OK...today is pretty hot, so I stuck the gauges on it. At idle ( 600 RPM ) it is 50 PSI low side and 250 PSI hi side. Air outlet temp is 61º ambient temp outside is 94º. That is with inside temp normalized after a little driving and then idling for about 5 minutes, inside temp was 79º in the middle of the passenger seat.

At 1500 RPM, hi side pressure goes to 320-330, low side to 25, no cycling and about 50º duct temp. With the blower on low speed, it will cycle. I was adjusted too low ( cycled at about 20PSI ) so I adjusted it to around 25.

I know this is acceptable performance, but I just want to move the temps down about 5-10 degrees.

I think I am going to try a ford orificethe GM is .060" and ford is .049" so I think I will get a better/lower idle temp/pressure.

What I found with the VOV is that it has clearances that give about the same low flow restriction as the ford orifice and the spring is so tense that hardly any deflection happens, so it may as well be non-adjustable. I am going to keep trying to find the right spring to give me about 35-40 PSI idle and maintain 25-30 PSI at rpm under these same weather conditions. So far I cant find any spring that will fit physically.

The question is still out...who has a TXV conversion?

Seems like that would be the ultimate low side regulator.

 

SNIP How to you take the pressure reading to make sure you lower it to 22.5? Someone posted a while back that there was a way to lower the pressure by turning a screw, but then another person posted that the 86 does not have this adjustment feature.

Now that I know my car DOES have this feature I need to do that to mine.

Jake


[Modified by JAKE, 4:06 PM 8/25/2001]

 

Was this test done with the stock orifice? Your low side reading at idle seems high, that is one reason why you are not getting good cooling at idle. Your high-side idle reading is also a bit high at idle. Was this system evacutated before charging? For how long?

At 1500 RPM you said the pressure dropped to 25 psi and you only got 50 degrees at the vent? It should be colder than that if you have a good freon & oil charge. I am guessing that you checked the heat exchanger door for proper operation. I suspect one of the following:

* Air & moisture in the system
* Freon or oil overcharge
* Condensor not operating efficiently

 

rbartick-Thanks for all the info. Is there a site where we can get hi and lo 134a pressures for different vehicles? Some of the reto fits I do leak through the non barrier hoses. Not enough for me to replace a $100 hose, I just have to put in half a can a couple times each summer. However, I don't know how much to put in and would like to use hi and lo pressures to give me a better idea of how much juice is in the system.
Thanks again dude.

 

You may have a good point...
I did not have it vacuated very long last time I changed orifices.
I did put in the Ford Orifice and low side pressure seems much better at idle ( 45 ) and idle temp stays below 60 degrees. I guess I can live with that for a while. Heck, the hottest days are probably gonna be over anytime anyways.

 

You need to pull at least 28" of vacuum for at least 1 hour, longer would be better. You want to get the moisture out of the system. Moisture in the system is probably hurting the system's efficiency. I have also read that moisture will react with the oil and create an acidic residue that can cause compressor failure.

 

TPFKATK,

You cannot charge by pressure. Your pressure will vary depending on ambient temp, blower speed, windows open/closed, and much more. You must charge by volume. It is very difficult to top off a leaking system and know how much freon to add. In addition, if your car is leaking refridgerant it is also leaking oil. If you just top off with freon you will eventually run low on oi, which can damage the compressor.

If you really want to just top off a system you can use the hand-feel method. You basically hand feel the temperature of the evap inlet (right after the orifice) and then feel the accumulator can. If you have enough freon then both should be the same temperature. You should see the metal lines sweating from the evap outlet all the way to the compressor suction line. Idle pressure with the blower on max should be somewhere around 25 psi - 40 psi depending on the outside temp.

 

Thanks again man. I should have been a little more specific. I would not do my vette like I described, I would pop for the hose(s) if needed, and would stay with R12. Mainly I was refering to my beater F250 460cid, 218k on the clock. Uses almost as much motor oil as gas and that's a lot! It's just not worth investing any money not absoutely necessary. So I just put a little 134a in if it's not cold enough. By the way I am EXTREMELY happy with this conversion. Thanks for the tip.
Harold
PS what is your opinion of the air driven vac pump? It is what I use and seems to pull down quite well.....

 

R134a is a mix of 2 different refrigerants. When you charge a system with it you do it as a liquid. This is to keep the mix equal. If you have a leak then your mix can be off since the "mix" will leak at different rates. Also it is very important that the refrigerant boils off inside the evap. This is how the heat is absorbed. As cheap as R134a is, I would remove it, evacuate the system and weigh in the proper charge. I believe the charge is 80% of the R12 rating. Also check the condenser and make sure it is not dirty, or blocked. Good luck

 

Is it just me or are the A/C systems the most overly complex POS in cars?

Why can't they come up with an electric more self contained replacement unit? Instead of spreading the damned thing as a big pain in the foot all over the engine bay and being pulley driven?

Just seems like it would be better then this current overly complex crap ;P