fans probably draw no more than 20 amps when operating or 30 amps on startup and the length of wire will be less than 10 ft. Your relay will most likely not be sized for 10 ga, but you can make it fit though it will be tight.

Edited November 22, 2011 by ktm