Dando Posted July 21, 2014 Share Posted July 21, 2014 So yesterday I was driving around a lot. My temp gauge reached just shy of 240ish. When I stopped and checked under the hood my aux fan wasn't running. The wiring read 12v while the engine was that hot and then once it cooled off again the wiring read zero so I assume the switch is working properly. My guess is the fan motor itself is shot after 25 years. Running the heat got the engine to cool down quickly and then in the early nighttime I took it out again and it didn't get that hot after completely removing the fan from the truck. Is the lack of a functioning aux fan truly capable of causing me such cooling issues? It seemed like when the ambient temp dropped at night that truck stayed cool. Can the electric fan make that much of a difference in the coolant temp? Oh and my coolant pressure tank and cap are both brand new, not seeing any coolant leaks from anywhere on the truck. Link to comment Share on other sites More sharing options...
sloride Posted July 21, 2014 Share Posted July 21, 2014 Is the lack of a functioning aux fan truly capable of causing me such cooling issues? Basically, yes it could be causing you cooling issues. There's other factors involved such as the age of your coolant or if you're using any, performance of your water pump, to your thermostat to name a few variables. I'm in the process of trouble shooting my aux fan troubles. My problem was the switch. The FSM has a diagnostic procedure to help with that. You didn't say you tried hot wiring the fan motor to see if it still works. My fan is the age and still works like a champ. Did you check your relay? It's on the drivers side fender. Clean your relay contacts? Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 21, 2014 Share Posted July 21, 2014 If the E-fan is not working, only 50% of your radiator has any drawn air moving through it. Yeah, makes a difference. Link to comment Share on other sites More sharing options...
Dando Posted July 21, 2014 Author Share Posted July 21, 2014 Yes I did try to hard wire the fan with jumpers to the battery, no life out of the fan. Fairly certain the fan motor is bad. Coolant at the moment is straight water. Brand new 195* thermostat this am with new 91+ housing. Unsure of age of the water pump, but seems to be pumping water around. I have cleaned and dielectric greased every under good connection previously, replaced the relay with a know good one as a precaution. The only part of all of this that won't be new seems to be the fan switch, I tried calling my local auto parts store and they can't find it on the computer does anyone know the p/n as I would change it for reassurance. Link to comment Share on other sites More sharing options...
yxmj Posted July 21, 2014 Share Posted July 21, 2014 If you hard wired the fan and nothing happed........I would look there first..... :dunno: Link to comment Share on other sites More sharing options...
Dando Posted July 21, 2014 Author Share Posted July 21, 2014 I plan on replacing it but the part won't be delivered till Tuesday, just figuring why not replace some other stuff while it's easy to get to with the fan already out of the way. Link to comment Share on other sites More sharing options...
sloride Posted July 21, 2014 Share Posted July 21, 2014 Okay, you jumped the fan. I have to ask if you checked correct polarity when you did that. The reason I ask is because the first time I had trouble with my fan was about 1997 and I jumped the fan and got nothing, then it dawned on me I'm dealing with DC not AC. I switched the jumper polarity and it worked. CarQuest has the switch for my '88 part number 53-13892 Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 21, 2014 Share Posted July 21, 2014 If you are bench testing a fan motor (simply applying 12VDC at the motor connector w/o any control circuitry attached), polarity doesn't matter. If the motor is good, it will just run in the opposite direction if polarity is reversed. Link to comment Share on other sites More sharing options...
Dando Posted July 21, 2014 Author Share Posted July 21, 2014 All I did was run two pieces of 14 ga wire into the disconnected fan connector on the fan side from the positive and negative of the battery. I got no movement in the fan. Link to comment Share on other sites More sharing options...
sloride Posted July 21, 2014 Share Posted July 21, 2014 I thought it should run in any direction since it's DC. It figures I get a DC fan that only turns one way. Link to comment Share on other sites More sharing options...
yxmj Posted July 21, 2014 Share Posted July 21, 2014 If you are looking at the JY for a fan...look for one from a 97-01 xj.....direct bolt in replacement and more air flow.....they look like this :thumbsup: Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 21, 2014 Share Posted July 21, 2014 If you are looking at the JY for a fan...look for one from a 97-01 xj.....direct bolt in replacement and more air flow.....they look like this :thumbsup: ^^that except for the wiring harness/plug. Link to comment Share on other sites More sharing options...
Dando Posted July 21, 2014 Author Share Posted July 21, 2014 I actually already ordered one for the truck, the part number is the same though amongst the years (just in their computer) according to the parts counter guy. Link to comment Share on other sites More sharing options...
Dando Posted July 21, 2014 Author Share Posted July 21, 2014 Ok so after changing thermostat, still have no aux can installed. After driving 30 minutes and ambient air temp being 85* the truck gauge sits here: After sitting running at idle after the drive the gauge sits here: Now my multimeter doesn't show the aux can being triggered till my gauge reads just below the red. And when the gauge is at about 218*-220* there is no power for the fan. Is it possible being I swapped clusters that my sending unit for the gauge needs to be from a different year to match the cluster? Could my gauge just be reading improperly? It's a new sender for a 1990 4.0L but I am unsure of what year the gauge cluster came from. Any ideas? Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 21, 2014 Share Posted July 21, 2014 Your gauge cluster looks to be an 86 model year. And yeah, it matters. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 21, 2014 Share Posted July 21, 2014 The aux fan on the HOs comes on when the coolant temp reaches ~230 degrees. This is normal. ASSume it's the same for the Renix. Link to comment Share on other sites More sharing options...
Dando Posted July 22, 2014 Author Share Posted July 22, 2014 If this cluster is from an 86, which it could be, is it worth keeping as the 86 did not come with the 4.0L? Link to comment Share on other sites More sharing options...
1989 Eliminator Posted July 22, 2014 Share Posted July 22, 2014 Could it be that you need to backflush your radiator and heater core? That helped mine a lot. Link to comment Share on other sites More sharing options...
benjy_26 Posted July 22, 2014 Share Posted July 22, 2014 1989 Eliminator is right. If you havent flushed your system, it would be a good idea. Do you have access to a laser thermometer? I kept chasing overheating issues in one of my vehicles until I zapped the T-stat housing and radiator. Turned out I had a bad gauge. Link to comment Share on other sites More sharing options...
Dando Posted July 22, 2014 Author Share Posted July 22, 2014 I flushed the radiator a couple months ago as a precaution before summer started up so I feel it's good. I don't personally have a thermo laser but I am pretty sure I will be able to get my hands on one pretty easily, good idea. Link to comment Share on other sites More sharing options...
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