How to hotwire fan?

iwannanSC

Registered User
Hey,

BOTH my low-speed and high-speed fans don't work. I replaced the IRCM and that clearly wasn't the problem. I want to hot-wire it so that it just comes on whenever the car is running. If anyone knows how to do this, you input would be much appreciated. Thanks,

Matt
 
The #14 wire on the ICRM controls the low speed fan. If it is cut so it is left open, the low speed winding on the fan motor will be energized all the time. You could hook a thermostatic switch into that with a relay to break the connection at a different temp.

The catch though is that there is a high speed winding in the fan motor that should not be energized when the low speed winding is. If they are both powered, the fan motor will see excessive wear.

The #17 wire controls the high speed winding and is simply grounded to activate the high speed fan.
 
Do not cut wire 14. It bogged down my starter when ever I tried to start the car. It would remain on while the starter was cranking. Buy the Flex-a-lite adjustable therm switch and a Licncoln town car fan relay(30 bucks for both). Now I can infanantly adjust when the fan goes off and comes on.
 
I'm confused. So if I cut wire #14, the low-speed fan will run whenever the car is on, right? If so, then does then high-speed fan ever kick on, and if so, when?
 
Wiring it like this diagram that David Dalke (XR7Dave) drew, will shut off the low speed when high speed comes on. It will also maintain all standard EEC settings and functions, such as turning on the low speed fan when the AC or Defrosters are turned on.

fan%20relays.jpg


David
 
If you unplug your Coolant Temperture Sensor the fan automatically comes on no matter what for the computer doesn't know if your running hot or cold.

Just a suggestion if you don't want to cut anything.

-Tim
 
David has the best answer. Which is to wire in some relays and switches to override the ECM method of controlling the fan, yet allow the ECM to override the relays for certain circumstances.

If you cut the #14 wire, the fan will start running as soon as battery power is available. As factoryblue pointed out, this puts additional stress on the electrical system during starting. A questionable starter or battery with the fan running can cause a slow crank.

Thrty5thSC is one of a few people that have cut the #14 wire, and never had a problem with the high speed fan coming on or if it did, it wasn't on sufficiently long to cause a problem. The concern with the high speed and low speed fan on at the same time is really only for people in areas or circumstances where it is really, really not outside.

So, if you want to do it right. Follow the diagram David provided. If you want to do it but don't have the skills or want to mess with it a lot, people have had success just cutting the wire, splicing in a switch, and then leave it on most of the time, and off when necessary. (Just don't forget to turn it back on)
 
I've been following the other thread about the same subject and currently have a switch & 200deg sensor (on the rad) spliced in and grounding the #17 wire for the high speed. Without putting in the full wiring relays & t/switches on the above diagram would I be better off just putting the switch and sensor in line with wire #14 (low speed). My understanding is that you can't ground #14 directly like you can the high speed.
Thanks, Jim.
 
I've been following the other thread about the same subject and currently have a switch & 200deg sensor (on the rad) spliced in and grounding the #17 wire for the high speed. Without putting in the full wiring relays & t/switches on the above diagram would I be better off just putting the switch and sensor in line with wire #14 (low speed). My understanding is that you can't ground #14 directly like you can the high speed.
Thanks, Jim.
 
I have a question, in the diagram that david put up, are the high speed and low speed adjustable thermostat switches toggle switches? I have bought everything else for the setup and the last thing is the switches.
 
where do i get those. I went to my local auto parts store, they usually have everything, even motorcraft parts that are a quarter of the price cheaper than the dealer, but they only had the single switch with the probe and a whole bunch of wires, not what I need.
 
All done. The setup works great. The fans work great, but the low speed fan comes on as soon as the car is started, but the high speed fan works with the switch. It doesnt bother me cause the car doesnt ever get hot. Thanks for the diagam and the info.
 
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