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940 terrible air conditioning performance!!!!

hunterkent

hunterkent

New member
Joined
Jan 31, 2013
Location
salem,oregon
so my 91 940 has the following
brand new A/C pump
new dryer
new orifice
new o rights all through the system
condenser has been flushed.
new oil
then it was all converted to r134 and charged.

the system kicks on and the pump works fine--small line gets way to hot to touch and the condenser gets nice and hot so i know theres flow there

the issue is that it doesn't blow cold...i mean the air is chilled some but not anywhere near what it should be even on full cool driving 55 down the road.. after a long drive with it on the cab will get down to around 70 or so but not any cooler. after that drive.( about 30 minutes straight with it maxed out) i popped the hood and the lines were soaking wet and seemed pretty quite cold, including the dryer, but the air still wasn't amazingly cold. :-(

what could be causing this ?

i know i have a vacuum leak cause the damn thing wont change where the air come out of if you mash it but I'm pretty sure nothing involving the temperature is controlled by vacuum......right ?

and yes i have a set of manifold gauges and it has plenty of pressure ( not to much) cant say about the high pressure side cause i can find the high side port. but the charge is up to par with brand new r134A
 
So, I'm not an ac guy and I've never converted one, so toss this aside when you get some empirical opinions, but...r 134 is less effective than r12, and systems designed for it have to be "bigger" for the same net cooling. A converted system cannot possibly cool as well as it could have done with r12. I would love to hear some workarounds, like bigger coils that fit or whatnot, or (again, I haven't done it myself) hear somebody tell us how yours can be better. But the science of the two refrigerants is not on your side with the existing parts.
 
Install a variable orifice valve for R-134A. Charge with Dura-cool. It will then blow as cold as the R-12 it had originally.

Alternatively, install a variable orifice tube, charge with R12 or R22 (less leak prone, and I think still legal), enjoy freezing temps.

Hope you didn't get PAG oil mixed in with the mineral oil leftover from R12. Enjoy acid and deadly black goo now spread throughout.
 
Dicktater said:
hot water control valve for the heater core.
Click to expand...

This for sure. Fought mine for some time and found the valve wasn't closing completely. Fixed that and the vent temps dropped 8-10 degrees in the driveway.

Curious on the Duracool and variable orifice though. Mine's never done all that well, especially sitting in traffic. Cruising on the highway at 100* out it's sitting around 50-55* at the vents, where Gwen's R is doing high 30's. Dunno exactly what mine did on R12 but it was definitely colder...until the hose split.
 
I was just going to post something similar after "fixing" my ac this week. My ac was converted to R134 at a Volvo dealer before I owned the car and I always worked great. The compressor took a dump in 2008 so I replaced that and it still worked well after that. 2 years ago I had a leak in the system, took forever to find but finally got it fixed. Then the system would hold pressure and the compressor would kick on but the air coming out of the vents wouldn't even get cool, just blew out hot air. I thought my orifice tube was clogged from all the uv dye I put in the system so I opened everything up, flushed my evap and condenser, replaced the orifice tube and the drier. A done of dye gunk came out so I figured that was the problem for sure so I closed it up and put a vacuum on it for over an hour. The vacuum held so no leaks and it took a full can of R134 until the compressor was engaging steadily and not cycling on and off quickly. After a few minutes of running I can feel that the line going into the firewall is freezing cold yet I'm still getting warm outside temp air coming through the vents even after driving around. Any thoughts? Could this possibly be the heater control valve too?
 
so you were right the valve didn't have any vacuum so it was at full flow... so i zip tied it shut. now after it runs for a bit at 65 degrees outside i get 38-42 degrees out of the vents. it doesnt feel very cold even still...my 87 f-150 feels 10 times colder to me and its a r12-r134 retrofit. so whats the story with this duracool ? is it worth draining it all out and charging it again ?
 
also i have heard mixed things on the variable orifice...i guess i dont understand the purpose of the orifice enough to see why it work better? and ac guys wanna chime in and give me some wisdom...i just want this ac cold again lol
 
You're complaining about 38-42* at the vents? That's WELL within spec for higher ambient temps. Keep in mind if it goes much lower the evap. may start icing up. See what it does when it's warm, and also see what kind of difference it makes with a fan in front of the radiator to get some airflow thru it.
 
well i fixed the vacuum leak so all the air actually comes out of the dash vents now so that helped a ton. ill see how cold it stays when it gets hot again. if it doesn't stay cold enough i might swap it over to duracool and put the new orifice in. i just want it to work as good as my truck. you would think 91 volvo air conditioning could work as well as 87 ford air conditioning
 
I certainly wouldn't complain about 38 degree vent temps. Also take into account that a 940 has more interior space than a single cab ford truck so it will take longer to cool off...
 
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