Frankenrex

iTrader: (1)

Agree. I should have added that above.

7dust

iTrader: (14)

Working on an 88 RX7 that had the AC removed under the hood and I pieced together the whole system.

Didn't have an adapter to draw a vacuum on the high side so figured an extra long vacuum on the low side would work.

I put the first can in and all was good. When I went to put the second can in, the compressor blew out its pressure release? on the back. It also started leaking oil along the seams of the compressor where the bolts hold it together.

The compressor never cycled off. But I only got one can in. I'm guessing the free compressor I was given of quality unknown was ready to commit suicide?

I'm going to buy another compressor but was wondering if I did something stupid-er than usual.

7dust

iTrader: (14)

After the compressor finished venting, it seems too still be ummmm compressing.

Air is cooler than ambient but not by much. High side line is super hot.

Low side shows 45 and compressor does not turn off.

RotaryEvolution

iTrader: (30)

sounds like you have an obstruction in the system. i normally add in about 20 ounces for an FC and don't have any issues with the R152 refrigerant.

it does labor the compressor but it shouldn't be overpressurizing like yours did.

R134a is stupid expensive these days... in a few years it will be nearly as expensive as R12 was before it was phased out. i don't get it, while R152 is still about $3 for a 12oz can. if you have a leak in the system it's $50 wasted for a simple test with 134a... screw that. Fry's diflouroethane duster 3 pack 12oz cans, $9 which services 2 cars! even without upgrading the condenser core it still blows colder on average than even the best 134a refrigerants i have come across.

find the obstruction and for the best results pick up a compressor driven vacuum pump for $20 and evacuate the system into a vacuum, add in about 4oz of oil/dye and then recharge the system. most likely you have a plugged up receiver/drier.

skipping the vacuum step results in air in the system and not a full charge and reduced efficiency.

7dust

iTrader: (14)

How does the compressor know when to turn off and why would it happily keep turning if its overcharged (after one can?) ??

I guess I need to find a way to connect to the high side to see what its doing. Maybe the compressor is still good since the system is still holding pressure, it just farted a lot out the back of the compressor.

Are the high side and low side really that isolated? Is it really necessary to draw vacuum on both sides? I charged my RX8 by vacuuming on low side only. It worked fine.

RotaryEvolution

iTrader: (30)

iirc there is no overpressure switch on these cars, they are rather primitive.

if the low side goes over pressure the pop off valve on the compressor will dump excess pressure. you could technically have a faulty pop off valve but it doesn't seem to be a common occurrence.

i only draw the low side into vacuum for about 20 minutes, it should create a vacuum throughout the whole system, i missed the part where you had evacuated it but i still would say you have a faulty compressor/popoff or an obstruction somewhere.

if it's dumping pressure with less than a normal charge then the low side isn't allowing the vapor to pass through the evap core, which usually is caused by a kinked line, plugged up reciever/drier or a blocked up orifice on the evaporator(reverse flush the evap core since it isn't ideal to remove it and flush it).

7dust

iTrader: (14)

I'm pretty sure system has no kinked lines. I replaced everything under hood piece by piece. The only thing I have not (couldn't easily check) checked is the evaporator.

I was asking what triggers the compressor to cycle on and off since the compressor comes on, but will not cycle off.

I replaced drier with a new one.

RotaryEvolution

iTrader: (30)

there is a low pressure switch on the low side line just to the inside of the receiver drier.

7dust

iTrader: (14)

I see the low pressure switch and plugged the most likely wires to it to make it work.

If I unplug them, it turns off - so I guess I got it right.

RotaryEvolution

iTrader: (30)

yes, it just does not open the switch in the case of overpressurization. it saves the compressor in the event that the system has a leak and loses lubrication oil.

jackhild59

iTrader: (7)

I routinely use only the low side for vacuum.

Describe and explain your extra long vacuum procedure. Include details regarding the equipment used and how it was attached etc. Add in the charging sequence.

Sounds like an exam quiz, lol. You obviously have non condensables in the system, most likely air. Somewhere you either sucked in some air or didn't get it all out. This is the number one problem with self-inflicted A/C difficulties.

7dust

iTrader: (14)

^^^ Now that I think about it, there MIGHT have been a couple opportunities for air to get into the system.

I vacuumed the system for 30 minutes. Gauge showed -30 and held it for a couple days while I waited for a friend to return my can tap.

I vacuumed the system for 30 more minutes because I was drinking beer and felt like I should be doing something constructive at the same time.

With the low side closed, I tapped the first can and bled the line. I noticed that the Schrader valve on the R134A fitting on the can tap was venting out. (can tap has R12 and R134A service fittings) I figured it was no big deal since it was venting out, not sucking air in. Next time I'll put a service cap on the other fitting or tighten the other Schrader.

The can didn't fit too well in the can tap. It sprayed me a lot and I eventually jammed it in place. Its been a while since I used it so I forgot it needs a small piece of folded cardboard for a spacer. Might have sucked air in at this time too.

Compressor came on, car sucked in first can, I closed valve, and tapped 2nd can. It flowed for about 5 seconds and safety release in back of compressor popped off. Also looks like seams of compressor in front were leaking?

I cussed, went back inside and finished drinking beer.

Went back outside. System is holding charge now but is barely cool. Low side shows 40 when on, does not cycle off.

I was sure my compressor was / is toast but checked it this morning. System still has refrigerant in it and turns on. Still not cool. Hopefully its not fried.

Going to re-evacuate system, introduce a few Lone Star's into me, and be extra careful not to introduce air into the system.

It HAS to be air since I only got one can in before the system **** itself?

I've used this guide to charge my FD twice and my RX8 once and I thank you for it! Never had this much trouble before.

jackhild59

iTrader: (7)

Well, at least the beer was cold!

Seriously, I would re-vacuum and recharge. The air entrainment is the only way you could have gotten an overpressure.

My best guess is that when you had the system under vacuum, sometime you allowed the vacuum to suck in some air.

Do you have a manifold gauge set? If so, make sure the valves are turned off before you turn off the vacuum pump and undo anything. Then make sure you fully bleed the hoses. A little bit of liquid coolant spraying out is the key to assuring your hose is air free.

I had my fan unplugged once while testing and forgot to turn off my A/C. It vented the safety plug on the dryer-that is a permanent vent. Scared the crap out of me. It went off with a loud bang! Another time the pop off on the compressor vented. I had hooked up 6' hoses and charged while driving at about 35 mph. The pressures both high and low were fantastic at speed. I thought it would be a great way to get an accurate charge. Nope. It was a great way to get the system seriously over charged. When I came to a stop sign, the highside pressures quickly went to 375 then 450psi. The compressor rumbled, then vented. My compressor still works fine and I still have 38-40* air. You should be fine.

Lesson learned.

7dust

iTrader: (14)

Since we are tattling on ourselves about stupid AC mistakes, many years ago I had a slow leaky Schrader valve on the low side of my convertible.

I had a foot long charging hose with a valve on the can tap end.

Simple enough fix I figured - leave the hose attached after charging, just tuck the can away to the side. If the system needed a little top off, open the valve, close it, and get on about my business. That way I wouldn't waste a can

Well this was fine until a very hot summer day and the car was freshly shut off - leaving it to stew in its own juices.

Finally I guess it got so hot under the hood that the can exploded! It put a big dent in the shock tower, a big dent in the hood from the inside, and made a BIG BOOM! I looked at the car right when it happened and it looked like a big chicken exploded. The under hood mat disintegrated and blew out from under the hood by the windshield and the front of the car.

I mean, I still had AC - but the collateral damage to the car taught me a lesson. A service cap works better than leaving a charging hose with a can attached. In case anyone was wondering.

RotaryEvolution

iTrader: (30)

i'm much less careful about air intrusion and have no problems, i still say there is an obstruction somewhere.

7dust

iTrader: (14)

Evacuated.

Tried again.

Blew out overpressure valve on compressor 3/4 through first can.

I hear you saying obstruction obstruction obstruction but geez.

I dont see HOW or WHERE something like that could happen.

Im thinking faulty compressor. Ill have to find way to hook up high side to see whats happening.

7dust

iTrader: (14)

Maybe expansion valve?

Can I get to this and replace it easily enough?

RotaryEvolution

iTrader: (30)

only other way is to see what the pressure is doing before it blows off from the compressor which would require a manifold gauge while adding freon.

i'm not sure about the expansion valves on these cars, i haven't had to service one before so it may be easy to get to or extremely difficult which is why i mentioned backflushing the evap core which the orifice should be on the inlet before the evaporator.

jackhild59

iTrader: (7)

You can 'rent' a manifold gauge set and vacuum pump at Autozone for FREE.

7dust

iTrader: (14)

I have a manifold gauge set and a vacuum pump.

Problem is that I do not have the fitting to connect to the high side. Ive ordered the adapter but it must be on the slow boat from China. :/

pfsantos

iTrader: (1)

Something could be pinched or kinked past the firewall since you said the previous owner left that in.

Re: stupid things done - I once removed a bunch of plugs for some reason I don't remember...then switched the plugs for the horn and low pressure switch by mistake. The A/C didn't work at the time, so the only clue was my horn stopped working. For the horn I ran some wires after resoldering the CPU didn't fix it. It was a few years later when getting the A/C fixed I saw some wires unplugged and saw the plugs for the horn were the same type. LOL!

jackhild59

iTrader: (7)

Brain FArt. I shoulda seen this upfront, sorry I missed it.

I have a pretty good idea what is the problem. The old oem driers had a bag of desiccant (XH-5) that is designed for mineral oil. If you put a synthetic oil in this drier, eventually the bag can rupture. Desiccant beads end up clogging the system at the expansion device. I have seen this happen most often with so called professional conversions done by shops. The usually get paid for the clean up. I had a friend who spent $200 on a conversion and $400 on the clean up on a little nissan pickup. The shop wouldn't take responsibility for the problem. "We've done thousands of these with no problems"

All driers produced since about 1995-6 have the newer XH-7 or XH-9 desiccant bags, so you don't have to worry about this again.

You will need a new drier and a new expansion valve. Give that side of the system-from the drier to the expansion valve- a really good flush with mineral spirits and compressed air. I would remove the evaporator coil and flush that too if it were my car. I would flush/replace the compressor oil if it were mine. If the desiccant got past the valve, it may be in the evaporator, the compressor and the condenser, however this is not too likely. You could put a universal compression fit filter in the return to the compressor if you wanted, but probably not necessary if you flush everything.

-J

turbowash

iTrader: (1)

Found a very interesting study linked below about 152a. I'm about to try 152a with my old refridgerator today and then my rx7 after I put the AC system back together. Ill post my results!

http://docs.lib.purdue.edu/cgi/viewc...3&context=icec

inflatablepets

I thought I would post my two cents. I finally repairs my a/c system on my S5. Replaced compressor, replaced expansion valve, replaced receiver-dryer. I cleaned all the lines, the condenser and the evaporator. I then pulled vacuum down to 500 micron and waited. On scourge note, the oil in the pumps need to be changed regularly to keep them working well. I found no leaks then added small oil charge and then charged with R134A. My a/c blows 34-37 degrees on St Louis's hour and humid summer days. (90-95° 60-80%rh) I get I've cold air, but the blower doesent blow as had as I would like. The temp raised some at stops but it is still nice. I have converted other cars with good results as well. And 134 is cheap. $3.99 a can at Rural King.

RotaryEvolution

iTrader: (30)

if it blows much harder on recirc than it does on outside air then you probably should clean out your wiper ducting. it's probably full of leaves and other debris.