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A/C AUX fan switch (sort of)

R

ROKTAXI

NAXJA Forum User
Location
Grand Juntion, CO
I'm wanting to have my AUX fan to come on as it does when the A/C is on, BUT WITHOUT having the A/C on.

I want to retain the default (factory) A/C auxiliary fan on/off settings when I run the A/C.

I have a manual switch now, but would rather have it come on automatically at the default A/C settings. Is this possible to intercept a wire to accomplish this?
 
Thanks for your reply. Basically I want it to come on / go off at the same settings that happen when the A/C is on. I believe it's 195 on / 190 off ??
 
Somebody correct me if I'm wrong, but I believe your '94 is the same as my '93 in that the aux fan is always on when the a/c is on and does not respond to changes in coolant temps.

To vary the on/off temps, you can easily install a separate controller. I have a Hayden unit (~$45) with an external radiator probe that has worked perfectly for about five years.
 
On my '94, when the A/C is on and temp drops to 190, the aux fan goes off.

I was hoping not add a separate controller if possible.
 
I think I see what you are trying to accomplish. I forget what the stock on-temp is for the aux fan -- 200/205? -- but whatever it is, you want the fan to come on at 195 using the control source for the a/c. I'm assuming the signal comes from the PCM but some HVAC guy is going to have to chime in on this one.

Good luck.
 
Except for the Renix XJ's the fan is controlled by the PCM. For most of us, it come on when the temperature is 220+ and of about 210. From,... I think 1989 to 2000, it is possible to add an independant relay and manual switch to control the fan. I have heared the 2001 XJ will throw a CEL code if you do that.

You may be able to wire in another temperature switch of your likeing to turn the fan on at a lower temperature. Many on this forum have done that and posted the procedures which are easy to follow. Do a search, you will find something.
 
I have a switch for mine(used a stock rear wiper switch and removed the blank plate to the right of the steering wheel). I can switch it on anytime. With the switch off, the fan comes on when the a/c is engaged and when temps hit 218*, as normal. When I hit the switch, the diode in the extra relay shields the pcm from knowing it's turning on w/o its instructions and thus doesn't set a P1491 CEL(Aux Emissions Control). Thank fyrfytr for the write-up:
http://www.naxja.org/forum/showthread.php?t=1025399
 
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I'm not to sure I understand your question but I have my aux fan wired to a switch, all i did was wire up a relay with the power out going straight to the efans positive wire. It functions exactly like stock but i can override it and run the fan with a switch whenever I want to.

Key to having no CEL is you have to power the fan FORWARD of the computer, meaning don't activate it at the ECM. Run a relay straight to the positive wire and splice into it right near the efan itself.

Sorry if I'm misunderstanding your question here bud.
 
Actually I think i get what your saying now, you want your efan to come on at the temps it would come on with the AC running? The thing is the efan comes on when the aircon system reaches a certain psi not a certain temp. Without the ac on the efan will only come on when the cooling system reaches 218 or something around that.

So your saying yours doesn't come on by itself around 218?? If so then your coolant temp switch could be shot or the fan relay could be bad? Just thoughts here
 
This is what I thought. The OP's cycling on/off at ~195/190 must just be coincidence.

If no 195 signal exists from the PCM, I assume he will have to add a sensor of some sort that will control the fan relay if he wants the fan to engage at 195. I believe this is the turn-on temp I have my Hayden control set at but would have to check (non pertinent in any event).
 
techno1154 said:
...the fan is controlled by the PCM.....
Click to expand...
You're right but I was trying to see if there's a way to intercept that, but the more I think about it, I don't think it's possible.

Like was mentioned by you and pelican, I guess my only option is to add a thermostat switch like the one I have for my Taurus fan. I just may wire them together so I don't have to have 2 different t-stats. I would prefer to have them separate.
 
When I added a switched ground to the stock aux fan relay w/o the additional relay, my 96 obd2 would get the P1491(pcm didn't like an external source telling it when to ground the relay; the additional relay shields the pcm from knowing). Maybe you obd1s and the renices can get away without the additional relay without having a CEL, but obd2s(96+s) cannot. Fyrfytr's writeup is the way to wire it. You can have a $20 adjustable temp controller feed the signal to the additional relay if you don't want to switch it manually.
 
Bringing one back from the dead! Gradon, do you have a write-up specific to the 96 year model(E-fan over-ride switch)?

You PM box is full!
 
The 96 has the same dark blue with pink wire under the PDC that activates the aux fan relay. I used one of the blank relay locations(mine is a SE stripper model, so only had the 4.0 and A/C) to put the shielding relay. I'll go out and take some pics. Anyhow, I guess my failure to renew membership reared its head with the limited pms.
 
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