problem with radiator fan please help

[02blue]

Blower relay and fan relay are same part number so that was a good swap.

Wonder if the relay isn't getting a signal from the temperature sensor.

 

[JeepJeepster]

Just as an fyi incase youre curious. May already know this. The A/C turns on the low speed fan. I do not believe it will turn on the hi speed unless the engine calls for it.

I would like to know what replaced the relay that pre-04 kj's have on the fender? I feel like Ive read it before when tjkj posted something about it but I cant remember. This makes me want a mechanical fan pretty bad. Electric fans have their place but I like a backup.

The setup on my 5.9 zj is great. It has a low speed sensor in the top radiator hose and a high speed sensor in the lower radiator hose. When the coolant gets to a certain temp the upper hose kicks the fan on low. When the temp gets too high coming out of the radiator in the lower rad hose it kicks the fan on high. The A/C also kicks it on low with another sensor in the a/c coolant hose. Its idiot proof. Doesn't involve the computer at all.

 

[TwoBobsKJ]

This makes me want a mechanical fan pretty bad. Electric fans have their place but I like a backup.

Jeepster, didn't you say once that you have the extended shroud on your KJ? If so all you need to get is a Hayden fan clutch (available at Summit Racing, O'Reilly's, other places) and the nylon fan from Mopar.

If you don't have the shroud it's available on eBay, plus the parts mentioned above and you're in business. It's literally a 30 minute job to install the shroud and mechanical fan.

Now, back to the original poster's question...

Bob

 

[JeepJeepster]

Yup, i do. Only reason ive not done it is from worrying about hurting the already horrible mpg. She struggles to get 17-18.

 

[TwoBobsKJ]

Yup, i do. Only reason ive not done it is from worrying about hurting the already horrible mpg. She struggles to get 17-18.

There was virtually no change when I did mine. My '03 came with standard cooling and I upgraded it to the HD system. MPG's stayed the same.

Bob

 

[tjkj2002]

Just as an fyi incase youre curious. May already know this. The A/C turns on the low speed fan. I do not believe it will turn on the hi speed unless the engine calls for it.

I would like to know what replaced the relay that pre-04 kj's have on the fender? I feel like Ive read it before when tjkj posted something about it but I cant remember. This makes me want a mechanical fan pretty bad. Electric fans have their place but I like a backup.

The setup on my 5.9 zj is great. It has a low speed sensor in the top radiator hose and a high speed sensor in the lower radiator hose. When the coolant gets to a certain temp the upper hose kicks the fan on low. When the temp gets too high coming out of the radiator in the lower rad hose it kicks the fan on high. The A/C also kicks it on low with another sensor in the a/c coolant hose. Its idiot proof. Doesn't involve the computer at all.

'02-'04 KJ's use a 1 speed fan with the relay under the battery,'05+ KJ's use a 2 speed fan with a high and low relay in the under hood fuse box.In both cases the fan is controlled by the PCM.




If you want to add the mechanical fan all those clutch's specific to the KJ do not fully lock until about 230 degree's as it's considered a AUX cooling fan on a KJ.Personally if I was going to do this I would get the adapter to use a non-clutched flex fan.


The flex fan I would use....................

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A composite flex fan found at Summit or JEG's and only about $22.I've used this type of flex fan before to meet rules when I used to mud drag race.

 

[TwoBobsKJ]

If you want to add the mechanical fan all those clutch's specific to the KJ do not fully lock until about 230 degree's as it's considered a AUX cooling fan on a KJ.

I went with the Hayden HD fan for just that reason - specs say it locks at 190 or 195 degrees. Got that tip from the CRD guys over on LOST.

Sure like the flex fan idea though - and with Summit Racing right up the street I may go take a look at one of those composite fans...

Bob

 

[JeepJeepster]

Guess the late 04's got the dual speed fan? Or is that b/c i have the fan that came with the towing pack? Mine has the two relays and no relay under the battery.

I wouldnt want the hd clutch or a clutch-less fan. I would only want it to keep my engine from over heating in an emergency. Say im sitting in traffic and my electric fan craps out. I could at least drop the ****** in n and keep the rpm's up to move some air.

 

[tjkj2002]

Guess the late 04's got the dual speed fan? Or is that b/c i have the fan that came with the towing pack? Mine has the two relays and no relay under the battery.

I wouldnt want the hd clutch or a clutch-less fan. I would only want it to keep my engine from over heating in an emergency. Say im sitting in traffic and my electric fan craps out. I could at least drop the ****** in n and keep the rpm's up to move some air.

Could be possible late '04's got the new setup but all the '04's I've worked on have had the relay under the battery and single speed fan.


As far as those non-clutched flex fans those plastic ones weigh next to nothing and about say 1500-2000rpm's they pull almost zero air so the reduction in mpg's and WP wear is a non-issue.

 

[sebastien7]

Chris90 did you ever figure out the issue? My wifes 2003 V-6 has the exact same issue. Fan only comes on when a/c is on. Overheats while idling after long drives (I think the wind cools it enough while driving).