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Tricking eFan to come on at lower temp.

LYKOS

LYKOS

NAXJA Forum User
Location
Bent Mountain Va
Somewhere, and yes I've searched and can't quite find the right search criteria, I've read about a trick to get your eFan to come on at a lower temp.

I remember something about a resistor inline to the Efan and that's about it. I'm no wiring guy go I need instructions.

Not talking about running a switch. I can do that and don't care to.


Any help?
 
Actually, I suspect that it's a resistor wired inline with the temp sensor, not inline with the e-fan. That would effectively change the resistance and fool everything downstream like the ECM and gauges. Inline with the e-fan would just change the resistance of the motor, and that's probably not a good thing.
 
Yep, it's something like that. I can't find the thread, or remember if it was on here or another forum. Was hoping it was a common mod someone could spit out real quick.
 
I wouldn't do that - it'll also mess with your fuel trims and the open loop to closed loop switch point since the ECU will think the engine is a different temperature from reality.
 
kastein said:
I wouldn't do that - it'll also mess with your fuel trims and the open loop to closed loop switch point since the ECU will think the engine is a different temperature from reality.
Click to expand...


Dangit!

That makes to much sense to ignore. Thanks for the input!
 
First off, what year is the XJ?
 
good point by old_man. The RENIX years have a thermoswitch for the radiator fan iirc.

I suspect this is on your 01, which means it's got one temp sensor in the thermostat housing for everything.
 
2001 I need to add that to my sig...
 
I know you said you didn't want to hear this, But i would just put it on a switch and go from there.This way if you forget to turn it on offroading it will still turn on.But when you start offroading you'll just learn to turn it on as soon as you hit the dirt.This is what i've done.

Good luck.
 
I'm not so much an off roader as I am a trailer hauler...

And having an old '01 I'm used to things getting hot and am trying to help with that.


But yeah, the switch apparently is going to be the best idea. I'll just wire the relay to trip off of a switched circuit so I don't drain the battery when I forget to turn it off.

Thanks all!
 
Make sure you get the switch/relay on the right side of the fan motor circuit. Ground side switched?
 
ChiXJeff said:
Make sure you get the switch/relay on the right side of the fan motor circuit. Ground side switched?
Click to expand...


Will do!


There are a lot of write ups on the switch mod I found when I searched. I feel pretty comfortable doing it.
 
There's a relay in the PDC. If you're comfortable wiring, put a second one in parallel with it (switch in parallel anyways) and run the coil with whatever you want. No CEL, no worries about running the battery down, no gangly wires and crap.
 
The fan motor is positive switched(via the relay in the PDC); the control side of the relay is ground switched.

I have a key-hot switch on a SPDT relay, connected directly to the fan, the stock power wire to the fan, and a fused lead to the battery. I don't see why you couldn't use a simple thermostat and relay control to operate the relay. This would provide power directly to the fan when needed, and leave it operating as stock when not needed. Something like this is available at most parts stores, and along with a SPDT relay, should be a simple modification.

http://www.etrailer.com/Radiator-Fans/Derale/D16720.html
 
Another Sweet Option

Well the only Have Cake And Eat It Too method I see for you is to wire a kit like one of these:

http://www.summitracing.com/search/...ne/Hayden-Electric-Fan-Controls/?autoview=SKU

Use a Single Pole Double Throw switch, and in one position it will run when the PCM wants to, on the other, it will use the temp range of the probe you chose. In either position you have automatic fan control, only the temp of on off range changes with the switch.
 
Why not replace the stock 195 thermostat to a lower temp one?
You can help your XJ two ways.....

1. Allow it to run a little cooler
2. Since you have a 2001 (0331) head running it cooler will help with the bad casting where it cracks from heat.

I always run a 170 degree fail safe thermostat in my 99-01's.
That allows the gauge to read 190 inside instead of 210
 
As I see it, turning the fan on at a lower range is a band aid fix. What are you doing with the XJ and / or what is wrong with it that temps are climbing? What's the problem that you are trying to solve?
 
If you are referring to the OP, he says why he wants to do this in Post #10. Assuming that the Jeep is otherwise performing properly cooling wise, I don't see this as a band-aid fix, at least for earlier models -- can't speak for '01s.

Just my interpretation FWIW.

I never cease to be amazed by the 170* thermostat crowd. I can only speak for my '93, but after I had driven it for about three years, I found that the PO had installed a 165* stat. I thought, wow, I'll put in a 195* and everything will be so much better. Did it and not one thing changed -- MPG, performance or cooling. If I understand correctly, the 4.0 was designed for the 195* so I will stick with that. This is my anecdotal one XJ experience, again in the FWIW department.

Technically speaking, I just don't understand how a lower temp thermostat can cause a 4.0 to run cooler at operating temps???
 
yossarian19 said:
As I see it, turning the fan on at a lower range is a band aid fix. What are you doing with the XJ and / or what is wrong with it that temps are climbing? What's the problem that you are trying to solve?
Click to expand...

It's not a band aid fix if it's preparation for heavier duty use.

Given the nature of the intent of use for my XJ I've made some pretty substantial mods to my cooling system.

I've done the research and have installed a HD radiator and tri-fan cooling set up with both manual and automatic controls.

But before I did any of that I made sure the engine was in proper tune and all components were working properly. In that case it was cooling fine under normal use. Waiting for it to overheat coming up a 7% grade with a trailer is too late. hence the modifications.:skull2:

Before I start really loading my trailers I will also re-gear to help the engine work less and the tranny last longer.


Thanks for all the input.
 
Pelican said:
I never cease to be amazed by the 170* thermostat crowd. I can only speak for my '93, but after I had driven it for about three years, I found that the PO had installed a 165* stat. I thought, wow, I'll put in a 195* and everything will be so much better. Did it and not one thing changed -- MPG, performance or cooling. If I understand correctly, the 4.0 was designed for the 195* so I will stick with that. This is my anecdotal one XJ experience, again in the FWIW department.

Technically speaking, I just don't understand how a lower temp thermostat can cause a 4.0 to run cooler at operating temps???
Click to expand...

I don't get that either. The lower temp would basically stay open constantly and the coolant would not spend enough time in the radiator (in the summer) to be cooled and hence would create overheating issues at low speed and heavy duty use.

Int he winter it wouldn't stay in the block long enough to warm up to operating temps. So the engine would perform poorly.

I run a Stant 190' in mine and it seems to do quite well. I actually ordered it by mistake, wanted a 195. But still, it seems fine an m temps run about 197 to 205 in city driving.
 
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