OEM Mechanical Fan Retrofit - Page 4 - JeepForum.com

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post #46 of 51 Old 07-14-2013, 05:33 PM Thread Starter
ronjenx
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Quote:
Originally Posted by Vin View Post
I was actually thinking of this thread since we're having such a hot summer in the northeast. I'm glad to see everything running well.
It's a modification I feel good about every time I drive the Jeep; on the road, or in the woods.

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post #47 of 51 Old 07-21-2013, 07:54 PM Thread Starter
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Update:

I decided to install the electric fan that is designed to be used with the mechanical fan. It has been in the 90's here lately, so I figured it's a good time to try it out.

I haven't seen much difference in engine/transmission, etc, cooling. The engine is still running around thermostat temp, and the transmission continues to run in the 90F - 130F range.


I have seen a pretty good improvement in A/C performance, though.

With just the mechanical fan, the output temp of the air from the center vents has been in the warmer half of the 20 range of acceptable performance.

For example, the acceptable output temp at 90F ambient is 48F to 69F, when all the controls are set for MAX cooling.

With just the mechanical fan, the output temp has typically been around 60F. Not great, but within the acceptable range.


After adding the electric fan, which comes on when A/C is selected, the output temp (@ 90F ambient) is in the cooler half of the range, around 52F.

So, when it was in the mid 90’s, with the high sun beating down on my black Jeep, there was a very noticeable improvement in the A/C’s ability to keep it cool inside the Jeep.

Last edited by ronjenx; 07-22-2013 at 09:20 AM. Reason: corrected 2 typos
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post #48 of 51 Old 07-21-2013, 09:32 PM
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The electric fan will have a great deal of effect on AC performance. The stock electric fan will come on low at about 240 psi and high around 305 psi.

It's scary how high condenser pressures get without proper airflow. It will shoot to over 400 psi when the PCM shuts off the compresser based on info from the pressure transducer. If it continues to climb a safety relief valve or fuse will blow, hopefully before a line or fitting.

Jeep recommends shutting the AC off on fan clutch equipped vehicles at low speed, when you need it most.

Your observations show the benefits of cooling air independent of engine speed. Seems like guys dwell on the engine and trans temps and ignore condenser pressure; when it's 120* out here and I go for a test drive I carefully watch condenser pressure, I've seen systems blow and it's not fun. AC systems protect themselves by shutting off the compressor at high pressures and outlet temps rise, older systems run at high pressures can leak or fail.

Unbeknownst to you your AC pressures were most likely approaching 400 psi, I'm glad you added the electric fan. I find Jeep shuts off the compressor at 41* and back on at 46* EVAP temp, this keeps the evaporator from freezing or creating excessive water formation on humid days, we shoot for 37* to lower outlet temp a bit. This is the reason the resistor mod works. The 11' up auto air are a whole new ball game.

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post #49 of 51 Old 07-21-2013, 09:44 PM
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That's interesting to note about the AC, that was something that I have never heard anyone explain. My assumption would be that this is really only an issue at slower speed right? My temps remain great when I am cruising at freeway speeds, though I have never monitored the ac line pressures. I only see issues with temps when I run at the slower speeds.

I will add the electric fan to my list. I was debating whether I needed it or not.
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post #50 of 51 Old 07-21-2013, 11:09 PM Thread Starter
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Quote:
Originally Posted by VEGASROBBI View Post
The electric fan will have a great deal of effect on AC performance. The stock electric fan will come on low at about 240 psi and high around 305 psi.

It's scary how high condenser pressures get without proper airflow. It will shoot to over 400 psi when the PCM shuts off the compresser based on info from the pressure transducer. If it continues to climb a safety relief valve or fuse will blow, hopefully before a line or fitting.

Jeep recommends shutting the AC off on fan clutch equipped vehicles at low speed, when you need it most.

Your observations show the benefits of cooling air independent of engine speed. Seems like guys dwell on the engine and trans temps and ignore condenser pressure; when it's 120* out here and I go for a test drive I carefully watch condenser pressure, I've seen systems blow and it's not fun. AC systems protect themselves by shutting off the compressor at high pressures and outlet temps rise, older systems run at high pressures can leak or fail.

Unbeknownst to you your AC pressures were most likely approaching 400 psi, I'm glad you added the electric fan. I find Jeep shuts off the compressor at 41* and back on at 46* EVAP temp, this keeps the evaporator from freezing or creating excessive water formation on humid days, we shoot for 37* to lower outlet temp a bit. This is the reason the resistor mod works. The 11' up auto air are a whole new ball game.
Your previous comments about the A/C were in the back of my mind when I decided to try the addition of the electric fan. I didn't monitor the pressure in the system. I assume all was well because the outlet temps were within limits, and there was no indication the system was shutting down.

The electric fan will serve as a backup to the mechanical fan, in addition to it's benefit to the A/C system.
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post #51 of 51 Old 09-25-2015, 01:07 PM
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What a great thread! Thanks to Ronjenx for all the research, wrench time and postings. Since new, even with a trans cooler I've felt my '09 JKUR just had silly underhood temps that could be ameliorated a bit with a mechanical fan setup. After reading Ron's report I was concerned re: A/C pressures. Looks like there's a plug & play setup that kills both birds. Thanks again!

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