924Board.org

[ideola]

OK, with warm weather (sort of) on the way, one of the few remaining projects on my to do for the NA is to get the AC up and running. So, here are some questions.

1. The compressor I have is not frozen, however, I'm not getting 12V to it. There is a black wire that comes out of the firewall and travels along the driver's side wheel well, and then attaches to the compressor just under the airbox. It has one of those plastic protector things over the male-female spade connector. I snipped off the female portion, which attaches to the lead coming from thru the firewall, and recrimped a new connector. When I turn on the AC switch / fan control, I do NOT get any voltage at this connector, so something between the firewall and the switch must not be functioning. Any suggestions as to where to start looking?

2. When I turn on the AC switch, both electric radiator fans engage immediately. I suspect this is to help keep the engine cool under the extra load caused by an engaged compressor, but I want to confirm that this is normal behavior.

3. I picked up a brochure at Murray's about their AC recharge kits. They claim they have a kit you can use that will recharge an old-style R12 to R134 with no conversion necessary, provided the original system is evacuated. Can this truly be done? Also, is there any obvious way for me to tell if the system has already been converted to R134?

TIA
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erstwhile owner of just about every 924 variant ever made

[Smoothie]

1 - There should be a pressure switch on or near the receiver-dryer. If the system has lost its' charge, that switch will stay opened to keep the compressor from turning on. The connectors to the switch can be jumpered to see if you then get power to the compressor, but don't run it for long because it needs oil which may be gone if the system isn't charged.

2 - That's normal.

3 - Evacuating the system for an R134 changeover probably also includes removal of the R12 oil (I have a vague recollection of hearing that R12 oil isn't compatible with R134 oil), but it definintely includes removal of the R12 gas & any liquid, followed by "boiling" all moisture out of the system by the use of a vacuum pump run at something like 30-35"Hg for something like 30 minutes. Soon after the system is evacuated and I assume the optimum state is while it's still under vacuum (, but without the vacuum pump running or attached), you charge the system with R134 and its' oil. There should be R134 specific adapters included in the kit that get attached before the R134 is added - these might have to be added before the system's evacuated depending on if the original Shrader valves are being removed from the old R12 fittings. (Most-all R134 adapters are designed to screw onto the old fitting without removing the old Shraders, but I've heard of problems that necessitated their removal.

2 pics of the receiver-dryer followed by 7 more of AC parts shot through the glove box opening - http://pg.photos.yahoo.com/ph/smoothies931pics/detail?.dir=/a174&.dnm=e0fc.jpg&.src=ph
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[gohim]

The black wire that comes from the dashboard that attaches to the ac compressor is the 12V+ supply for the compressor clutch. No 12V+ (between the wire and ground) means no power to the clutch, and the ac ckutch will no engage to turn the ac compressor (so no cold).

Turning on the ac system normally does turn on both radiator cooling fans.

The wire from the firewall runs to the pressure switch before it goes to the ac clutch. If the refrigerant charge is too low, then the low pressure switch will not allow the power from inside the car to run to the ac clutch and engage the compressor.

You can check to see if the refrigerant pressure has fallen too low by jumpering the two wires on the low pressure switch together, and listening and watching the compressor to see if the clutch engages and the end of the pulley spins along with the pulley (which always spins whether the ac in engaged or not).

All R134a conversions to R12 designed ac systems NEVER work as well as the R12 refrigerant did. There are conversion kits out there that claim that no other work or parts need to be replaced, but they do not work as well as a full conversion job, which includes the removal of the R12, removal of the R12 oil, flushing of the entire system to remove all trace of the R12 oil (yes it is not compatible with R134a oil and when mixture creates a sludge that will clog the as system), and replacement of the ac receiver/drier.

R134a gas particles are smaller than R12 particles and they will leak out of an R12 that does not leak R12. So more frequent filling would probably be necessary.

You can buy the stuff necessary to complete a proper R134a at home fairly inexpensively if you have a good ac strong compressor (capable of 5cfm or greater at 100psi or greater) to power a vacuum powered vacuum pump (Harbor Freight $15). You will also need a ac manifold gauge set with hoses (Harbor Freight on sale $45), and a R134a can tap (about $10).

[ideola]

Smoothie, you never cease to amaze! You are absolutely correct, as soon as I jumpered the switch, I got 10V at the AC hot lead (with the car not running and the AC fan switch in the 3 position). So it sounds like I just need an AC recharge/R134a conversion. Hmmm...should I attempt it myself or take it in? Decisions, decisions.

Thanks!
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erstwhile owner of just about every 924 variant ever made

[ideola]

Oh, two more things...
1. Is there a way to tell if the system has already been converted to R134a?
2. Is there a write-up anywhere for a DIY R12 to R134a conversion?
_________________
erstwhile owner of just about every 924 variant ever made

[924guy]

this is on my list too, ive already got a new reciever dryer, and a "conversion" kit which contains all new sealing rings for the hoses, and adaptors for the valves. ill probably have a shop empty the system of r12, then install allthe new seals and r/d myself, and take it back them for final purging and refilling with 134a , unless they give me a really good proce to just do all for me.. once the car is running again, itll be one of my top priorieties, it already getting hot down here...

if the car has already been coverted, there should be adaptors already threaded onto the fill valves..
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[kaffine]

If the retrofit was done correctly there will be a label indicating when it was converted to R134 and how much charge is required also the service ports will be quick disconects instead of threaded shrader valves that R12 uses.

Unfourtantly conversions are seldom done correctly. If there is any pressure left in the system then a shop can use a refrigerant dector to find out what is in the system if you can find a shop that has one and knows how to use it.
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80 924
80 931

The best desciption of an atom boils down to something unknown is doing we don't know what.
Sir Arthur Eddington

[Smoothie]

I think in a well done real retrofit they'd also replace the expansion valve with one designed for R134, right? It's at the inlet to the evaporator inside the car, separating the high and low pressure sides of the system. High pressure liquid refrigerant passes through the small orifice of this valve and cools as it enters the low pressure side, cooling the evaporator, etc., etc.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[gohim]

Each Different, Legally Registered and Approved, Refrigerant Gas has a Different, Registered Port. Usually this is just a different size, but same basic quick release connector.

You are supposed to be able to tell the type of refrigerant gas by the size and type of the high and low port connectors.

This is not always true, and a have seen numerous cars with one R12 connector, and one R134a connector. When I seen this, I assume R134a, because nobody would spend the money to install an R134a connector if they were still using R12.

Unfortunately, people fill ac systems with all kinds of unapproved gasses. Propane is even used by some unscrupulous shops. Yes, propane, that stuff we burn in the outdoor grills, and it does work to some extent.

Here is the U.S. I read that the laws are being changed so that commercial ac shops will be required to own and use a Refrigerant Detector to test the refrigerant and determine what it is before recharging because of this problem.

Many of the R12 substitutes being marketed are not approved by the EPA, and therefore not legal for use in automobile ac systems here in the U.S. If you are wondering if something that you have seen advertised, or someone is offering you at a lower price than R12, that is supposed to be the same as R12 is approved for use, you can check the EPA Website, which has a list of all approved refrigerants, and ther checmical makeup. Many of the unapproved R12 substitutes are actually R134a blended with a small amount of R12.

If the car were mine, I buy or borrow a R12 manifold gauge set to determine what is happening on the system, and if healthly, and low of refrigerant, simple buy some R12, and top the system back up. The ac systems in ours cars are barely adequate to begin with, and converting to R134a may make the ac totally inadequate for your local weather conditions.

[jpab924]

The trick would be to find someone who still has some unused r-12 sitting around. Even if you do, don`t expect it to be cheap.

[gohim]

Garage Sales in older parts of your town.

Everybody used to keep two or three cans of R12 in the garage along with the can tap. It only used to cost about $2 a can.

Most people switched to cars using R134a years ago, and the rising value of those forgotten cans is not know by many people cleaning out their garages.

Get up real early and scout out the sales for those piles of dirty old cans. You'll find brand-new unused bug spray, paint, motor oil, transmission fluid, AND if you're luck, cans of R12 for $1-$2 a piece.

You if you don;t have the time, go online, and take a test for a EPA Section 609 Certificate, and buy your R12 over the counter at your local auto parts store.

[ideola]