FJ60 A/C: Low Side pulling a Vacuum? (2 Viewers)

[Gundo]

Okay, I'm well along my way to rehabbing the A/C system in my 1987 FJ60. Pulled a vacuum, waited a good long time, held the vacuum. Proceeded to charge.

And now, here's what's happening

Idle up to about 1,500
Push Blue A/C button, which lights-up
Motor throttles up a bit and Compressor engages
Properly charged with R12
Vent temps unchanged
Hose temps essentially unchanged
Compressor does not de-engage, it just keeps on chugging

What I have noticed though, is that when I turn on A/C, low pressure goes from ambient to a vacuum, like 20 HG, when it should be about 25 to 35 psi

From the research I've done, it's hard to find a definitive answer - in your experience, is that a potentially bad expansion valve? blockage? Haven't tested continuity yet on the low pressure switch

Thanks in advance!

 

[vipergrhd]

Most likely a stuck close expansion valve, you didn't mention what is your high side reading. There is also a chance that your evaporator is clogged or somewhere else in the system. Did you replace any part of the HVAC system?

 

[SteveH]

I agree that it sounds like a clogged expansion valve. I would also check for any physical damage, liked a kinked hard line somewhere.

The expansion valve is 'the thing' (to quote our president) through which the refrigerant evaporates, and it can't pass, then the compressor is deadheading and creating (presumably) very high, high-side pressures. I wouldn't run it too long like this (which I'm sure you have figured out). Having both high and low side gauges might help you monitor both pressures. You can find old R12 setups on CL and at pawn shops, although many have very tired rubber lines and o-rings.

 

[Gundo]

Thanks guys - it's actually pulling 20 HG on low side and is pretty stable at 90 on high side, ambient is 75 degrees F.

I've got the R12 gauges and can pull a vacuum.

Can't recover the R12 though, which I would really like to do if I need to crack this sucker open. I was encouraged that it held a nice steady vacuum prior to charging. Have used the FSM process to fill from empty - which is a bit different and more thorough than the typical youtuber

 

[SteveH]

When you get refrigerant flowing, your high side pressures should go up considerably. You could have a shop remove the R12 and sell it back to you (at a large markup) or just find more R12 and charge it again. There is no great way to do this. You might call around and find a sympathetic A/C or repair shop that isn't run by a jerk who simply wants to work on new stuff.

 

[tmxmotorsports]

When you get refrigerant flowing, your high side pressures should go up considerably. You could have a shop remove the R12 and sell it back to you (at a large markup) or just find more R12 and charge it again. There is no great way to do this. You might call around and find a sympathetic A/C or repair shop that isn't run by a jerk who simply wants to work on new stuff.

Why not just convert over to 134a and be done with it ? Can only get so cold with the thermo coupler.

 

[Gundo]

Found a thread in the 80 forum where someone used compressed air and solvent to clean out the expansion valve via opening the couplings at the firewall, pushing up the low side, and sure enough it worked to dislodge debris that had clogged the expansion valve coming in from the high side. Might be worth a try.

 

[BadReligion]

Most likely the txv. You mentioned rehabbing the system, what was wrong with it originally and what was replaced? Did you put a new dessicant pack in the dryer? How long did you pull vacuum for?

I'd evac the system and change the txv and then either convert to r134 or buy a few more $100 r12 cans on ebay.

 

[vipergrhd]

Sucks you have to redo the whole thing over, but like as suggested get a shop evacuate the system and maybe buy it back from them at a later time when you need to recharge. If you have the time and money just replace the TXV and flush the lines condenser and evaporator if budget allows get a reman compressor just to avoid doing this again all over. Keep us posted.

 

[Gundo]

Okay, so I disconnected high and low at firewall, pushed some air through low side. Some air came out high side, but not much.
The riddle continues.
So, while I’m in here, I’ve decided to switch to R134A. New orings and new dryer also.

Went about removing evaporator (pretty darn easy) and have ordered replacement Denso evaporator to go with my new expansion valve.
I can’t believe just how dirty this thing was. 34 years of sucking dirt sure does clog things up.
Surprised there’s no filter ahead of the evaporator.

Current state of affairs:

my helper (t’was Father’s Day after all)

 

[Gundo]

Update: S U C C E S S ! ! !

And to think I was afraid to tackle this. If you've ever done plumbing, you can do this.

My full list:

Replaced the AC Dryer ($8.45 from MaxAC.com Part # 1411450 Accumulator - Filter Drier

Replaced the Evaporator ($113 Denso OEM part # W0133-1748697 from partsgeek as RockAuto was out of stock)

Replaced all O-Rings ($25 from MaxAC.com Part # MT2582 System O-Ring Kit) (the fancy green ones), including on the compressor)

Replaced the Expansion Valve ($13.55 from MaxAC.com Part # 3411239 Expansion Valve

100 cc of PAG oil ($10, eBay)

1.75 cans of R134A ($30 for 3 cans on eBay)

Put all back together

Pulled a vacuum, which held ($39 Pittsburgh AC Gauges)

Started the motor, idled up, turned on Air Con, fan high

Opened valve on can of freon and let it rip, until about 80 on low side, 180 on high side. Ambient was 85 degrees,

1.75 cans later, and I have air so cold I can make ice. Plenty of ice.

Amazing, and all for just over $200 in parts and unlimited knowledge from IH8MUD!!

 

[Gundo]

Along the lines of working on a 30 year old vehicle, the rubber in one of the A/C hoses sprung a leak. Makes sense as the system had been dry for who knows how long, and running nearly 190 psi on the high side was just a bridge too far apparently.

Trick I learned was to pump system to 140 psi with compressed air, then use soapy water fo the bubble test - easy to find leaks!

Obviously, these hoses are NLA, my fittings are good.
Have shipped all A/C hoses off to www.coldhose.com in Ocala, FL for replacement of rubber using original fittings.
Will keep you posted

Tally so far, new compressor, new evaporator, new exp valve, new hoses (soon), new receiver/drier, new o-rings, and R134A conversion. That's all the soft bits replaced. Only thing left is hard line and A/C radiator up front - which I've tested and seem solid.

And for the "while I'm in there" portion, I've got a new Optima battery, new stainless steel tray and new batter cables on order. Figured that since it's all apart, my battery is old, my battery tray was rubber coated rust powder and the cables are frayed originals, it was time.