JZLAJeep Posted July 7, 2023 Share Posted July 7, 2023 On our last wheeling trip, the Comanche was having overheating issues. Nothing that couldn't be remedied by slowing down and giving it occasional breaks, but definitely annoying. It's an '89 Renix with just a mechanical clutch fan. The '94 and '95 High Output XJs never ever overheat, and they have an electric fan along with the mechanical fan. So I'm looking to add an electric fan to the Comanche. I have an electric fan from a '98 XJ, just need to install and wire it. Does the Renix hardware include any fan wiring like the High Output does, or is my best bet just to add an aftermarket electric fan switch and relay? I'd just hate to wire in a bunch of aftermarket stuff and then find out that the stock ECU supports an electric fan. Link to comment Share on other sites More sharing options...
TurboedMJ Posted July 7, 2023 Share Posted July 7, 2023 Have you recently flushed the coolant? Does it have air in the system and need burped? I got my coolant flushed by a shop and they didn't burp it right, ten minutes down the road it was overheated. Put more coolant in it (until the pressure tank was about half full). Before that flush and since I filled it up it has always ran rock steady at 150* and I drive hard. Link to comment Share on other sites More sharing options...
JZLAJeep Posted July 7, 2023 Author Share Posted July 7, 2023 Yes, we flushed it a few months ago and it's definitely burped. It never overheated before or since driving around town, it just needs a little more help offroading, when we're climbing gnarly grades with not a lot of air coming through the radiator. Although i am impressed that it runs at 150, all three of our jeeps like to run about 190, which makes sense since the stock thermostat is a 190. Link to comment Share on other sites More sharing options...
TurboedMJ Posted July 7, 2023 Share Posted July 7, 2023 10 minutes ago, JZLAJeep said: Although i am impressed that it runs at 150, all three of our jeeps like to run about 190, which makes sense since the stock thermostat is a 190. I am not sure why mine runs so much colder, maybe my temp gauge is shot😅 Anyways, the p.o. of my mj wired a switched fan directly to the battery and placed that in front of the intake manifold. Seems simple enough, not sure about a factory option tho. Link to comment Share on other sites More sharing options...
acfortier Posted July 7, 2023 Share Posted July 7, 2023 150 is definitely way too low--might want to double-check that. My '91 seems to run about 210*, default thermostat is a 195*, so somewhere in that range seems to be correct for our Jeeps. I had assumed all 4.0 MJs came with an e-fan, even the Renix ones? Or was that part of the "heavy duty cooling" option? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 7, 2023 Share Posted July 7, 2023 Sounds like it might just need a new Mopar 195* thermostat. Perhaps now it has a failed one or it's been removed. Link to comment Share on other sites More sharing options...
Gojira94 Posted July 7, 2023 Share Posted July 7, 2023 I'm in the same boat, though I'm not on the road yet. My engine harness has a single ground loop at the left fender well but no fan control relay, fan motor or radiator temperature switch (C243, C244, C245) wiring in it or a diode assembly for A/C turn-on of the fan signal. The 88 electrical manual (p.40) says the ground point for the "heavy duty cooling-4L (option)" is at G106. Maybe that's the additional ground loop shown in the harness diagrams with the additional cooling option. I'd swear I read something before that showed the ground point numbers/ locations but I can't find it at the moment to confirm. I picked up a temperature switch (Std Motor Products TS258/ Duralast SW594) to go with a late HO radiator that has the cooling fan switch threaded boss in it. The later electric fans with more blades will have a different connector than the early ones for Renix, but that probably won't matter for building your own setup based on the electrical manual diagram. Just need a 190* temp switch either in the radiator or HO t-stat housing to make the signal, a 40A relay, fan assembly, power & ground. From what I'm reading, there is no signal to/ from ECU in this arrangement for '88. Link to comment Share on other sites More sharing options...
pizzaman09 Posted July 9, 2023 Share Posted July 9, 2023 The Comanches with AC has the electric fan as well. My truck has dealer installed AC which added the thermal switch and relay for the electric fan. I recently changed my switch and the fan now works perfectly. On a hot day my truck at idle will creep up above the 195 thermostat to 210 or so, particularly at idle. Mine is a 1990 Renix truck. Should be easy enough to do, there are after market temp sensing kits, or you can wire it to a switch. Link to comment Share on other sites More sharing options...
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