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Unread 05-11-2013, 11:21 AM   #1
Karlinwa
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1989 FSJ Cherokee 
 
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Replaced Rad Temp Switch No elec fan

1989 Jeep Cherokee, 4.0, Auto, 4x4, A/C.

New radiator, new plastic reservoir, new t-fitting near heater core, flushed heater core. Thermostat replace within last year. New lower radiator hose.

Electric fan runs with defrost and A/C. Electric fan not kicking on. Jumped the plug and the fan runs.

I replaced the radiator temp switch, the one just above the lower hose.

New switch but same problem- fan does not turn on and lets vehicle overheat when vehicle is idling or driven at very low speeds.

Is it likely that the brand new radiator temp switch is bad?
Is there some other explanation?


Last edited by Karlinwa; 05-11-2013 at 11:59 AM..
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Unread 05-11-2013, 11:33 PM   #2
xjdantheman
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is that fan even supposed to come on other then when the a/c is on?

i thought the main engine fan was the one that handled all but when the a/c is on. is your fan clutch still in good shape?
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Unread 05-12-2013, 06:29 AM   #3
cruiser54
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So if you unplug the radiator switch and jump the harness connector there, the fan comes on?

On a side note, you shouldn't be getting that hot at an idle to require the fan's help unless it's vERY hot outside. I'm suspecting your fan clutch is bad and the mechanical fan is therefore not pulling enough air through the radiator when at a stop.
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If you own a Renix Jeep, you'll want to check this out. >

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Unread 05-12-2013, 06:30 AM   #4
cruiser54
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Quote:
Originally Posted by xjdantheman View Post
is that fan even supposed to come on other then when the a/c is on?

i thought the main engine fan was the one that handled all but when the a/c is on. is your fan clutch still in good shape?
That's what the sensor in the radiator is for on a Renix. Yours has a different set-up.
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Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-12-2013, 10:14 AM   #5
Karlinwa
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"So if you unplug the radiator switch and jump the harness connector there, the fan comes on? "

Yes, in fact I picked up a toggle switch and I cut the multi plug off the old switch to be able to wire it in while I figure it out.

To my understanding this fan is supposed to come on when the A/C is on, when the defrost is on which uses the A/C to dehumidify, and when the radiator temp exceeds 215- 220.

I had not considered that the mechanical fan clutch could be bad, I will look into that. Separate problem from the electric fan though, isn't it?

Can someone direct me to a thread on diagnosis / replacement of the clutch?

Last edited by Karlinwa; 05-12-2013 at 10:35 AM..
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Unread 05-12-2013, 11:00 AM   #6
Motorcharge
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Elec fan is supposed to kick on at 210* or when the A/C is on. Bad relay is a common problem, but if it's working with the A/C then it's not the relay.

As for the fan clutch, if you can stop the mechanical fan when the motors running then it needs to be replaced. Very easy to do, just undo the nuts or bolts (forget which) on it, slide the clutch and fan off, replace with the new one and bolt it back up. I'd suggest replacing it with a ZJ fan clutch over the stock one.

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Unread 05-12-2013, 11:52 AM   #7
cruiser54
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2 separate things. Sounds like you need a fan clutch and have a faulty radiator temp switch.
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Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-13-2013, 06:25 PM   #8
Karlinwa
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Ok I replaced the radiator temperature switch, but it is still not working. Is there another step?

I will do the mechanical clutch, it sounds like the ZJ is a direct fit?
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Unread 05-13-2013, 07:27 PM   #9
cruiser54
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Get a new fan clutch for sure. The ZJ one is quite noisy.

Please clarify what you did to test the rad switch.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-13-2013, 07:47 PM   #10
Karlinwa
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Prior to replacing the switch I used a wire to jump the connection where the switch plugs in and the fan worked fine. But replacing the old switch with a new one did not correct it.
Cruiser you recommend a stock clutch then?
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Unread 05-13-2013, 08:16 PM   #11
cruiser54
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I tried a ZJ clutch. 272310 Napa. So frickin' loud I removed it. Try stock. Either you're getting bum switches or there is no circulation around the switch.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 05-15-2013, 02:52 PM   #12
Karlinwa
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Thank you I am putting a stock mechanical clutch in today. I also wondered about if I am getting circulation, but the heater seems to be working fine.
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Unread 08-26-2013, 11:36 AM   #13
Karlinwa
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Mechanical clutch didn't help. The overheating issue was ultimately caused by a radiator reservoir not holding pressure. It had been replaced within 6 months but on the new one the threads couldn't hold the cap tight. New unit with new cap cured overheat issue.

Then yesterday with an idling vehicle dragging junk around my place the fan started working without the A/C on. Maybe the leaky reservoir somehow kept the temp below the threshold. Gauge read just a touch over 210 when it kicked on. All is good in the cooling department now.
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Unread 08-26-2013, 04:45 PM   #14
cruiser54
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Those bottles are usually warranteed for life. Use the 703-1396 cap from Napa instead of that crappo chinese one supplied with teh bottle. It even holds well on the crappo bottles.
napa-volvo-cap.jpg  
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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