Putting on a new compressor today......
Burning Brakes
Joined: Sep 2001
Posts: 1,166
Likes: 0
From: Tulsa Ok
Re: Putting on a new compressor today...... (Alwyn678)
Don't want to get you started on the while I'm at it thing, but if your opening the system you might as well change out the drier/accumulater, flush everything and switch to 134a, or did you already do that?
Thread Starter
Team Owner
Joined: Jun 2001
Posts: 43,136
Likes: 155
From: Thomson Georgia
Re: Putting on a new compressor today...... (FeedVaal)
Don't want to get you started on the while I'm at it thing, but if your opening the system you might as well change out the drier/accumulater, flush everything and switch to 134a, or did you already do that?
Burning Brakes
Joined: Sep 2001
Posts: 1,166
Likes: 0
From: Tulsa Ok
Re: Putting on a new compressor today...... (Alwyn678)
I took off the drier and the line to the orifice tube that has the low pressure cutoff switch. I pulled the orifice tube and poured about a quart of mineral spirits down that hole then another quart into the hose going to the condenser. Then applied shop air while burping the other end of the line (put thumb on take it off-repeat). Let it sit overnight to dry completely then stuck it back together with new O-rings and pulled vacuum. After a little reading, I found it is way easy to overcharge with 134a and you won't get great cooling with the low pressure switch cutting out too early, so I found an adjustable pressure switch for a later model chevy but had to manufacture a fitting to adapt it to the original port. I managed to get it to cut out @19psi after many attempts.
I used two cans of refregerant and one of those little Maxi-cool additives which brought the low side up to 38 and high side was 225 on a 95* day.
Vent temps are 50~60. I also sprung for one of those VOV orifice tubes but can't say it's worth it with these vent temps. I've read that a Ford blue orifice tube is good for better cooling with 134a and will try that next time I open the system.
I used two cans of refregerant and one of those little Maxi-cool additives which brought the low side up to 38 and high side was 225 on a 95* day.
Vent temps are 50~60. I also sprung for one of those VOV orifice tubes but can't say it's worth it with these vent temps. I've read that a Ford blue orifice tube is good for better cooling with 134a and will try that next time I open the system.
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Putting on a new compressor today...... (Alwyn678)
The low side pressure should be around 26-28 with the engine running 2K. 38 is too high tocool very well. You vent temp should be 42-46degF. :cool:
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Putting on a new compressor today...... (FeedVaal)
I think you will find the pressure will be somewhat higher at idle and then go down as the engine is revved. If pressure is high It won't cool well at low speeds and if the pressure is low, the system will freeze (as in ICE) at hiway speeds and airflow through the evaporator will get blocked. You need to find that "sweet spot" where it works the best. With R134a it is a trial and error thing but when you get it right, it works great. Note the pressure and rpm so you can duplicate it when you need service.
[Modified by silvervetteman, 6:59 PM 7/18/2002]
[Modified by silvervetteman, 6:59 PM 7/18/2002]
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: Putting on a new compressor today...... (silvervetteman)
What I had been advised at the AC forum to charge by high side pressure, high side pressure should be 2.2 to 2.5 times the ambient temp. It translated to about 26# low side 230# high side at idle the day I charged it. I get 42-45 degree outlet air, the pressure does drop as RPM goes up. This is with R134 new drier/accumulator and variable orifice valve(VOV). Good Luck
Scott
[Modified by Scott78, 6:27 PM 7/18/2002]
Scott
[Modified by Scott78, 6:27 PM 7/18/2002]
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Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Putting on a new compressor today...... (FeedVaal)
Cooling is a direct relationship of low side pressure. There is no exactly correct pressure for all conditions. Temperature and humidity and condition of the components are variables that are always changing. Everything is a compromise. The key is find what works best for you. I realize that newer systems are regulated better and are more efficient but working with the older systems can give you very good results. My stock 69 system keeps me nice and cool when it's 95deg and humid.
