Can someone give me (or direct me to) a step-by-step precedure for recharging my R-134 A/C system on my '93 945T? What tools (guages, etc.) do I need?

I've seen a "Complete Recharge System" -- at Target of all places -- that includes a guage, tubing w/ fittings, and 2 cans of coolant (for about $15). Is this the way to go?

Thanks in advance.

Jeff Pierce
--
'92 Mercedes 190E (my daily driver), '93 945 Turbo (a kickass family car), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece)

I am not a regrigeration technician, but I have gone through this situation, and I offer my opinion. It is worth at least the price I ask for it, so use your judgment.

I will assume that the "Kit" you buy has a hose with Quick
Disconnect at one end and a threaded fitting on the other end that fits
either the Gauge OR the Valve, but NOT both at the same time (Professional gauge sets have TWO gauges and can have the gauge AND the Valve/Refrigerant connected at the same time).

1) If your system has completely lost its charge, and air has entered the system, then DO let a shop do the job if you've never done it and/or don't have the right equipment.

2) If your system is just down a bit on refrigerant (You say you already have an R-134 system), then air has NOT entered your system (since internal pressure is still WAY above atmospheric pressure), so there is no compelling reason to evacuate your system IMHO (unless you have a significant leak you wish to troubleshoot that will require "breaking" the system open).

A) Just buy the kit (get the one with the gauge) and hook it up as directed on the low pressure side (the one on the suction side of the compressor pump). It will read about 100-125 psi with a partly filled system with the engine not
running.

B) Start the car and turn the AC on max cool and read the gauge. If it's over 50psi, then you have a full charge and your problem is elsewhere (bad expansion valve, bad low pressure switch, bad clutch, bad compressor).

If your pressure reads under 40psi, then you can add some R-134.

Do this by:
1) Disconnecting the hose from the low pressure fitting.
2) Unscrew the gauge from the hose.
3) Connect the valve securely to the can of R-134 (MAKE SURE THE VALVE
IS SCREWED FULLY COUNTER CLOCKWISE-Unscrewed)
4) Connect the valve and can to the hose.
5) Connect the hose to the low pressure fitting again.
6) Start engine w/ AC on high.
7) Screw valve completely clockwise (to puncture can seal), then
counter clockwise to release R-134 from can. The can should be
held upright if only regrigerant is used, or inverted if you
are using R-134 with oil/leak check/O-Ring conditioner added.
The can should get quite cold as its internal pressure drops
(This is why the AC system works, by the way).
8) If you read approx. 25psi initially, add a full can (12-15 oz)
then recheck pressure as above. Be sure to disconnect the hose
from the fitting before unscrewing the valve and replacing it
with the gauge.

If you read close to 40psi initially, add approx
1/2 can of R-134 (close the valve fully when the can "feels"
about half empty and recheck the pressure. When the pressure
reads about 45psi, add no more R-134. You can save the remainder
of the can for later use as long as the valve is closed tightly.

I hope that helps some. If your system loses efficiency over a winter on non-use, or over a few months of summer use, you probably have a very small leak. You would have to spend about $75 at most shops just to have gas added (as above), or considerably more ($75-500+) to have the small leak diagnosed and repaired.

I see adding a can of refrigerant occasionally (at about $5 for 12oz) yourself as a cost effective way of maintaining a useable AC system. R-134 is supposedly safe for the environment, so losing a few oz. per month is not a disaster IMHO.

Good luck and let us know what you end up doing.

Bob

I am a certified technician (ASE Certified) so I know of what I speak.

First, I don't believe any amateur should mess with safety related equipment, which includes brakes, SRS(air bag and SIPS), as well as the AC system.

The AC system operates at hundreds of pounds pressure, and if an amateur connects a "WalMart Special" kit to the wrong port, the equipment could exploder and badly injure or kill the shade tree mechanic. Most amateurs don't know the difference between a can of R134 and a can of Pringles chips, and trying to use the wrong refrigerant or lubricant can cause thousands of dollars damage to a system.

The poster to who I reply also neglected a basic safety procedure that is absolutely essential, and that is to wear eye protection while working around any dangerous mechanism. He also neglected to advise that the electric cooling fan could come on at any time while the engine is running, and is a hazard to careless fingers.

Most shops only charge $100 or less to do a check of the AC system, and that is money well spent by the home tinkerer. I spent years learning my trade, as did my fellow technicians, and it is false economy when working on an expensive piece of especially cdomplicated machinery to skimp on a hundred dollars.

Let a Pro do it right for you.

I think "BobbyC" gave very practical advice! Not only that he was taking a fair amount of his time to write the advice.

You make a good point about the eye protection but almost every task on a car calls for it so the fact that he didn't mention it isn't a big deal. Ever get a piece of greasy sand in your eye while under the car?

We have to assume the people asking for advice have the inteligence to judge their own capabilities if this site is to be of any value.

MHO & $0.02
--
'96 965 with 16' wheels at 103K. Had '85 745 Turbo Diesel for 200K.

Come on guy, you act as if everyone is an absolute idiot.

That's nice that you have exaulted yourself with the extreme title of "ASE Technician PoBah," but frankly that doesn't come with a license to preach, or try to scare others.

There are lots of people who are plenty smart and plenty experienced to tackle what you are paid to do. There are plenty of others who would be wise to pay for service.

This board is a great place to exchange ideas, but not to try to impress or to instill fear. Respect for pitfalls maybe, but not fear.

Bob

The first thing you should get is the Volvo green book if you are serious about doing it yourself. Then you will need a good vacuum pump rated for A/C use and a set of gauges. Pump about $300, gauges about $40. ("Google" to find the best prices.) Also you will need the proper "PAG" oil to put in with the charge. Don't crap-up your system with the "universal" Ester oil in all those aftermarket kits.
--
'96 965 with 16' wheels at 103K. Had '85 745 Turbo Diesel for 200K.

The "complete recharge system" is the way to go, if you want to destroy your A/C system.

I have posted a million answers to this question before. the FAQ has got to have information about A/C charging.

To completely recharge, you have to evacuate the system (evaluate for leaks) and thereafter charge with the correct weight. If the system is evacuated, you can determine the weight with a scale and go from there. But topping off a system that has a leak, is totally unscientific and will yield less-than-optimal performance.
--
Chris Herbst, near Chicago.

OK, so this sounds like something that is best left to a professional.

In your experience, Chris, is this something that any decent A/C shop could handle, or do I need to go to a Volvo-specific tech?

Again, thanks in advance.

Jeff Pierce
--
'92 Mercedes 190E (my daily driver), '93 945 Turbo (a kickass family car), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece)

The 940 is a simple and common A/C system.

You could easily do the procedure yourself. If you can vacuum the system out, you can charge it. But if you charge into atmospheric pressure, the system won't be very good. If the system leaks and you recharge it, you'll always be chasing an elusive charge/no-charge situation, where the level won't be right. So my caution is that the system has to be leak-free before charging or it will never have the right charge level for more than a little while, and you'll have a rotten A/C system despite constantly chasing down the proper charge.
--
Chris Herbst, near Chicago.

How do you vacuum the system out? I have a simple hand-powered vaccum pump -- is that sufficient?

Jeff Pierce
--
'92 Mercedes 190E (my daily driver), '93 945 Turbo (a kickass family car), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece)

No. You can pay someone to do it, or rent the equipment, or whatever. It needs to be a long-running vacuum pump, because the system has to be held at a deep vacuum to get out the moisture.

You can still do the charging once the system is empty. Just make sure you have a good measuring scale to see how much you're putting in. ANd monitor vent temps as you charge. The vacuum in the system draws in a lot of refrigerant to begin with, and the rest it will draw in once it gets running.
--
Chris Herbst, near Chicago.

A/C takes a special vacuum pump. The pump needs to be fitted to A/C gauges so the new R-12 or whatever can be transferred in while system is under vacuum. The vacuum will also alert you of any leaks early on. This should eliminate the need to send in costly refrigerant with a leak present. As Chris stated, you just need the right equipment. Note: The vacuum will pull down around 30Hg.

Look here;
http://www.jcsonlinetoolshed.com/subcategory/ac/vacuum-pump.asp
--
'96 965 with 16' wheels at 103K. Had '85 745 Turbo Diesel for 200K.

Your mention of leaks makes for a good transition to my next set of quesitons:

It would seem to me that the need for a recharge is an indication that the system has a leak. Is this correct?

My research on this subject has revealed that the schrader valves are a common place for a leak -- and since they're cheap/easy to change, then it might be a good idea to change them when you do a recharge. Yes or no? If so, then I would assume you evacuate the system, replace the valves, then re-apply the vacuum, and proceed with the recharge.

Forgive me if all this seems pedestrian. I really do appreciate your help.

Jeff Pierce

--
'92 Mercedes 190E (my daily driver), '93 945 Turbo (a kickass family car), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece)

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Yes, though most AC shops recommend replacing the receiver/drier anytime the system is opened up.

Bob