A/C Charging Write-Up??

[MPDano]

Since the summer is quickly approaching, one of my projects is to get my A/C working on my car. When I try to turn it on from the HVAC Controls, nothing happens on the compressor (clutch engage). I was going to try and fill it up with some Freon, but need some guidance. I was told there is a way to jump the switch in order for the clutch to engage, etc, etc.

[Danglerb]

You need to pull a hard vacuum on the system for at least an hour to remove moisture and make sure it doesn't leak, and you need a new filter dryer anytime the system has lost pressure.

I don't think the compressor runs if the pressure switch isn't happy, no idea what could get screwed up if you run it with no freon or oil by jumping the switch.

[MPDano]

I am unsure of any pressure loss as I never disconnected the system. I just let it hang there during the engine swap.

[Danglerb]

How long has it been since it was last running?

Hook up an AC manifold set of gauges and see what you have got?

[MPDano]

I have no idea Mike. Got the car (engine seized) in 2007. Last failed smog attempt was 2003. I'm going with at LEAST 6 years non-op. The only gauge I got is what I have from charging my other cars. I bet you got these gauges.

[Danglerb]

Only gauge I have came on the top of a can of 134 "stuff" from Walmart, $19 and recharged my wifes Lincoln ok last year, about to give it another dose.

I mean a set of pro gauges, like these Harbor Freight ... Sometimes the valves don't open, so use caution when relying on pressures indicated.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92649

[MPDano]

Hey, that's not bad, $40. I am sure mine has the old fittings (R12?), so I would have to get converter fittings too, correct?

[Danglerb]

Dunno on the adapters part, but could be they are the things in the bottom corners of the case? If you click on the link at the bottom of the description you can download the manual, and that should show whats included.

Any gauge, even the one on top of a freon can at Autozone should be OK to show if the system is still pressurized or not (without running it).

Sitting that long I'd be surprised if it still has pressure, and that means, vacuum pump, new seals, maybe rebuild the compressor (mine was $190 shipped with no core cost), etc.

[DMRK]

I think that if you run with out freon by jumpering you could ruin/seize the compressor as I believe the freon is also the lubricant.

[MPDano]

Ok, first thing is to see if there is ANY pressure in the system, correct? If so, I will take a look at the gauge I have from my freon refill.

[MPDano]

Originally Posted by DMRK

I think that if you run with out freon by jumpering you could ruin/seize the compressor as I believe the freon is also the lubricant.

I think the idea was to jump the switch in order to add freon/lubricant to the system. Will do a pressure test first.

[rjm65]

I was at HF last Sat, I think those gauges on Mike's post are on sale right now.

You can find the adapter fittings at most autoparts stores. I have one of the cheapie HF vacuum pumps, let me know when you need it.

[928 Bro]

Don't jump anything, Once you can pull a vacuum and it holds you know there is no lacks. If it is extremely slow buy the 134a that has the lack stop it works.Do change the dryer and when you are ready to charge unload the first can of 134a and then turn the car on and the a/c and put the rest. There is a safety to protect the compressor but once the pressure of 134a build up again it should start work unless you have another problem. I hope the clutch engages. Good luck

[devilinblack]

Originally Posted by 928 Bro

Don't jump anything, Once you can pull a vacuum and it holds you know there is no lacks. If it is extremely slow buy the 134a that has the lack stop it works.Do change the dryer and when you are ready to charge unload the first can of 134a and then turn the car on and the a/c and put the rest. There is a safety to protect the compressor but once the pressure of 134a build up again it should start work unless you have another problem. I hope the clutch engages. Good luck

That's fine, but what if the system never had the oil from the R-12 flushed out of it?

Rob posted over on RL that he has a lot of the tools needed for this work, I was thinking of getting in touch with him and seeing if we could do an AC party sometime soon. I know I'm going to want to get my AC installed and working before summer. Before that though I want to have my hoses rebuilt and have a new dryer on hand.

[928 Bro]

I don't know about the 928 compressor(I Think is typical with most cars) but I have done three different car of mine and never had to worry about flushing the oil, I just made sure that I both the can of 134a that added more oil to make sure that the compressor had lubrication, especial if it hasn't ran for so long.

[Danglerb]

Two ways to look at the AC on a 928;

Its always going to have trouble, so just get it working and charge it again each year etc.

Fix it right, do all the stuff your supposed to do, hope for the best.

Pelican is a dandy place to buy the receiver dryer as well as a 134a upgrade kit (hint even if you run R12 its a full set of high quality replacement seals). Lot of people suggest replacing the expansion valve as well.

Rebuilt compressor from a few sources is about $200 shipped, bad hoses can be rebuilt locally, but a new condenser or expansion coil costs some bucks.

OTOH roll down the window and drink something cold. I'm thinking about removing the AC on my black car (track wt).

[911blex]

Don't try to bypass the a/c low pressure switch as you will destroy your compressor if it isn't already destroyed. The whole purpose of the a/c low pressure switch is to prevent the clutch from engaging so that you don't burn out your compressor if the pressure gets too low. This is the same reason why it is foolish not to replace the $15 a/c low pressure switch when you install a new a/c compressor because a faulty a/c low pressure switch could cause your clutch to engage when the pressure is too low, blowing out the seal on your brand new compressor.

Since your a/c system hasn't been converted to R134a yet, I recommend leaving it R12 unless you are patient as an R134a conversion takes a lot of time to do right and are in the mood to spend a lot of money as you will need to replace a lot of items to do an R134a conversion right. In addition, R12 cools better, doesn't leak as easily as R134a (molecules are much larger), and R12 is much more forgiving than R134a (maintaining accurate refrigerant levels isn't as crucial for the system to work well). Real R12 can still be easily and inexpensively obtained on ebay and at swap meets so the excuse that R12 is no longer available or too expensive is not valid.

However, if you are hellbent on converting to R134a, at minimum you will need to:

1. install R134a high and low service port adapters
2. replace all your old rubber o-rings with the green nitrile o-rings designed for R134a
3. replace your expansion block
4. replace your receiver/dryer
5. remove your a/c compressor, drain/flush the old refridgerant oil out, and refill it with PAG oil
6. vacuum all of the air out of your system after putting everything back together
7. leak test the a/c system
8. carefully refill your a/c system at 85% the amount you would with R12. As previously mentioned, R134a isn't as forgiving as R12. If you are more than a few ounces too low or too high your a/c system won't work right. You can't "top off" or "give a shot" of refridgerant to an R134a system like you can with R12.

If you wan't to do your conversion right, you will also want to:

1. replace all a/c refrigerant hoses with correct "barrier hoses" as R134a will leak out of your old R12 hose material and at the end fittings as they aren't crimped the right way to keep R134a from escaping
2. Install a new a/c condenser designed to deal with the smaller molecules of R134a

The bottom line is that an a/c system is only as good as it's weakest part so it doesn't pay to cut corners. If you aren't going to do it right, don't bother messing with it.

I did a complete R134a conversion on my '88 928 S4 that works great and still have several other old vehicles that have perfectly functioning R12 a/c systems so please feel free to PM me should any questions come up.

[entropy]

If you're budget is limited it can be simpler. The above thread is very technically correct, but in reality you could buy a cheap 928 for doing everything perfect. R134 is a smaller molecule and will slowly (and I mean slowly) leak. It is supposed to be updated with PAG oil, but I've never seen a problem with old oil like the guidelines suggest. Freon carries the oil with it to lubricate the system, including the o-rings at the joints. Since the compressor is the lowest point, and has it's own oil bath, you can send 12 volts to the connector to see if it kicks on ok. It won't hurt it to run 5 or 10 seconds. If it passes, by the guages above and a vacuum pump for $80 from harbor freight and a set of adapter fittings from somewhere like autozone. If there's moisture in the system (receiver dryer etc.) a long enough vacuum will boil the water out. If you're not in a hurry leave it on for 45 mins. or so. When you're done add freon and see if it runs. Unless you have a substantial problem, it's cheaper to buy a can and top it off once or twice a year. Don't turn the freon can upside down while charging. The liquid injestion can hydrolock the compressor. Make sure you charge it thru the low side (big tube) fitting. It can be a pain sometimes to get all the freon out of the can so you might want to have a blowdryer nearby to warm the can with to get it all out.

[entropy]

When you start trying to use the compressor, if the pressure goes insanely high quick on one side and really low on the other the expansion valve is probably stuck. It may have a piece of sand stuck in it from a ruptured desicant bag in the receiver dryer. If that happens replace them both. If it stinks like freon inside the car you probably need an evaporator core...which means you're screwed.

[Danglerb]

I seem to remember something about turning the compressor a few times by hand with the belt disconnected, but that may just be for a new compressor.