ac recharging

[gr8fl4porsche]

Can anyone point me to some specific instructions on adding r12 to an 87. I have not charged an ac system in 15 years and would like step by step instructions. Everything I have found has been geared towards 134a or pre87 cars.

Everyone have a nice week.

[R22tech]

1) get manifold refrigerant gauges w/r12 scale
2) get r12 refrigerant: the real stuff
3) remove sight glass cover behind drivers front wheel
4) install guages on valves of compressor correctly, a blue cap should be on suction/low side and a red cap on discharge/high side.
5)route charging hoses away from moving pulleys and out of the engine bay over the right rear fender(protect fender w/ something as to NOT scrtach).
6)close engine lid, obviously not completely
7) turn car on and have helper rev to about 1750 rpm and hold
8) turn a/c on to coldest setting and fastest blower speed
9) install r12 by opening the low side manifold, watch the high side pressure until it reads 150 psig.
10) close off low side manifold- you should be in the vicinity of about 35 psig.
11) fine tune the charge by looking at the r12 scale on the guages: low side is ideally about 40 degrees and high side about the sum of the outdoor temp. + 35 degrees.
12) check sight glass to verify that ther is no bubbling going on and the floating ball is at the top.
13) center vent outlet temps should be about 38-40 degrees.
14) turn off a/c and car and remove hoses. replace valve caps.
15) you are done

-------------or----------

If the system is completley empty and you have already pulled a vacuum to clean out any contaminates and verify no leaks, you can always just use a weight scale and weigh in the number of ounces your system calls for: the sticker should be on the black plastic housing in the engine compartment blower.
This method will not tell you the health of the sytem though, so do it using the 1st method if you can.

note: if the system has problems, the pressures will NOT behave as I described. Do not just ignore this, report back and let us know what you got so we can advise.

[gr8fl4porsche]

Thanks for the reply R22tech!.

I do not have any caps on my compressor and its difficult to trace the lines as they both go forward into the fender well and out of sight.

From my reading I assume that the upper port is the high pressure side and the lower port the low side. The lower ports refrigerant line is larger than the upper.

Seem correct?

[R22tech]

Yup. Plus, you can just check your readings on the guage- put some freon in, 1 pound, and then proceed to start car and run a/c as instructed above. Your guages will tell you if you have them on the wrong ports, i.e. if the blue, suction line guage is reading 100psig and the red is reading 15 psig-you got 'em reversed. This is important not only from a reading standpoint, but you always want to charge it through the suction line ONLY. ( it's o.k. to put a little in through the discharge(high side) as long as the system is off.)

[schulr]

R22Tech, have a 134 conversion that I have rechargeda few times but it keeps leaking down. Not sure where as I have seen no indication of leakage. When fully charged to 40 or so, it cools very good. Any ideas as to where it is leaking?

Bob

[R22tech]

Man, it could be anywhere! There are so many places for it to leak I couldn't even begin to speculate. You just gotta check every fitting you can find and then ask again- that way we can narrow down the search.

[gr8fl4porsche]

I put a can of R12 in this morning.
Can emptied very slowly.
High side hit 200 psi.
Low side about 25psi.
Sight glass had ball on bottom with tiny bubbles evident around it.
Freon went in with car at about 1800 rpm and tail down.


I just checked it again with the car running and the tail up.
I forgot to check the readings with the tail down.
300 psi on the high
32psi on the low (both with tail up)
ac reads about 70 degrees - temp is about 86 outside.
ball still on bottom of glass.
Front condensor fan is running.

Please advise

[Decolliber]

Why is it necessary to close the engine lid (step #6)? I noticed that the guy who recharged my a/c a few weeks ago left the lid open.

[88911coupe]

The reason you keep the engine lid closed is to draw cooler air OVER the condensor (or evaporator, I always get the names assbackwards). Anyway, it's the radiator looking thing in the lid.
Also, how good are the black light leak detectors. I have added one can of R12 and would like to check for leaks before I add the second one.
Later

If it's in the decklid, it's should be the condenser. The evaporator ought to be in the cabin somewhere. Correct me if I'm wrong!

Does it matter if you hold the freon bottle right side up or upside down? I'm studying vapour cycle air conditionind systems for an Airframes exam on Monday. I seem to remember the textbook mentioning that held upright, the freon can will emit freon vapour, and help inverted, it will emit liquid freon.

The compressor inlet is drawing in low pressure vapour from the evaporator, right?

By the way, if the system is empty, do you need to consider refilling or checking any oil as well as freon?

If this has served only to aggravate and confuse everyone, please disregard it.

[R22tech]

The pressures are out of line, you have a restriction somewhere. Could be a clogged receiver drier, malfunctioning expansion valve, or you might have moisture in the system. I would evacuate/recover the refrigerant, replace the receiver drier, put a vacuum pump on there for a full 24hrs, then recharge system and see how that works out. It's not gonna work with those pressures as I'm sure you have already figured out. The engine lid MUST BE DOWN when a/c sytem is on! You could blow a condensor or high side line due to the increased pressure created by lack of a fan blowing: it's like sticking a screwdriver in your home's a/c unit to stop the fan from turning-things get hot real quick! BTW: you can't charge it correctly with the lid up unless it's below 65 degrees outside.

I don't use the black light leak detectors, but they are good. I think you have to add dye to the system though. I don't like that idea even if they say it won't affect the system.


You said you are adding "cans" of r12? Are they the real deal? I ask because another pelican brought cans of stuff labeled r12 for me to install, and it sure wasn't r12!!!! Bought it off the internet

All freon= gas vapor with can/jug up, liquid upside down. Don't charge it as a liquid-the compressor doesn't like that....

Right, I didn't mean to suggest that someone would want to pour liquid freon into the compressor. Since liquids are uncompressible, the compressor would have a hard time compressing!

[88911coupe]

Resurrecting an old thread to ask a question or get clarification since I'm recharging the ac on my rebuilt 3.2. I don't know which coolant I'm going with but my issue is generic so I don't think it matters.
I've run the vacuum pump through the guages with both the high and low side open and there don't appear to be any leaks, since I closed off the vacuum pump line and detected no change in pressure after several hours. Now, when I add the refrigerant, i.e. 134 or whatever, I will connect the can to the service hose (center hose) and then open the LOW side connection which will suck in the refrigerant due to the vacuum state. Here is my question...assuming I need to add, say for example, 3 1/2 cans of whatever coolant, do I add as many as I can just using the vacuum state of the system and THEN turn the car on and run at 1800 rpms to pull in the rest? OR, do I need to run the car at 1800 rpms for all the cans of refrig? I also assume I can just shut off access to the center hose and check the pressures to make sure things are looking good. I seem to recall getting 30 and 250 on the low/high side respectively a couple of years ago when I was just checking the system pressures out. I"m leaning towards something like Freeze 12, if that matters.

[DRACO A5OG]

Thanks so much R22Tech!

Your reply is very timely.

Jim

Question, if my high side is too high. I assume I would disconnect my center fill hose, close off my low side and open the high side until I get the proper reading?

No worries, I have ES12a, not violating any laws. R12 have long since been properly evacuated from my system.