I was wondering (btw it's not good when I start doing that) if I took the condenser out of a 15 passenger van and put it on an 93 F250 if I would end up with lower high side pressure?

I have had the A/C redone twice by shops that are known to do really good work, just not on my truck. With both shops the tecs couldn't figure out why the high side pressure was so high.They both replaced every piece of the system so there was no worry of a partial blockage.

It just seems to me that the system can't get rid of enough heat to be effective, thats why I was thinking the larger condenser would be a good thing. For those of you that are about to ask if I checked the fan clutch, the answer is yes, not only have I checked it I replaced it just to make sure, but it made no difference.

So now I am looking for ideas on how to seriously upgrade the system because I am tired of no A/C and 105+ degree days!


Please help before I melt!!!!

 

Did it leave the factory with R12 or R134a?
Did it ever work better, as far as you know?
Does it just wheeze out at idle/low speed?
What are the system pressures? Under what conditions?
Was the condenser replaced at some point?

Start by answering those questions.

 

It was converted to 134A, the condenser was flushed by the first shop and replaced by the second shop.

When I bought the truck the compressor was shot.
Cruising down the road @ 65 mph which is about 2000 rpm, the coldest I can get it or anyone for the matter is 56 degrees. Stopped in traffic or parked and it blows somewhere around 65 degrees.

Parked running @ 1800 rpm, ambient temperature of 101 degrees the high side is 280 psi. I don't remember what the low side was.

 

That High side pressure looks ok. The condenser should be ok if it was new. Fan Clutch is new, but that won't matter cruising at 60. ........?

More questions:
Was the orifice tube replaced when it was repaired? (probably was, but I have to ask. Can't just assume).
Are the lines to the evaporator really cold, or just cool? I know it's subjective, but they should feel very cold with the larger tube maybe slightly cooler.
Is the large suction line cool back to the compressor?
Is the blend door in the MVAC box working properly? Has it been checked?

 

The orifice tube was replaced with a red one. That's something I wanted to ask about, are the adjustable orifice tubes that are for hotter climates such as Texas, a good investment? or just more hype.

The lines going to the evaporator are cool but not cold and the drier really doesn't sweat that much.

The suction line really isn't cold at all.


As for the blend door, I don't think it has been checked, I know I haven't checked it.

 

Those variable orifice tubes "can" work in some cases, but they are very prone to failure. They're about 1 or 2 steps above hype. Not worth the problems they can cause.

Has the radiator ever been cleaned externally? On diesel trucks they tend to get an oily film that attracts and holds dirt deep inside the fins.
My thought is that the radiator airflow is restricted somewhat. This is causing the High side pressure to reach a "normal" level while still the system is undercharged. Adding the proper amount of refrigerant would take the High side too high.
If the tech charged by pressure and the radiator is restricted, the "normal" High side reading is masking an undercharged condition. There is also not enough airflow to remove heat from the condenser. It's not real common, but I've seen it enough times that it's a real possibility in this case.

Pull the fan clutch and shroud off. Loosen the radiator, pull it back and spray both sides liberally with detergent (Simple Green or similar, full strength). Let it soak for 10 minutes, rewetting as needed. Then blast in both directions with water to rinse. Repeat.
Recheck the AC operation, preferably while recording the system pressures.

I see in your sig that you have an aftermarket trans cooler. These can also cause AC problems as the cooler adds more heat in front of the condenser that is then pulled into it by the already compromised airflow. It's worse on converted R12 systems. Bypassing the cooler while diagnosing the AC would make the job a lot easier.
How big is the cooler, by the way.

 

highside pressure here in tx on my daily driver I tend to keep it under 300 psi when its 100* outside. Low side on your system should be around 20 psi if I remember right on orfice tube and 10 - 15 psi low side on a expansion valve. mine is expansion valve but converted to R134a and runs around 30 psi low side but puts out cold air though.

Thing is with R134a mechanical fans dont really pull enough air you really should have an electric fan to blow enough air over it to cool the refrigerant down.

I am going to make a post asking a question myself bout a concern I have bout running mechanical with a electrical supplmental fan so if you are thinking about going that route you can check the thread though.

 

Good points Rusty, especially on an older vehicle such as your 82 Truck.
The 93 in question has a somewhat more efficient condenser. They "usually" don't need an auxiliary fan, but with +100* ambient it's a real possibility once everything else is known to be up to par.

 

lsrx101, the aux trans cooler is about 9'' by 6'', so its not really huge.

I will take a look at the radiator when I get a little spare time.

Yesterday while in traffic the compressor decided it had had enough and it locked up. The compressor got so hot the paint was peeling off yikes!

What brand compressor do you recommend? I have been using murray but the seals seem to go bad very quickly.

Assuming I get everything put back together and fix what ever the problem is,what would be the ideal system pressures while it's 100 or so out?

Also, should the system be charged while its idling or while revved up to 2000 rpm or something?
I have asked a couple of ac techs this and I get a different answer each time.

Since I have to replace the compressor, is there anything else I should look at doing?


Rusty, thanks for the info, I will be watching your post.

 

I would go with york. My 78 mercury still has one on it from the factory and it appears to have never been rebuilt (but a york fits sideways on the front of the engine being a newer truck might not be able to run that one). It works great only thing is these old cars that were designed for R12 and I dont mean the 92 and 93 cause those are more efficent I am talking about 1980 and older you should look into a electric fan. it also wouldnt hurt to run one after you convert it over cause R134a requires more air flow than R12 does. Likewise R134a has higher pressures than R12 does so it takes less refrigerant to reach R12 pressure levels.

From the AC tech class I took for my auto tech training they told us to run the engine at 1500 - 2000 rpm preferably 1500 rpm it helps to pull the refrigerant in and it will make sure you have enough for while driving. When you are driving your sucking refrigerant out of the low side quicker so you have a lower low side pressure which means colder air. if you do it on a cycling clutch system with it idling you might not get all the refrigerant in it so when you start driving it will cycle on and off more than at idle. Personally I fill them up idling but I tend to slighly over charge it to take into consideration a good 5 to 10 psi low side drop when going 1500+ rpm.

If your looking at new compressors take a look at the guys at http://www.oldairproducts.com/

They sell retrofit kits to put in more modern ac systems in older vehicles as well as plain air compressors. Their compressors are claimed to only eat up 1/4 - 2 HP compared to the 5+ hp the old ones ate up.

While its 100* outside with the truck running and the ac on your ideal pressure on highside should not exceed 300 - 310 PSI. Your low side for a orifce tube system should be around 25 - 30 PSI low side. Watch your low side and charge it up to what the low side should be which would be round 25 - 30 psi but make sure your high side doesnt go over 300-310. if its not cold enough you can take it up to 30 - 40 PSI and see if that helps long as you dont exceed 300 - 310 PSI. Mine should be around 5 - 10 psi I think or something like that for my expanison valve systm but its running roudn 35 - 40 PSI being slightly over charged just to blow cold air. But the high side is only around 250 PSI even at 100 degrees outside.

 

Ouch! That stinks.


Those Murray/Four Seasons compressors aren't much to write home about. They tend to leak just out of warranty or just plain fail after a couple of years.
The best I can tell you is "anything BUT Murray/Four Seasons".

Check out the Factory Air Brand compressors at Advance Auto Parts if you have one near you. They offer New and Reman, I prefer new but it's your call.
Be sure to remove and check the orifice tube. The amount and type of debris in the screen will dictate what you need to do from here.

At minimum you will need to change the compressor, flush the condenser, change the orifice tube and replace the Accumulator. I would also recommend flushing the entire system and starting from scratch with fresh oil and new orings in all of the hose connections. If there is desiccant in the screen, the whole system will need flushed regardless.

Let me know what you find.

 

I live in Phoenix and have to deal with 100+ degree days.. i added 10" electric pusher fans on both of my trucks..they help big time... was a bit of a challenge to get one to fit on the ranger... and the F250 was a sinch.. plenty of room.. I wired them to come on when the A/C is turned on..(using relays of course..) i don't recommend wiring them directly to the A/C switch
these fans go for about $54.99 over at pepboys..