closed cooling system conversion questions

ok guys here goes, i have converted my 88 xj's cooling system to the open style system with 3 core gdi a 91 or newer water outlet which houses the auxillary cooling fan sensor and put a 16lb rad cap and overflow tank on, my problem is as follows. the auxillary fan wont turn on automatically when i start to get too hot, if im at say 220 or 230 degrees it doesnt come on,if i turn my A/C on then the fan fires up like it should, however if i turn the a/c off and the jeep is still at 220 the fan will stay on until the jeep cools down, so the cooling fan wont come on by itself but will stay running until the radiator cools down, i have replaced the fan relay, i have checked for continuity when the fan sensor is cold and for when it is hot to see if its working, it appears to work but when i switch to check for resistance when the rad is hot the ohmeter is saying .65 resistance, anybody out there ever have this prob? I know guys usually hook up a switch to turn it off and on but i dont see any reason since the proper items are available to hook it up to do so automatically, sorry for the long post and TIA

Joe

Sigh ... Here we go again. This is why I recommend against doing this swap.

The '88 uses a thermal SWITCH in the radiator to control the aux fan. The sensor you put in the thermostat housing is probably the OEM sensor for a 91+ XJ, right? That is not a switch -- it's a temperature sensor. It doesn't go from OFF to ON -- it's a varaible resistor.

The hassle with this conversion is finding a SWITCH that will fit the opening in the thermostat housing. A long time ago someone claimed he had found a Honda part that would work ... but then he was unable to provide a part number. Someone else claimed they had a Jeep part that would fit ... until he researched and discovered that what he had was a ZJ temperature sensor that had failed and wasn't working correctly.

Try running a search to see what others have done. The simple answer is to wire a toggle switch to the aux fan relay and control it manually.

Do what this article describes. that what i am planning to do:-
http://www.bigoffroad.com/pages/bigpages/bigtech/xjfan.htm

Ravi

THANKS GUYS THATS EXACTLY WHAT I WAS LOOKIN FOR

That modification makes no sense whatsoever (IMHO).

The old-style fan already has a relay, so now your just using a relay to switch a relay. The '91+ sensor is still a variable resistor sensor, not an ON/OFF switch, so I don't see how this makes the aux fan work any better than just running that connector directly to the new temp sensor.

If you try it, please let us know if it works. It shouldn't.

This was posted on my local off-road board recently. I have no idea if it is true or not so a little DD is required.

Cheers!

"Renix / closed-to-open system conversion update!

If you'll use a late model thermostat housing intended for the factory fans switch you can use a fan switch for an '81 to '82 corvette with a 350 to control your electric fan! (The late style thermostat housing can be seen here. I have a drain petcock installed in the sensor port.)

Just ask for Borg Warner part #TFS19 or Niehoff part #DR137XL.

All you need to do is plug it into the late model thermostat neck, extend two wires to where your original fan switch plugged in using same method as below.

This switch turns the fan on at approximately 215 and off around 195.

Full Credit for finding this out goes to Avanteone (John) who posted this information on J.U. The actual text of his post is buried somewhere in the J.U. archives and is listed here only for informational purposes. No credit is claimed for finding this information! Many of us beat our heads against the counter at several auto parts houses trying to find exactly what John figured out! For more details, please go to J.U. and search for his user name and this subject."

the best and cheapest fix is to go to auto zone and buy a 15$ adjustable electric fan control. It comes with a sensor that you stick in the radiator cooling fins. you can adjust to come on whenever you want to. Why would you pay all that money trying to use the orginal wiring and sensors?

BEEN THERE DONE THAT WHEN I TRIED ELIMINATING MY MECHANICAL FAN WITH A THERMO SWITCH CONTROLLED ELECTRIC FAN, I STARTED GETTIN NERVOUS WHEN THE FAN WOULD RUN FOR 30 MINUTES OR MORE AFTER TURNING JEEP OFF, didnt want a dead battery I COULD HAVE WIRED IT TO BE HOT ONLY WHEN IGNITION SWITCHED TO ON BUT SCRAPPED THE IDEA CAUSE THE FAN DIDNT MOVE ENOUGH AIR, SORRY FOR THE CAPS
JOE

Bender said:

This was posted on my local off-road board recently. I have no idea if it is true or not so a little DD is required.

Cheers!

"Renix / closed-to-open system conversion update!

If you'll use a late model thermostat housing intended for the factory fans switch you can use a fan switch for an '81 to '82 corvette with a 350 to control your electric fan! (The late style thermostat housing can be seen here. I have a drain petcock installed in the sensor port.)

Just ask for Borg Warner part #TFS19 or Niehoff part #DR137XL.

All you need to do is plug it into the late model thermostat neck, extend two wires to where your original fan switch plugged in using same method as below.

This switch turns the fan on at approximately 215 and off around 195.

Full Credit for finding this out goes to Avanteone (John) who posted this information on J.U. The actual text of his post is buried somewhere in the J.U. archives and is listed here only for informational purposes. No credit is claimed for finding this information! Many of us beat our heads against the counter at several auto parts houses trying to find exactly what John figured out! For more details, please go to J.U. and search for his user name and this subject."

Click to expand...

Here is the thread:-
http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=347642&highlight=corvette

Toggle switch the fan. With an upgraded rad and a 185 t-stat I usually run about 185-190*. I don't use the fan 'til I reach operating temp and that's only in traffic or on something steep.