Holy head pressure!!!!!

[FLYONWALL9]

Ok so its gotten WAY too hot to deal with no AC. I decided to go into the AC shop and see what we could do. Found out one of my schrader valves was leaking. Last year when I charged the system we added the dye so later I could check for leaks. Today we found NOTHING, knowing it had to go some place I removed the cap on the valve closest to the oil fill cap (not sure if that is high or low side). Once we replaced that valve we again pulled a vac for a good hour or so and it held fine.

So, we put in about 2.1lbs with the engine rpm at 2k engine bonnet closed the thing was reading CRAZY pressures. We got a reading of 32psi on the low side BUT 325 on the high side. Now its 98deg outside and prolly close to 90 in the shop we were in.

I've decided to add a fan to the rear in the engine compartment and am seriously thinking of upgrading the fan at the front bumper.

Surely these high side numbers are far too high???

[GH85Carrera]

Yea, the compressor seal will not handle that for long.

I did have a fan blowing at the engine compartment when I did mine.

[dshepp806]

You running 134a?

Doyle

[FLYONWALL9]

Originally Posted by dshepp806

You running 134a?

Doyle

Yes sir....

Any idea's on what pressures I should be seeing? The amount I used
correct? It seemed to be about what I have read in other threads.

[lupin..the..3rd]

you need more / larger condensers. the puny little r12 condensers are not enough for r134 to work correctly. all else being equal, r134 requires lots more condenser surface area than does r12. the original a/c system on the pre-964 cars sucked even when it was new. changing to a lower performance refrigerant like r134 only makes matters worse.

you also need to replace all 30+ feet of a/c hoses with newer barrier type hoses.... unless you like recharging your r134 every 4 months.

[wwest]

Originally Posted by FLYONWALL9

Ok so its gotten WAY too hot to deal with no AC. I decided to go into the AC shop and see what we could do. Found out one of my schrader valves was leaking. Last year when I charged the system we added the dye so later I could check for leaks. Today we found NOTHING, knowing it had to go some place I removed the cap on the valve closest to the oil fill cap (not sure if that is high or low side). Once we replaced that valve we again pulled a vac for a good hour or so and it held fine.

So, we put in about 2.1lbs with the engine rpm at 2k engine bonnet closed the thing was reading CRAZY pressures. We got a reading of 32psi on the low side BUT 325 on the high side. Now its 98deg outside and prolly close to 90 in the shop we were in.

I've decided to add a fan to the rear in the engine compartment and am seriously thinking of upgrading the fan at the front bumper.

Surely these high side numbers are far too high???

Surely...too high???

No, apparently not.

Binary Switch w/ R-134a Discharge Port 7/16" - A/C Pressure Switch

[Por_sha911]

Did you have the engine running with deck lid lowered when you were charging the system? You will get very high pressure if not.

[Hugh R]

I got rid of my deck lid condenser and got better results with a fan/condenser in the L/R wheel well. The decklid one gets heat soaked (when you are idling/stuck in traffic, and can't get rid of that heat very well. I also slot cut the trunk above the front condenser and put a bunch of double stacked high speed computer box fans in. The original fan only blows air across a very small surface of the condenser. The bad thing about that is you're pulling outside air into the trunk, where as the squirrel cages original fan doesn't do that.

[Neel]

Originally Posted by FLYONWALL9

Ok so its gotten WAY too hot to deal with no AC. I decided to go into the AC shop and see what we could do. Found out one of my schrader valves was leaking. Last year when I charged the system we added the dye so later I could check for leaks. Today we found NOTHING, knowing it had to go some place I removed the cap on the valve closest to the oil fill cap (not sure if that is high or low side). Once we replaced that valve we again pulled a vac for a good hour or so and it held fine.

So, we put in about 2.1lbs with the engine rpm at 2k engine bonnet closed the thing was reading CRAZY pressures. We got a reading of 32psi on the low side BUT 325 on the high side. Now its 98deg outside and prolly close to 90 in the shop we were in.

I've decided to add a fan to the rear in the engine compartment and am seriously thinking of upgrading the fan at the front bumper.

Surely these high side numbers are far too high???

33oz in a retrofitted to R134a a/c unit is a bit too much charge, if your system is otherwise stock.. A 10 to 1 high/low pound ratio was considered ideal in R-12 days.. It's a different world out there now!!! The first thing I would do is install the high/low switch referenced above by wwest.. When you recharge your system, do so in small increments and closely monitor your high side pressure.. Once you get what you have working properly, you can determine what you want to do to increase the efficiency of your system.. In other words: "Cold costs money, how cold do you what to be?"
I feel your pain (heat)living in the South.. Good luck!!

[Neel]

BTW, if you still have non barrier hose, dye will not show a leak through the hose..

[FLYONWALL9]

Thanks EVERYONE for your replies! Truly valuable information, I am very new to this and learning or trying to that is. I will get the high/low switch, that seems to be a pretty inexpensive upgrade. I honestly do not understand what it does or will do?

I have two slim line fans that would fit on the rear deck lid. However, this is how I'm looking at it. That front condenser has about as much fan coverage as a SubWay Club. So, my plan is to cut two circles out of the rock guard just large enough as needed. I did some quick measurements and it looks like the fans will only be below that rock guard about 3/4 of an inch. I'll attach the fans to the inside of the rock guard and samwich (I must be hungry, two food references) the fans between the two. I don't think that will cause any ill issues. It cant hurt to try, even if I improve flow 20-30% conservative that should be a good improvement. I haven't found many posts where members did a mod of this sort. Could mean its not worth the effort, too much of a PIA, or I just searched wrong.

NEEL,
Can you help me understand what should be the proper amount of 134 I should expect to use in OZ? I would rather have less than have this high of head pressure. I cannot afford to buy a new compressor, though it would likely be better than what I am using now. After I install my fans I'm going to head back up tomorrow to put it back on the gauges to see what it reads and also pull out your recommended amount. THANKS....

[FLYONWALL9]

Originally Posted by Hugh R

I got rid of my deck lid condenser and got better results with a fan/condenser in the L/R wheel well. The decklid one gets heat soaked (when you are idling/stuck in traffic, and can't get rid of that heat very well. I also slot cut the trunk above the front condenser and put a bunch of double stacked high speed computer box fans in. The original fan only blows air across a very small surface of the condenser. The bad thing about that is you're pulling outside air into the trunk, where as the squirrel cages original fan doesn't do that.

I was wondering if I made a shroud that the condenser sat in. Picture a box with an opening for the fan to screw to. On the side facing the outside of the car I would close it off that side and have the opening on the opposite sides so that it would draw air in the far side and across the condenser. I would think doing this would better equalize the flow over it rather than having one side cooler than the other. Or do you think this is a wasted effort?

It really amazes me when you look at how simple and small system is in something like a DelSol is and how well it works. Just baffles me why we cant come up with something like that. Heck those condensers in those small cars are about 1/3 the size of our if you combine all our bits........

[FLYONWALL9]

Originally Posted by Por_sha911

Did you have the engine running with deck lid lowered when you were charging the system? You will get very high pressure if not.

Yes, the lid was closed (only cracked enough for the lines for the freon pump). Engine RPM was 2000 the entire time we were adding freon

[FLYONWALL9]

I'm not gonna waste a bunch of ya'll time simply to say my mod works like a champ!
Sure the fans hang lower than the bar in the front but still able to ease up to a parking
stop without issues. Conditions are damn near the same as the day I first worked on it so almost 100deg

Some stats
We took the freon charge down to 2lbs
32psi low side at idle
275psi high side at 2000rpm.

I think those are pretty good numbers. I'm not going to say its throwing ice at me but I was
comfortable on my drive home from the shop. I still think I may add one or perhaps 2 motorcycle
size fans in the rear. That should help greatly. I feel anyway.

THANKS EVERYONE FOR YOUR REPLIES!!!! you guys are the best.

[Neel]

Glad everything's working the way you want!! I sent you a pm the other day, I hope you got it!!

[Flat Six]

Originally Posted by FLYONWALL9

I will get the high/low switch, that seems to be a pretty inexpensive upgrade. I honestly do not understand what it does or will do?

I assume you're running a compressor that's been converted to R134a service port fittings?

Switch goes on high-side port; some models plumb in-line between high-side port and first condenser (IIRC Griffith offers a replacement high-side to condenser hose that has the switch plumbed in-line).

Or you can use one that attaches to the high-side service port instead.

Note that the add-on swithces from ACKits and Nostalgic Air screw onto the 7/16" (R-12) service port and replace it with an R134a service port instead.

In either case, the switch is wired in series with the compressor clutch so that the clutch is not energized (engaged) when:

-- AC switch is off (normal with or without cutoff switch)
-- high-side pressure exceeds upper limits
-- high-side pressure falls below lower limits

HTH

Dale

[FLYONWALL9]

Originally Posted by Neel

Glad everything's working the way you want!! I sent you a pm the other day, I hope you got it!!

NEEL,
I did thanks much, your info was one of my major sources for the proper
amount of freon that I used.

Sure, I am SURE it can be far better than it is now but for 20 bucks spent
I think I am doing pretty good at this point in time.

MAYBE, after I do all my int. restoration I may dump some real cash into
the AC to make it really worthy of living in the deep south. I can live without
a heater but I'm getting too old to live without AC comfort.

THANKS FOR YOUR HELP NEEL!

[FLYONWALL9]

Originally Posted by Flat Six

I assume you're running a compressor that's been converted to R134a service port fittings?

Switch goes on high-side port; some models plumb in-line between high-side port and first condenser (IIRC Griffith offers a replacement high-side to condenser hose that has the switch plumbed in-line).

Or you can use one that attaches to the high-side service port instead.

Note that the add-on swithces from ACKits and Nostalgic Air screw onto the 7/16" (R-12) service port and replace it with an R134a service port instead.

In either case, the switch is wired in series with the compressor clutch so that the clutch is not energized (engaged) when:

-- AC switch is off (normal with or without cutoff switch)
-- high-side pressure exceeds upper limits
-- high-side pressure falls below lower limits

HTH

Dale

Dale,
Thaks for that! Do you think I should still go ahead and get that
switch with the numbers I posted? Would it help? I'm guessing
it would act more like a safety type deal.
PLEASE PARDON my AC IGNORANCE !!!!!!!!!!!!!!!!!!!!!!! I did read
a little about them but knowing the system was over charged and
I was going to add the front condenser fan. I really wanted a good
usable baseline to work off of. Now that I know I can run the system
without blowing something up.......

I know the switch is only a few bucks and I get what your saying
where and how its installed. Worth the effort? Because I would have
to bug my buddy to vac my system down again. Soon, I'm going to have
to buy him a bottle of his fav booze.

[Flat Six]

Well, I think it's required w/a R134a conversion (legalities etc.), as is proper labeling so an AC tech, next owner, etc. will know.

Don't forget the hi/lo switch also protects against compressor running when pressure is too low -- typically (though not always) happens when you've leaked a sufficient amount of refrigerant. Running compressor w/too little refrigerant is not nearly as big an issue as running the compressor with too little oil. Lose the refrigerant and you lose the oil, too. Compressor screeches, seizes, needs replacement.

At any rate, I think it's cheap insurance. And if you have a buddy who's an AC tech, buying him a bottle of his favorite booze is a wise investment, too IMHO.

HTH

Dale

[Neel]

Originally Posted by Flat Six

Well, I think it's required w/a R134a conversion (legalities etc.), as is proper labeling so an AC tech, next owner, etc. will know.

Don't forget the hi/lo switch also protects against compressor running when pressure is too low -- typically (though not always) happens when you've leaked a sufficient amount of refrigerant. Running compressor w/too little refrigerant is not nearly as big an issue as running the compressor with too little oil. Lose the refrigerant and you lose the oil, too. Compressor screeches, seizes, needs replacement.

At any rate, I think it's cheap insurance. And if you have a buddy who's an AC tech, buying him a bottle of his favorite booze is a wise investment, too IMHO.

HTH

Dale

A big +1..