Divorce Aux Fan from AC

[flint54]

Well, I tried to search, because I think I've read this here before, but

our search tool will not permit only two characters, like "AC" which is

frustrating.

 

Now that I have abundant cooling, I would like my LH aux fan to NOT come

on automatically when AC is running. Want it temperature-driven only,

at 220 deg. My RH aux fan triggers 50% at 205 deg and 100% at 210 deg.

 

Being no electrician, I can follow black lines on a schematic all day long and

still not be able to point to the part on vehicle.

 

What I actually want is a trial separation rather than divorce, who knows where

(if) I can easily do this? Perhaps even add a switch so they can still date

each other? Thanks!

[JeffN]

If the aux fan is not on when your A/C is on your high side pressure will go thru the roof if you aren't moving fast enough.

Sometime the engineers get it right.

[flint54]

Thanks for your speedy reply! To make sure I understand you correctly,

you are telling me that that the aux fan is required to run so as to pull air

through the condenser, or else the refrigerant pressure can become excessive?

 

I surely do not want to blow out the AC lines (since they're pretty corroded

anyways), but I have to wonder how high it can get (without fan), how high

is excessive, and whether the system has a high side cutout (or bypass relief?)

like many systems have cutout for the low side being too low.

 

Since a lot (most) of my driving is at high speed, I was thinking the fan doesn't

need to always run, but if moving slowly I could switch back on the relationship.

I really doubt I need that fan running when I'm moving at 75mph (and would like

to shed load, however small, when I can)

 

Found this:http://jeep.zerok.ru/files/XJ1984-1991/acsystemdiagnosis.pdf

 

which suggests high side could reach >350 psi on very hot day, but for me I

should expect to not exceed 260-270 normally. Suppose I could just sit without

the fan running and watch a high side gauge to see what it does?

[JeffN]

Well, we had a dodge full size truck with a v6 (stupid) in it, he had it to 4 shops for low power until it came to us.

One of our techs drove it alot trying to get it to act up and never could.

Then one day it was unusually warm and when he drove it he turned the A/C on, vehicle was suddenly low on power.

He put my Snap-On Modis in it to record the data stream as he drove it, got back to the shop and reviewed the data and found the high side pressure was almost 500lbs!!!

He then determined that the aux fan was not working with A/C on and even on highway speeds the truck drove like a turd.

He put a new aux fan in and the truck came alive.

 

The compressor was working so hard it was trying to stall the engine in the truck, so when I say the fan should run factory it is because I truly believe the load from the A/C not being properly cooled would be much more than just a little bit more the electrical system would have to put out.