Electric fan operation...??

I have converted my closed cooling system to the open system, but have a question or two about the sensor for the electric fan.

I used the t-stat housing that incorporates the fan sensor, but I have no idea at whattemperature the fan should come on at, so can anyone tell me?

I have not seen the fan come on at all (except when the AC is on) since I did the conversion. Is it possible to hook the wires up backwasrds? There are only two wires and they are both the same color with no distinguishing markings.

IIRC these number is not adj. It is what it is. if its coming on with AC, you likely did it just fine. The AC going on, automatically turns on that fan. To the best of my knoledge, It dosent go thru the temp switch. The temp switch is a secondary circut. the temp sender controls the fan in the event of higher engine temps.

On mine the temp switch is just that, a switch, no polarity. It just allows current flow when its switched by the preset temp point.

CW

Yes, that is my understanding so far, but do you have any idea what the set temperature is for the fan to come on?

I probably have not reached that temp due to the fact that I installed a 3 row radiator and it runs at about 190. It did get up to about 220 for a short time while just sitting in my carport, but the fan did not come on.

Yes, that is my understanding so far, but do you have any idea what the set temperature is for the fan to come on?

 

I probably have not reached that temp due to the fact that I installed a 3 row radiator and it runs at about 190. It did get up to about 220 for a short time while just sitting in my carport, but the fan did not come on.

220 is still normal operating temp.

if it gets to 230 and doesn't come on...there's a problem

OK...that is what I was hoping. I doubt it will get that high any more with this radiator.

Thanks... :cheers:

Any and all other input is still welcome if you have something else to offer on the specs for this.

According to my FSM, the electric fan comes on at 190*. The temp sensor supplies a signal to the ECU; then ECU then sends a ground to the aux fan reply to turn the fan on. Turning on the A/C also provides a ground path to the same relay to turn on the fan. That said, my aux fan has NEVER come on at 190*. The few times it has come on was in the middle of summer after a pit stop of about ten minutes or so. The temp gauge reads about 220* at this time. The fan runs for about five minutes or so, then shuts down at about 190*. So I wouldn't worry about it not coming on until 210-220 degrees or so.

Thanks... I probably would have found that when I got back to work tomorrow, but I wanted to know ASAP so I could look in to it if there was a problem as my wife is using this as her DD right now until I get some other work done on here YJ next weekend.

The polarity of the wires does not matter as this acts just like a like switch, you are supplying power to the switch, when it gets hot it simply closes the switch sending power (12v) back to the circuit and viola the fan comes on.

Just for reference, the yellow wire from the wiring harness is the hot wire and the black wire is the ground.

 

Just for reference, the yellow wire from the wiring harness is the hot wire and the black wire is the ground.

Thanks for that info.. I will definitely use it if there seems to be a problem.

According to my FSM, the electric fan comes on at 190*. The temp sensor supplies a signal to the ECU; then ECU then sends a ground to the aux fan reply to turn the fan on. Turning on the A/C also provides a ground path to the same relay to turn on the fan. That said, my aux fan has NEVER come on at 190*. The few times it has come on was in the middle of summer after a pit stop of about ten minutes or so. The temp gauge reads about 220* at this time. The fan runs for about five minutes or so, then shuts down at about 190*. So I wouldn't worry about it not coming on until 210-220 degrees or so.

The original poster doesn't have a '91. In the Renix models, the ECU is not involved in controlling the aux fan. The temp sensor in the radiator is an off-on switch that controls a relay, which in turn controls the fan.

Since the original temp sensor from the radiator tank won't fit the smaller hole in the t-stat housing, you had to have used a different sensor. If you used the one for a '91 and newer XJ/MJ, it's NOT a switch, and it will not turn your fan on.

This is just one of the reasons why I don't advocate doing the open system "upgrade." NAXJA members spent years looking for a sensor that would do the job. One guy said he found it in an older Honda. Three other people showed why he was wrong. Then someone said a Corvette temp sensor was the answer. IIRC that, too, proved to be a false lead.

I'd suggest getting the one for an '88 MJ that has idiot lights. That's an on-off switch. If the temp gets hot enough that it would trigger the warning light -- that's when you want the fan to come on. Of course, I'd rather have it come on a tad sooner, but that's better than nothing. You can also wire a toggle switch in parallel with the sensor so if you see the temp rising you can switch on the fan manually.

OK...that makes sense. I did use the "sensor" for the newer engines, so it will not activate the fan.

Time for a little research.

If you used the one for a '91 and newer XJ/MJ, it's NOT a switch, and it will not turn your fan on.

Actually it is a switch and will work without issues; several (including myself) have done it without issues. The key is to use the wires as I stated above. They can be found in a ribbed protector running down the left hand inner fender. Out of this ribbed wiring sleeve will be a connector with a yellow and black wire.

Also TurboCity sells a GM thermo switch that will fit the housing as well. It only has 1 wire coming out of it, so you'll have to use a relay for it to do it's job correctly. This option is popular if you want to put your fan on a switch as well, as you can simply run 2 lead wires to the "switched" side of the relay.

OK...I guess I am going to do a test that came to mind just now. I am going to take it [sensor/switch] out of the housing, hold it with a long set of channel locks and heat it with my little hand held propane torch to see if the fan comes on. Anyone know a reason that this will not tell the story?? I know it will not tell me the temp that it activates at, but it should answer the question about it's ability to do the job.

Since the original temp sensor from the radiator tank won't fit the smaller hole in the t-stat housing, you had to have used a different sensor. If you used the one for a '91 and newer XJ/MJ, it's NOT a switch, and it will not turn your fan on.

 

Then someone said a Corvette temp sensor was the answer. IIRC that, too, proved to be a false lead.

 

I'd suggest getting the one for an '88 MJ that has idiot lights. That's an on-off switch. If the temp gets hot enough that it would trigger the warning light -- that's when you want the fan to come on. Of course, I'd rather have it come on a tad sooner, but that's better than nothing. You can also wire a toggle switch in parallel with the sensor so if you see the temp rising you can switch on the fan manually.

Didn't see he had a non-HO - sorry. But actually the Corvette temp sensor switch does work to trigger an electric fan relay. Borg Warner part #TFS19 or Niehoff part #DR137XL, on at 215 and off around 195. I'm gathering parts to get rid of the mechanical fan and replace it with an electrical Zirgo 2500CFM fan. I got one of these Corvette temp sensors (Borg Warner TFS19) and installed it on my thermostat head this weekend, tee-ed in with the existing aux fan switch. I want separate controls for each electric fan. I wired the Corvette temp sensor to apply a ground to the coil of a relay that turned on the Zirgo fan through the power contacts. It worked fine; the fan came on right at 200*, and shut off at 190*. :cheers:

I think the '88 MJ idiot light sensor would have a too high temp turnon, prolly about 220* or so.

Very good. It appears the the local Advance Auto carries the BW TFS19 so I will be making a stop there tomorrow. The picture looks like it should even have the correct threads to fit the hole.

Yes it does, 3/8" NPT. What sensor do you have on your stat housing now? What are the temp ON/OFF markings on it? You probably know this, but this switch (I prefer sensor, but it is a switch :D ) can only be used to apply a ground to the coils of a relay, not to activate the fan itself.

Just put in a switched relay that is also switched by your ignition.

When you want your electric fan on, turn on the switch, when you want it off, turn it off.

It is not really necessary to have a T-Stat controlled fan in My Opinion.

Than again I think that power windows are awful. I have a 29 year old set of window winders in my MJ... My right arm and my left arm.

Just put in a switched relay that is also switched by your ignition.

 

When you want your electric fan on, turn on the switch, when you want it off, turn it off.

 

It is not really necessary to have a T-Stat controlled fan in My Opinion.

 

Than again I think that power windows are awful. I have a 29 year old set of window winders in my MJ... My right arm and my left arm.

Then you depend on human intervention. In your case, maybe that's okay. In mine, sometimes okay, sometimes not. :cry: I'd rather be looking out the window than looking at gauges all the time. I like my power windows too. :cheers:

I was not aware that the switch had temp markings on it, but yes, I am now aware that the one in that pic is not going to do the job. I am going to pick up the TFS19 today.

If I had no other choice, I would wire in a manual switch, but I much prefer to have things work as intended. I guess in my research prior to doing this I did not take in to account the fact that the newer style system has the ECU & relay set-up, but thanks to the great group here...it seems that my ignorance has been overcome ;) :cheers: .

Thanks again for all the help. I'll post results ASAP, but the wife will be sriving it today, so it will be late tonight before I can touch it to swap the switch.

Well, you can always wire in a manual overide switch. Be good to have if you're wheeling. But the original aux fan has been doing it's thing at the right time for 17 years now, so I doubt I will. Here's a generic schematic for 2-fan wiring with a controller that shows an overide switch.

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Well...I could not come up with a switch today as nobody carried, nor could the get the Borg Warner part, but I did manage to cross reference it to a Standard part# TS195 and got that ordered for tomorrow.

Tina drove it today and said it stayed under 200 at all times without the fan working 8) ...of course it was pretty cool here today with highs only in the mid 60's.

I got the TS195 switch and installed it last night. Now all I have to do is get the engine hot enought to make sure it works as it is supposed to.

I got the TS195 switch and installed it last night. Now all I have to do is get the engine hot enought to make sure it works as it is supposed to.

How's the fan working? Got any start / stop temps using the TS195?

Sorry for the delay, but our sons car broke down so we had to loan out our MJ for a while. They have had it since the day after i put that switch in so I have not been able to check it.

I'll try this weekend as we just got it back and he now has a 1996 XJ that is showroom clean with only 59K on the ticker :cheers: :D .

Sorry for the delay, but our sons car broke down so we had to loan out our MJ for a while. They have had it since the day after i put that switch in so I have not been able to check it.

 

I'll try this weekend as we just got it back and he now has a 1996 XJ that is showroom clean with only 59K on the ticker :cheers: :D .

Nice ride. :D Brent, you must trust your son very much to lent him your MJ. No way would either of my daughters touch mine. :cheers: Don