Switching aux fan power from key on back to temperature

[hgeranium]

Title may be confusing, but I didn't know how to word it otherwise. The PO for whatever reason has the aux fan set to key on power. It's constantly running so long as the key is turned. It's just wired straight to the battery with a relay (that also has 2 other mysterious wires going into the wiring harness). I know it's supposed to kick on when the engine hits a certain temp. How can I re-activate this function? I wouldn't be surprised if the fan always being on is putting unnecessary strain on the alternator, considering one went bad only 6000 miles after replacing it earlier this year.

 

A few months ago, the bearing in the fan that's been in the jeep since I bought it started going out, so I replaced it with a TYC unit. A few days ago, it quit working. Luckily it's colder outside so I can run without the e-fan to figure it out but could it really just be the crap quality unit or something funky with the way it's hooked up to power? I think the original unit was an OEM Mopar unit which would definitely explain its longevity over the TYC.

 

When waiting for the TYC to come in (around July-August), I was driving it only on the mechanical fan, and the truck was consistently getting way hotter than usual. I'm pretty sure this extra heat/pressure is what did my old coolant bottle in. Sounds like a new fan clutch couldn't hurt either. I've done the paper test and it looked fine, there also isn't a TON of free-spinning of the fan when it's off but there is a little bit.

 

edit: Not sure if it's relevant at all, but the previous fan was a 97+ unit, which is what I replaced it with. TYC 620560

[87MJTIM]

You can reverse trace the PO's wiring to figure out where s/he was drawing power.  If you have not yet done so, download the 88 electrical manual pdf (here).  Use the cooling system setup to take yours back to factory.  

 

Our Renix engines have three (3) temp. sensors.  One for the gauge/idiot light, one for the ECU, and one to turn the e-fan on/off for cooling.

 

Figure out why the PO would wire the fan to run continuously.  Was it overheating? Why?  Address that problem.  Was he slow wheeling it and wanted to keep it cool?  Will you wheel it?  You could wire a switch to turn it on/off when you want it - but this would override the factory cooling fan switch. 

 

Did a PO swap radiators to later HO versions without the temp senor hole?

[hgeranium]

2 hours ago, 87MJTIM said:

You can reverse trace the PO's wiring to figure out where s/he was drawing power.  If you have not yet done so, download the 88 electrical manual pdf (here).  Use the cooling system setup to take yours back to factory.  

 

Our Renix engines have three (3) temp. sensors.  One for the gauge/idiot light, one for the ECU, and one to turn the e-fan on/off for cooling.

 

Figure out why the PO would wire the fan to run continuously.  Was it overheating? Why?  Address that problem.  Was he slow wheeling it and wanted to keep it cool?  Will you wheel it?  You could wire a switch to turn it on/off when you want it - but this would override the factory cooling fan switch. 

 

Did a PO swap radiators to later HO versions without the temp senor hole?

The fan goes straight to the battery. I haven't actually looked but I'm pretty sure I've seen the CTS on the radiator but the wires are just cut lol. I know that without the fan at all it would begin to go over that halfway mark but nothing catastrophic (until my coolant bottle busted). It's 2WD so no wheeling. Another bet is that the CTS just went bad in the radiator and instead of replacing it, the PO just hooked the fan up to the battery.

 

Thanks for the manual! I'll take a look.

[Eagle_SX4]

The easiest way to continually run the fan is to just unplug the coolant temp switch in the radiator and jump those 2 wires together. On the harness side not the switch side.

 

Check you wires down in that area and see if that connection is wired together. It is a 2 wire GM weather pack connector. I don't remember what color the wires are.