OEM aux fan sending unit alternatives.

Roxtar · Jun 7, 2004

Does anyone know of a sending unit to take the place of the aux fan sender that threads in the t-stat housing? I want one that turns on the fan at a lower temperature but, obviously, has to work with the computer. My Jeep dealer doesn't show different temp range senders avail.

martin · Jun 7, 2004

I take it you have a 99XJ or that what listed on your profile. You want the fan to come on earlier you say. It your engine running hotter than it use to?

I believe the temp sensor in your thermostat housing "IS" the temp sensor for the engine. It provides the signal for your dash board and the sofltware in the computer uses the "data" to figure out when to turn on the electric fan.

If i hae gathered from reading posts on her the temp sensor you want to replace is a "sensor" not a "switch" like my 88 XJ has in the radiator.

I recommend you replace the fan clutch for the mechanical fan if you notice the engine is running warmer. The clutch has a life of 5 years, some longer and some shorter, but 5 years is a good number. Your XJ is 5 years old so replace the fan clutch before you start changing out sensors. Also there no 100% accurate test for those fan clutches, so don't even try... just replace, that should fix your problem.

Also if your vehicle has gotten hot - over 225F - then replace the thermostat and radiator cap. High temps can damage them and they may not hold pressure or open too last and close too soon. I recommend you get the thermostat at the dealer.

Roxtar · Jun 8, 2004

martin said:
I take it you have a 99XJ or that what listed on your profile. You want the fan to come on earlier you say. It your engine running hotter than it use to?

I believe the temp sensor in your thermostat housing "IS" the temp sensor for the engine. It provides the signal for your dash board and the sofltware in the computer uses the "data" to figure out when to turn on the electric fan.

If i hae gathered from reading posts on her the temp sensor you want to replace is a "sensor" not a "switch" like my 88 XJ has in the radiator.

I recommend you replace the fan clutch for the mechanical fan if you notice the engine is running warmer. The clutch has a life of 5 years, some longer and some shorter, but 5 years is a good number. Your XJ is 5 years old so replace the fan clutch before you start changing out sensors. Also there no 100% accurate test for those fan clutches, so don't even try... just replace, that should fix your problem.

Also if your vehicle has gotten hot - over 225F - then replace the thermostat and radiator cap. High temps can damage them and they may not hold pressure or open too last and close too soon. I recommend you get the thermostat at the dealer.

I've replaced both fans with (2) 12" electric fans. I'm now running them off that sensor. It works fine but the sensor, since it's made to kick in the aux fan, not the main one, doesn't turn them on till about 220 degrees. I was looking for ways to do exactly what I'm doing now, just at a lower temperature.

ZombiE · Jun 8, 2004

You have 4 options.

1. Return back to the original fan setup, you will in future anyway, might as well save yourself 3000 headaches and do it now.

2. Install a manual switch so you can flip it on at anytime.

3. There is also an Aux fan kit at Autozone that you could try.

4. Search. There are a lot of individuals that have done this before and most if not all have returned to the original setup.

Alex

Roxtar · Jun 8, 2004

ZombiE said:
4. Search. There are a lot of individuals that have done this before and most if not all have returned to the original setup.

Alex

Yea, but they're not as good as me.

Dr. Dyno · Jun 8, 2004

kid4lyf said:
I've replaced both fans with (2) 12" electric fans. I'm now running them off that sensor. It works fine but the sensor, since it's made to kick in the aux fan, not the main one, doesn't turn them on till about 220 degrees. I was looking for ways to do exactly what I'm doing now, just at a lower temperature.

I tricked the engine's computer into switching on my dual electric fans at 210* instead of 220 by splicing in a 4Kohm resistor across the two wires coming from the coolant temp. sensor in the t'stat housing. The fans switch off again at 185*F, just above the opening temp. of my 180* t'stat. Here's my write up:

http://www.angelfire.com/my/fan/CTS.html

Roxtar · Jun 8, 2004

Dr. Dyno said:
I tricked the engine's computer into switching on my dual electric fans at 210* instead of 220 by splicing in a 4Kohm resistor across the two wires coming from the coolant temp. sensor in the t'stat housing. The fans switch off again at 185*F, just above the opening temp. of my 180* t'stat. Here's my write up:

http://www.angelfire.com/my/fan/CTS.html

That's exactly what I was looking for. Does this mod effect anything else in the computer?

Eagle · Jun 8, 2004

kid4lyf said:
That's exactly what I was looking for. Does this mod effect anything else in the computer?

Yes, it does. What Dr. Dyno neglected to mention is that he is in Saudi Arabia and his XJ is not U.S. spec. The same sensor also provides data to the injection and ignition. The sensor feeds the ECM, and the ECM then controls the aux fan, the injection, and the ignition. So if you wire in a resistor as Dr. Dyno suggested, on your U.S. spec XJ you not only fool the fan(s), you also torpedo your engine controls.

Eagle · Jun 9, 2004

BTW -

I see that you have a version of this question running on the Mod Tech Forum as well as this one. Our forum guidelines prohibit cross-posting. In the future, please choose the most appropriate forum and post your question once. Since dual electric fans are a modification, I am closing this thread.

OEM aux fan sending unit alternatives.

Roxtar

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martin

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Roxtar

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ZombiE

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Roxtar

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Dr. Dyno

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Roxtar

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Eagle

Lifetime NAXJA Member

Eagle

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