Fan Switch

[88mjgilley]

I just changed my comanche over to the open cooling system has anyone ever tried to wire up a ho thermostat mounted fan switch into the wireing harness by splicing into the pre ho raidtor mounted fan switch wires?

[ncmountainMJ]

nevermind..... had to reread the question

Edited October 27, 2012 by ncmountainMJ

[HOrnbrod]

I just changed my comanche over to the open cooling system has anyone ever tried to wire up a ho thermostat mounted fan switch into the wireing harness by splicing into the pre ho raidtor mounted fan switch wires?

 

Are you asking because you installed a new HO radiator (with the fill cap) to convert to an open system and this radiator did not have a threaded bung hole for the original Renix temp sensor? Most aftermarket replacement HO radiators have the bung in the left side tank so you can retain the fan sensor.

 

There have been a lot of writeups for using a replacement temp sensor in the HO themostat housing to control the aux fan (the Corvette sensor come to mind) but none have worked well that I recall.

[88mjgilley]

ya that was what i was wondering i put in the raditor out of my 96 xj i also have a few ho thermostat houseing so i was going to attempt to wire the thermostat mounted fan switch into the old fan switch wireing since the ho raditor doesnt have the locationj to install that factory switch so it would still come on when needed and i will also be wireing it into a switch but i always wire them up so they will come on when needed since i forget to turn it on from time to time

[ParadiseMJ]

Most aftermarket replacement HO radiators have the bung in the left side tank so you can retain the fan sensor.

 

There have been a lot of writeups for using a replacement temp sensor in the HO themostat housing to control the aux fan (the Corvette sensor come to mind) but none have worked well that I recall.

 

Like he said ^^^^

 

There are 3 "sensors" for engine coolant temps on a Renix Jeep.

 

There is the gauge (or light) sensor...it just provides a reading on the gauge or light...the one on the head. It's a sender.

There is the Coolant Temperature Sensor (CTS) on the driverside lower block. This provides the ECU with info for air/fuel mixture. It's a sensor

There is the radiator temp switch. It's sole function is to send a signal to the auxillary electric fan relay. It's a switch.

 

The Corvette also uses a switch, and it can be mounted in the HO t-stat housing bung, as in, it fits and it WILL do the same job. I have no idea which years or what P/N. Also, the HO wiring can be spliced but it would not turn the fan on because it's a different type of signal. I mounted an HO sensor on an HO t-stat housing, and it plugged right in to the existing e-fan connector and existing wiring, I thought I had it licked.

 

So, it didn't work and I couldn't figure it out (I am electrically retarded). I just finally wired in a switch in the cab, which I actually like better.

 

http://www.olypen.co...aigh/auxfan.htm

 

BUT like hornbrod sez, take a close look at the new radiator. Some have the bung already but it's hidden behind a knockout (like on an electrical junction box). If the knockout is there you may just get lucky, because it's already threaded.

Good luck.

[Eagle]

ya that was what i was wondering i put in the raditor out of my 96 xj i also have a few ho thermostat houseing so i was going to attempt to wire the thermostat mounted fan switch into the old fan switch wireing since the ho raditor doesnt have the locationj to install that factory switch so it would still come on when needed and i will also be wireing it into a switch but i always wire them up so they will come on when needed since i forget to turn it on from time to time

 

The problem is that the sensor in the HOs is not a "switch." It doesn't have an OFF and an ON condition. It's a variable resistance sensor. You could use the temp sender for an early (Renix) XJ or MJ with idiot lights, but that won't turn on the fan until the temperature is already too high.

 

IMHO your easiest "fix" (at least for now) is to wire a toggle switch to control the aux fan relay. Watch your gauge, and flip the switch if the gauge reads higher that 210 degrees (straight up).

[HOrnbrod]

The difference between the HOs and the Renix is the fan relay coil feed. The Renix fan relay is energized by a 12V switched signal from the fan switch mounted in the radiator, while the HO aux fan relay is turned on by applying a ground to pin 31 of the ECU from the thermostat housing fan switch. The easiest way to trigger the aux fan in a Renix that has been converted from a closed to open system is to use an aftermarket radiator that has both the fill cap and the fan switch bung hole. The factory HO radiators had no provisions for the fan switch bung.

 

Another way to do it would be to install a temp switch in the HO thermostat housing and wire it to switch 12V instead of a ground as in the HO models. This switched 12V signal would be tied directly to the wiring formerly connected to the Renix fan switch in the radiator. As Eagle says, the problem with this setup is to find a temp switch for the HO thermostat housing that will switch at the correct temperature. I have not seen any writeup where anyone found the proper switch. The much yakked about Corvette temp switch turned on too late.

[RDAN1]

 

But like hornbrod sez, take a close look at the new radiator. Some have the bung already but it's hidden behind a knockout (like on an electrical junction box). If the knockout is there you may just get lucky, because it's already threaded.

Good luck.

 

Does anyone know which brand/brands of aftermarket radiators have both the fill neck and the knockout for the temp switch? My 88 4.0 needs a new radiator and the ones I've seen so far don't have both, either one or the other. ???????.

[HOrnbrod]

Does anyone know which brand/brands of aftermarket radiators have both the fill neck and the knockout for the temp switch? My 88 4.0 needs a new radiator and the ones I've seen so far don't have both, either one or the other. ???????.

 

Just a quick look on Ebay turmed up these three with the bung and fill:

 

Champion 3-row 1193-2

FFD CHER-3

Silla 1-row 2268AA

 

I use an FFD 2-row and the bung is circled in RED.

 

[RDAN1]

Just a quick look on Ebay turmed up these three with the bung and fill:

 

Champion 3-row 1193-2

FFD CHER-3

Silla 1-row 2268AA

 

I use an FFD 2-row and the bung is circled in RED.

 

 

Thanks Don. I just sent FFD a message and asked if they still have one like you bought as it would be my preferred one. I had previously inquired of one of the silla vendors about the AA single row but never got an answer.

 

EDIT: Just received an automated response: they have evacuated their building due to Hurricane Sandy..They will reply when they return..Good Luck to them and everyone in the way of the storm.

[RDAN1]

Thanks Don. I just sent FFD a message and asked if they still have one like you bought as it would be my preferred one. I had previously inquired of one of the silla vendors about the AA single row but never got an answer.

 

EDIT: Just received an automated response: they have evacuated their building due to Hurricane Sandy..They will reply when they return..Good Luck to them and everyone in the way of the storm.

 

Today I received a response from the guys at FFD. They indicate they haven't changed their radiator design in over 5 years and if purchased since then, it would be like the one in the picture Don posted. They didn't confirm that it had a "bung" ...only that they hadn't changed it....????? Don: How long ago did you purchase yours from FFD?

[HOrnbrod]

Today I received a response from the guys at FFD. They indicate they haven't changed their radiator design in over 5 years and if purchased since then, it would be like the one in the picture Don posted. They didn't confirm that it had a "bung" ...only that they hadn't changed it....????? Don: How long ago did you purchase yours from FFD?

 

I purchased it about 1-1/2 years ago. Mine sure had the bung because after I installed it and started to fill it, coolant was leaking out of the bung plug. It wasn't tight and I didn't check it - my bad. I pulled the plug, wiped some Permatex thread sealant around it, and reinstalled. No problems. :thumbsup:

[RDAN1]

I purchased it about 1-1/2 years ago. Mine sure had the bung because after I installed it and started to fill it, coolant was leaking out of the bung plug. It wasn't tight and I didn't check it - my bad. I pulled the plug, wiped some Permatex thread sealant around it, and reinstalled. No problems. :thumbsup:

UPDATE: Today I received an FFD Radiator and indeed it has the bung (with the correct Threads!) to install a Fan Temp switch. Pictures below of the Radiator with the bung plug out and another of 2 Fan Temp switches..an OEM One and an aftermarket one (TS258 from Rock Auto.)

With this radiator the aftermarket fan switch fits perfectly however the OEM one is too deep and won't snug up tight due to the radiator internals. I'm installing it tomorrow..Thanks Don for the lead on this and the solution to a problem finding a radiator with a bung to accommodate the fan switch and with a fill neck!!!!.

[HOrnbrod]

Glad it worked out for you. :thumbsup: And just noticed you have an AX-15 so will have no need for the auto tranny coolant lines. There's a slight issue with the lower elbow fitting hitting the frame.