I would suspect that the reason it doesn't cool as well has nothing to do with the type of freon or compressor.  The issue is the condenser is too small.  R134a needs more surface area because it carries more heat with it.  There are companies out their like Classic Auto Air that sell a 6 pass condenser that should solve that problem.  Another common issue is not recalibrating the compressor cycling switch.  R12 and R134a need to cycle at different pressures.  You want it to cycle at 21-22 psi.  There should be a screw in the top of the switch that allows adjustment.  I think turn it clockwise to decrease the pressure, and probably 1/4 turn or so will do it. 

I'd be quite concerned with why the compressor is continually dying.  What oil is in the system?  R12 (mineral oil) and R134a (PAG) oils are incompatible.  There is a conversion oil that solves the incompatibility issue.  If the system is not new or fully flushed you MUST use that conversion oil.  The old hoses, etc. all soak up and hide that old mineral oil.  The hoses, honestly, its best to change them if they're old so you know you have barrier hose that won't leak R134a right through the hose. 

Charge wise you should use about 85-90% of the charge you'd use for R12. 

The Sanden is a good compressor, and like I said, if you're having issues with it I suspect something else in the system is amiss.  Be really sure you get all the moisture out of the system before charging.  I like to vac them down and let them sit overnight with vac on them. 

Who made the compressor?

When the AC quit on our Mazda, I bought house brand from O’rielly’s for less than $200. The first one didn’t make it all the way charged and it was making excess noise. O’rielly’s wrote it off as defective and got the second one. #2 lasted about 6 weeks and failed. That one was returned for a full refund.

The warranty was great, but I’m out my time and $50 of refrigerant per swap.

Bought a Motorcraft brand from Rockauto. It’s been on ther 2-3 years.

Another option is to just rebuild it yourself.  Typically you can do it for about $35 worth of parts if you already have a clutch puller.  If not you can get a free loaner from Pep Boys, etc.  I bought a full set from Amazon a while back that cost like $50 to avoid having to run to Pep Boys if  need the puller.

The Sanden is a swash plate style compressor.  I've never had a Sanden apart, but I've done Nippondenso compressors that are also a swash plate style and are on just about everything now.  The design is inherently a good one, and they only suck up a couple HP in operation compared to the old piston style that could gobble down 20HP and go back for seconds.  Really not much going on internally either.  There's a handful of seals to replace.  The bearings, thrust washers, etc. should never wear out and just get reused.  The only real trick is being careful not to touch the carbon seal with your bare hands.  Getting the pistons back on the swash plate is a little tricky, but you just have to stick everything together with refrigerant oil.  There's a ton of videos and such online that is super helpful. 

Bolted to Floor wrote:

Who made the compressor? .

 
It is a "NEW" brand compressor, model 194510 made in China.

I don't know what makes the pressure so high except a plugged up system or too much freon. The expansion valve is a new unit (10 years ago) for R134a but is not adjustable. But again I don't believe it is a gage issue because cars that are factory made for R134a work normal. The only thing that is not made for R134a is the evaporator and I have a hard time believing that is the culprit.

I just got back from a TKO test drive as I'm messing with the distributor timing. But while I'm doing that I put the thermometer in the vent and it is cooling down to 46º in town and on the freeway. The compressor makes a lot of noise when the RPM gets up to around 3000. The engine didn't heat up and ran perfect power wise. I don't think it is anything else except the compressor laying an egg. The condenser was made for my year car for R134a so I don't think it is that, but I'm no expert. I don't know how to tell by what I'm looking at though It is thicker than the stock unit.

Or buy a used real deal Sanden and rebuild it.  So long as it spins, even if its notchy where each piston moves I'd risk it.  A thorough cleaning, new seals, and a light coat of oil on assembly and I'll bet its butter smooth when you're done and works like a champ. 

BillyC wrote:

I would recommend replacing the compressor with an actual Sanden unit instead of the "Sanden type" Chinese knock off.

 This.
It's funny how we all know Chinacom parts are inferior, but still keep replacing  them with the same part.
You woulda been miles in front specing a Sanden when you did the swap.

Yep, and with that stuff you risk improper machining and/or bad metallurgy.  Then, if the compressor sends shrapnel through the system you're out a condenser, and evaporator, etc., etc., etc.  To say nothing of labor, freon, oil, etc. 

$80 seems kind of over the top to me. I would think somewhere closer to $50 would get you what you need.

Got the AC finished. Who-Raw! I works as good as originally. It got down to 45º at 190#'s on the high and 25#'s on the low side. The OAT was 78 when I charged it. That helps. I took the guts out of the quick disconnect in the liquid line cause I couldn't remember how it went back together and got tired of monkeying with it. Been raining here so I haven't driven it yet. The roads are slick.

Last edited by HudginJ3 (8/12/2018 1:38 PM)