88 Renix Elec Fan

From what i understand, the electric fan is supposed to turn on at 190f as well as when the A/C is going.

My A/C has never worked since i got the jeep 2 years ago. Turning the incab controls to A/C Max while running does not turn the fan on.

Cooling fan switch is brand new.

Using a Jumper lead from the battery to the fan forces it on so i know the fan is functioning. going through a couple How to's for the fan system i have located the fan relay. i am able to Jump the fan connecting points 1 and 4 on the relay. The guides are saying i should be getting a voltage read out on point 2 but while testing it i only get a positive read out on point 4.

Its getting warmer and i would like to get my fan to function correctly without having to fiddle with a toggle switch. any helpful tips are appreciated.

Thanks again!

If you jump the two wires going to the thermal switch in the lower left of your radiator your aux fan should come on.

The thermal switch is in the lower left of the radiator, the coolest place in the system, the temperature gauge sender is in the top rear of the head in one of the warmer places in the system. My in dash gauge usually reads well over 212F when the aux fan comes on.

Mine comes on about 202*. FWIW, the fan will not come on with AC selected if you have no charge in the system unless you bypass the low pressure switch connector at the drier.

cruiser54 said:

Mine comes on about 202*. FWIW, the fan will not come on with AC selected if you have no charge in the system unless you bypass the low pressure switch connector at the drier.

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Changed Cooling fan and A/C relay as well as Low pressure switch on the dryer in hopes that even with no pressure it would still allow the fan to come on while the A/C of off.


I am able to bypass the switch and manual engage the clutch while the motor is running. doing so now will turn the electric fan on when A/C is selected in cab.

I am still boiling over before my temp gauge even reads 200 and the fan is still not turning on.

Could i be boiling over and having fluid come out the reservoir even before i hit the 195 for the fan to kick on? and if so any ideas on where to start my trouble shooting? unless i let it boil over there is no leaks, heater core is good, blows hot air, clutch fan is new from last fall. The fan shroud is broken on the top of the clutch fan but i cant imagine that it would have this much of an effect. i do have a replacement shroud to put on, was hoping i would need a new radiator by the time i put it on so i didnt have to take it all apart for nothing.

Thanks again!

You may have a blown head gasket making you think it's boiling over.
Water don't boil until 212 deg's, when your system pressurizes the water temp is 220 but won't boil because it's under pressure.

langer1 said:

You may have a blown head gasket making you think it's boiling over.
Water don't boil until 212 deg's, when your system pressurizes the water temp is 220 but won't boil because it's under pressure.

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instead of say boiling over but i should have said, spewed from my crappy renix reservoir way before the the red line and just before it would read 200

Have you replaced the turtle and cap yet?

the reservoir looks like its been replaces, maybe right before i got the jeep about 2 years ago. i grabbed a better looking cap from the JY a few months ago and threw it on. but no i have not replaced both new from a autoparts store yet.

Your "reservoir" is up on the firewall on the pass. side correct ? It has a black plastic screw on cap ? The way you describe it, water is "boiling" into and out of that bottle when it get's hot ?

If so, how does coolant spew from it ? It should be a completely sealed system.

It's been a while since I had one in my hands but that's what I recall from my fuzzy memory.

jeannies_driver said:

Your "reservoir" is up on the firewall on the pass. side correct ? It has a black plastic screw on cap ? The way you describe it, water is "boiling" into and out of that bottle when it get's hot ?

If so, how does coolant spew from it ? It should be a completely sealed system.

It's been a while since I had one in my hands but that's what I recall from my fuzzy memory.

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yeah, its the reservoir on the firewall. the coolant is coming out of the cap. it seems no matter how tight or how hard i try and position the cap it never seats well(tried with a few caps).

Elcapitano said:

yeah, its the reservoir on the firewall. the coolant is coming out of the cap. it seems no matter how tight or how hard i try and position the cap it never seats well(tried with a few caps).

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Go to Napa and buy this cap: 703-1396. Good chance your problem will be solved.

Yeah, my cap looks nothing like that one. ill check it out tomorrow. make makes this one better then a OEM style cap?

Elcapitano said:

Yeah, my cap looks nothing like that one. ill check it out tomorrow. make makes this one better then a OEM style cap?

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Fits better on the threads. Has a lower profile to keep it from rubbing the hood. Holds a higher pressure. It's not chinese.

Note from DJ
The new cap will probably not fit down into your pressure bottle easy. Don’t be concerned if it doesn’t, just keep pushing down and turning it will fit. The openings in some of the pressure bottles are inconsistent in there ID.

djgrayxj said:

Note from DJ
The new cap will probably not fit down into your pressure bottle easy. Don’t be concerned if it doesn’t, just keep pushing down and turning it will fit. The openings in some of the pressure bottles are inconsistent in there ID.

Click to expand...

Note to Self
Will remember

djgrayxj said:

Note from DJ
The new cap will probably not fit down into your pressure bottle easy. Don’t be concerned if it doesn’t, just keep pushing down and turning it will fit. The openings in some of the pressure bottles are inconsistent in there ID.

Click to expand...

Good catch DJ. Yep, push it into the opening and then screw it on.

yeah, i put more then enough pressure on the cap it self for it to seat down. ill get the cap tomorrow and hope that its not puking coolant. maybe my fan will come on after that ?

You'll probably be fine with the new cap.

When my 88 spewed it was a partially plugged radiator. The reduced amount of coolant moving through the radiator never did kick my fan on. My guess is the coolant was cool coming out of the radiator, but the flow was reduced. It would overheat in the head and block, then spew. My in dash temperature gauge would also spike.

I noticed my top radiator hose was hard as a rock and actually looked like it was swelling as the coolant backed up and built pressure, trying to make it through the old partially plugged radiator.

After I put in a new radiator, I could squeeze the top hose together with my fingers, with the engine running and at operating temperature.

The cap on the surge tank is a pressure cap, just like any other radiator cap, it vents around 15-16 PSI. But the way it the system is engineered, it should only vent air and not coolant.

I always fill my surge tank/reservoir a little more than half way, if you fill it to the top it can also spew.

The surge tank threads and the cap, mostly after market, are often a sloppy fit. Some after market caps you can actually put a hose clamp around the cap and squeeze it a little smaller and get a better fit. The threads for the cap aren't the seal, the cap has a gasket in there. If the top of the surge tank opening is not flat it may not seal. A little work with a fine file and a little sand paper can usually take care of that.

For a few years there was a rash of poor quality control on the after market surge tanks, most all of the auto parts suppliers were getting the same crappy quality. It took me three tanks to eventually get one that lasted.

If the vent in the cap gets stuck or sticky, by build up or that crusty looking stuff, soaking it in a glass of vinegar over night will clean out the little plunger and spring and likely it will work like new.

Flushing the radiator may or may not help. There may be so much crud in there, no amount of flushing will dislodge it all. And if you ever do get it clean, the copper in the radiator may be eaten up so much it crumbles and/or springs pinhole leaks.

Eagle an old time member told me the life expectancy of a radiator is around seven years, he never steered me wrong that I can remember. Anybody ever hear from Eagle lately?

If a new cap don't solve the problem I would pressure test the system.
You can also find a leak if there is one by reading the spark plugs, look for one that looks supper clean, like new and thats where the leak is.

I have run my 78 cherokee without the fan and it didn't overheat.
Some XJ's don't have an electric fan if they don't have air.