A/C system charging valve location?

[Pinseekers]

Can't seem to find both (high & low) valves.
There is one right on top, above looking glass (obvious location) but where is the other valve???
thanks

[Rob-O]

Bottom of the car. On the compressor...you'll see 'em.

[scottewid]

Seems to depend on what year your car is. From what I understand, the early models have the low side test port(for charging and pressure testing) right on the compressor, and the high side test port (for testing pressure ONLY) on the line running on top of the engine next to the driver's side fender.

On my 1986 951, both the low and high side ports are right on top in plain view on their respective lines running next to the driver's side fender. The low side, where you charge, is the fatter of the two lines and will get cold when the system is running. The high side is the thinner line and gets hot when running. NEVER hook a charge can to the high side because you risk exploding it from the pressure.

[White951]

Hey guys,

I have been interested in trying to find out how to maintain my air conditioning system on my 86 951. I work on the car myself, but don't know anything about the AC. How and where can I find out how to check it out and recharge?


John

[mike944]

White951 -
there's really not alot you can do on your AC yourself, unless you can get your hands on some R12. I believe you can't buy it legaly in the US anymore. I know it hasn't been legaly manufactured in a few years. you can get some black market stuff made overseas, but i've heard it's junk. you might be able to find some at a swap meet, or something, but be prepared to pay for it. other than that, you'll need a gauge set, and charging hoses to do any recharging.

To just check the freon level, find the dryer, which is about a 2.5" dia x 10" metal can in the AC system. there is a glass window (you'll probably have to clean it.) when the AC compressor is running, you should see nothing in the window. If you see any bubbles, that means it's low on freon.

there really isn't any maintenence to do on an AC system. Almost everything involves discharging it, opening it up and recharging it.

Mike

[scottewid]

John, go to www.aircondition.com and www.autofrost.com. They both have great tech articles on how auto a/c works and how to fix it. You should also go to www.epatest.com and take the easy online test for $19.99. This will give you your epa certification 609 that allows you to buy r12 and other refrigerants, also available online from www.refrigerantsales.com.

A/C is really very easy to understand and work on. Once you get your 609 cert and are ready to start working on your a/c it's critical that you get gauges. You simply can't do any meaningful work on a/c without gauges because then you're taking a total shot in the dark and might end up breaking it rather than fixing it. One of the biggest mistakes peoply make is adding refrigerant willy-nilly, thinking that any a/c problem is due to low freon. Most times they end up overcharging which will make your a/c blow warmer, along with other nasty things. You can get new gagues and other a/c parts at www.acsource.com, as well as quality used ones at www.firstcash.com.

If you get really serious about a/c work, then you should also get a vacuum pump and one or two NEW barbeque grill propane tanks. You'll need the tanks to recover refrigerant from any system that has a charge in it before you open it up. You can get the fittings and hoses to hook up the tanks at any hardware store.

[scottewid]

Whoops, try this www.acsource.com the first one had a comma in it.

Also, you can still definitely get R12! True, it hasn't been manufactured since 1995 in the US, but there's plenty still available for sale from existing stocks and refrigerant recylcled from old discarded systems. Auto salvagers and a/c shops that convert cars to 134a are required to drain the old r12 out of systems and send it to recyclers where it gets cleaned up and dried out, repackaged and resold. I buy my r12 from www.refrigerantsales.com and Pep Boys. Pep Boys is more expensive, $45/12oz can versus $40/12oz can online, but sometimes more convenient. When I go to Pep Boys, I just see the manager, show my epa 609 cert card and they get the cans out of a locked cage in the managers office.

[White951]

scottewid,

Thanks for the info. I will definitely check it out. I now r12 is still available, you just pay for it big time. From what I understand from looking online at various sites, I don't even know if the compressor is engaging. I don't think it does because I don't feel anything happen when I turn it on. I have read it may be electrical wiring causing the clutch to not engage or low freon. Off we go into the AC world. Thanks again.

John

[White951]

Scottewid,

I looked at the sites you posted. Is there somewhere in these sites that say "here is what should happen. If it doesn't do this, then this,etc."


John

[Pinseekers]

so how do I charge the system with one valve on top and the other on the underside?
I have an 86 NA. I purchased the kit from Walmart for $35 that converts the system to 134 from r12.
Should I just pay the $208 the pro's want to charge for retro fitting my system?

[scottewid]

Pine, seem my post under "More AC Stuff. Yay". It explains what's involved in a 134a retrofit. I think paying the rather modest $200-$300 for a professional to do it right is worth it. Some folks have been successful with the DIY Kmart kit, but I can't imagine how. Read, the post, you'll understand what I mean.

Also, why do you want to retrofit? If your a/c is working fine now, why not keep it r12. If it's leaking big time, like needign a charge every couple months, then I can understand. 134a will be a lot cheaper to charge up that frequently (assuming you don't fix the leaks) But if it's not leaking, leaking real slowly, or you plan to fix all the leaks, I'd stay with r12.


John, those sites will give you a good overview of a/c and refrigerant theory, kinda a/c 101. When you say you looking for something that will give you steps to follow, do you mean like troubleshooting? If you want troubleshooting advice, go to www.aircondition.com bulletin board. It's the one that says "questions" on the upper right of the home page. Those folks will give you great advice. I may also be able to help if you have a specific question. Scott R and Lawrence C. also are pretty knowledgable about a/c stuff. Between us and others here, we should be able to help.

[Pinseekers]

Thanks Scott. I had already posted the previous message before I read through Andre's post about MORE A/C.
I think in this case I am going to shell out some cash and let the pro's do the job!

[Lawrence Coppari]

Five years ago the AC began leaking on my 21 year old MB Roadster (was only 16 then). I use a substitute regrigerant that is mostly propane. Certainty I was concerned about the refrigerant eating the system but 5 years is 5 years. Well, I let it go for a year because MB parts don't cost as much as P parts. It's been in my 944 for 4 years with no harmful effects. Blow up the car in a wreck - I don't think so. It is distributed and only 60% of the amount of Freon.

[White951]

Scottewid,

My car also is a 1986 951. I looked under the car this weekend to see if the compressor clutch would engage, it did not. I warmed up the car, opened the doors and the hood and turned it on. Like your car there are 2 lines with plastic screw caps running along the top of the drivers fender. What type of gauge do I need to check the pressure and do I hook it up anytime (car running, not running, ac on, ac off??)


John

[justin]

Hey guys Mine is a 83 944 and I really need to know where to charge and check the freon. Is it the lower one by the compressor or the one by the drier on top. i think i charge on the lower one and check it on the upper one? Am I right? help it's hot..........

------------------
Drive it like you stole it........Justin

[scottewid]

White, they're called a/c manifold gauges and you can get them at www.acsource.com. It's basically two gauges with three hoses. One gauge is calibrated only up to about 150psi and the other goes much higher for checking high side pressure.

You can get a cheapo single gauge at Pep Boys, but should get real manifold gauges if you're serious about doing your own a/c work.

You primarily use the gauges to check the low and high side pressures when the system is running. With the compressor engaged, generally, your low side pressure should be between 25- and 40 psi and high should be 150 to 230ish, depending upon outside air temp. If they're lower, you're undercharged and if higher overcharged. There's a whole bunch of other things that can cause screwed up pressures, though, so that's just a rough rule of thumb assuming everything else is working right.

Without the system running, the pressure in your r12 system should be about 60-80 psi, depending upon outside air temp. If lower than that, you're probably way low on charge and this is preventing the compressor from turning on. The cheapo Pep Boys gauge can tell you this (I even hooked a fuel pressure gauge onto the low side schrader before I got my real gauges.)

Justin, I don't really know about the early cars, but from what I hear, the one on the compressor is the low port where you should charge.

[justin]

Thanks Scottewid thats kinda what i thought too.

------------------
Drive it like you stole it........Justin

[White951]

Scott,

Sorry to keep asking???

If the low pressure side is low, how do I know how much r12 to put in. Do I just put some of the can in, and then test it again, or if it is down to a certain pressure then 1 lb or 2 lbs should be good?

John

[Lawrence Coppari]

The low pressure side should be between 20 to 30 psi while the engine is running with the AC blower on high and engine at about 2000 rpms and outside temperature 80 F. A flow through gauge is helpful here. I would charge a little, shut off valve on can to make sure you are getting AC system pressure. I would add refrigerant until gauge attains proper pressure. Or I would add until bubbles disappear in sight glass or until a thermometer in the duct vent of dash reads about 50 F. For substitute refrigerants, you cannot go by bubbles in the sight glass.

Pros evacuate system, then install recommended amount by weight.

[White951]

Scott,

Me again. Is the low pressure port that is used for pressure testing on the 86 951 also used for charging?