Air Conditioning Removal / Replacement

Last updated: September 13, 2000


Date: Tue, 12 Sep 2000 21:41:16 -0400
From: Tom Walsh (

First some A/C background and theory:

The system is a closed system meaning that it should never have to be recharged. Having said that... You should never have to recharge the system. If you have to recharge the system then you are leaking freon (or R134A).

The system works very simply. The freon in the system is compressed in side the compressor. Anytime a gas is compressed (whether it is air or freon) the gas heats up. So now we have compressed gas in the A/C lines... This is know as the high pressure side.

The compressed gas enters a dryer where it interacts with a silicate and that absorbes any moisture that might be contained in the gas.

From the dryer the gas travels to a condensor. This is the mini radiator located in front of the main radiator in the mouth of the car.

From there the gas travels inside the car under the dash where it reaches the evaporator core. As the gas enters the evaporator core it pass through an expansion valve. Here is where the cold comes from. The high pressure freon goes from a very high pressure (I believe in the range of 200psi) to a low pressure gas (I belive in the 60 or 70 psi range but don't quote me that). When a gas goes from high pressure to a low pressure it becomes cold (this is a lesson in physics... It absorbs heat from the surounding area). The gas is then routed through the evaporator core. Then an internal fan blows air through the evaporator (it is basically another radiator). As the air passes through the evaporator core it cools off... And then is routed through the ducts in your car and then it blows on you.

The gas is then routed through pipes (this section is called the low pressure side) back to the compressor and the process starts again.

Now on to trouble shooting your problem:

>The air conditioner in my third has not been cooling at all in a while.  I 
>decided to get it repaired.  The technician said that it first needed just 
>coolant.  I have a 93 so he was going to use R-12 but then said he had a
>product called Duracool that he could use that would work just the same as
>R-12 but is much cheaper.  I said O.K.  Of course it didn't work.  So he next
>says you need a new Dryer for the system.  Again I say O.K.  I get the car
>back, and he tells me, its cooling on high at 65 degrees F.  The normal high
>cool is 50 degrees F or so.  He then says I need a new compressor for the
>system.  The one in the car now is bypassing on the low side he says.
>The Mazda part cost a fortune and their are not any aftermarket/rebuilds
>available so I was upset.  I went to Mazmart in Atlanta and found one
>from a wrecked 93 that only had 13,000 miles at the time of the wreck.  I took
>it to my guy and he installed it.  The compressor is operating perfectly but
>it is still not cold.  He says I need an expansion valve.  They told me it is
>located behind the glove box in the dash.  My question is...  Does this
>make sense to people who understand how air conditioner's work??  I have no
>idea and was curious if this makes any sense.  I feel like I am going to have
>a patchwork A/C system before too long.

One of the main ways an expansion valve can become blocked is through the silicate in the dryer. It is like little beads and they can block the valve from doing its job. It is possible that this might fix your problem. I am not familiar enough with the coolant gas you are using though. It is possible that the system is not large enough to hold enough coolant gas to cool your car efficently. Even with R12 the system was inept at best.

_______________ From: (
Sent: Thursday, July 19, 2001 11:10 PM

> Well, the pinheads at Schaumburg Mazda, despite being woefully
> mis-informed about a number of things, claim to have the AC fixed.  
> The guy said it was simply low on freon and that no leaks were detected.
> This really does explain how it could work a couple of months ago, and now
> not at all, but that there are no leaks.  (sarcasm - where did it go???)
> I also guess that the compressor needs to have freon in order for the
> magnetic clutch to engage.  When I would hit the AC button, the compressor
> would not engage.  That I am not really sure of, but I before this I would
> have bet money that the mag clutch would have engaged, but it simply would
> not have had any freon to work with.  But according to what they are
> saying, it must need freon to work.  Maybe there is a sensor that prevents
> the mag clutch from engaging if there is no freon.
> I'll obviously check this before leaving the dealer tomorrow.
> I deserve this for even bothering to go to the dealer.  What a crock of
> shit!!!  I am going to see if I can cancel the extended warranty and get
> the money back.


From: Ashraf Farrag (

> Well, the pinheads at Schaumburg Mazda, despite being woefully
> mis-informed about a number of things, claim to have the AC fixed.  
> The guy said it was simply low on freon and that no leaks were detected.

Liars. If the freon is low, it HAS A LEAK!!!!! Let me re-emphasize: If the freon is low, it HAS A LEAK!!!

I had mine filled after some body work was done, and wham! Two days later in the summer, no A/ freon left either (none, nada, zip...) Their A/C tech is on crack.

My 10 year old Honda (bought new by my dad) has NEVER needed freon, and continues to work as freezing cold as the day bought new. If it lost freon (which you do....but just a little bit....not enough to cause it to go low like that) then it will continue to lose freon.

They need to do pressure/vac check on the system and run a sniffer on the couplers. You can check yourself, if a coupler has grime on it, it is probably compressor oil leaking and hence dirt attaching to it.

The A/C system DOES have a pressure switch, where if the pressure is too low, the compressor's clutch will not engage. If the switch failed, that is another story, but if they added freon (good for them - expensive parts, 10 minute procedure to bill warranty company) then you are probably gonna lose it AGAIN...

Any decent mechanic knows if an A/C system is low, it has a leak, and needs to be taken care of. In fact, their tech isn't supposed to fill up the system to check for leaks. Check out and look at the refrigerant certification study guide. Tsk, tsk, tsk. (I may be off base on this one....but they shouldn't be doing what they are doing, and know better, since they are certified, even if your state doesn't have laws prohibiting this specifically)

By the way, this is all very standard stuff, and doesn't have anything to do with FD specifics AT ALL... A/C systems are very similar and there is nothing rotary/FD specific/or magical about yours.

I hate to say it, but we've come to the conclusion that only the lowest guys work at dealers, making barely above minimum wage (for the most part). The A/C cert can be had with a $15 fee over the internet via above site, only studying the 12 page study text. You can buy R-12 yourself after that ;-)

How do I know? Got a buddy that I pointed in that direction, and his cert is in the mail. Mine will be too when I get around to finishing other stuff...

Time for Steve to start harassing up the corporate chain and get some real results.

Maybe Mazda will implement a darn 5-star program like Dodge/Chrysler.

Don't be surprised if your A/C dies again on your trip. Have them check the pressure on the system before leaving and compare to the last pressure they filled at. They should be able to correct for temperature difference across two days. I'll bet it has already leaked out a good portion. It only takes a few minutes to do that, and an A/C sniffer can pinpoint a leak. Definite must tool for a dealer doing A/C service work!


From: Chris Davis (

A word of caution. The AC system is an entirely closed system. If it was low on freon then it HAD to leak from somewhere. And yes there is a sensor that detects both a high and low pressure level in the system. It's called the AC pressure regulator (ta da!! :) ) The regulator disengages the clutch to prevent damage to the AC in the case of overpresuurizing or not enough freon (low pressure). I just had my car taken in for a third time to find out that the compressor itself was leaking. The UV die (which was put in during the first recharge) finally showed up the third time. It was a very slow leak but it eventually showed up. I know some people will say that freon leaks out of the rubber hoses overtime and that every system eventually needs recharged which is true but..... my 1987 Nissan 200sx which was 14 years old (may she rest in peace) never lost any detectable amount of freon. The AC worked up until the day the junk yard took it away (this year).


From: (Rommel)

If you're low in freon (R-12) you have a leak in the system,by passing the pressure switch won't help coz it will blow hot air too or your evaporator will freeze up half way coz of low charge.. The leak needs to be repaired. Have the dealer put die in the system or pressurize the system with nitrogen since oxygen is bad to use. If it's a tiny pin hole leak you might be able to recharge it but the charge will eventually go down after time. R12 is hard to find now days it's phased out.


> I installed my PFC and the AC refused to work, so I
> did Chuck Westbrooks AC fix of bypassing the ECU and
> everything seemed to work great for one day.
> Now, starting last night, the AC will run and get
> extremely cold and then shut off and blow humid air.
> I have to turn the fan off and then back on to get the
> AC to kick back on.  Sometimes I have to turn it off
> and on a few times for the AC to come back on and
> other times it makes no difference how many times I
> turn the fan off and on.
> Both last night and today I was able to get the AC to
> stay on with the fan set to 4, but I don't know if
> this is a fluke or not.
> Does it sound like I need a recharge, is the AC
> freezing up, have I missed something else?
> Even when the compressor cycles off the air shouldn't
> get humid like it does, so what am I missing here?

Date: Sat, 25 Aug 2001 14:41:51 -0700 (PDT)
From: Chuck Westbrook (

If your AC gets extremely cold then cuts off like you said, it sounds like your AC thermoswitch is not working properly, or your freon is low. Since I did this mod and had my freon recharged (first time since buying the car 9 years ago) my AC has worked better than when the car was new.


Date: Sat, 25 Aug 2001 20:26:23 -0400
From: "Ashraf Farrag" (

I can't speak for the PowerFC issues, but I'll chime in on the regular A/C stuff.

> I installed my PFC and the AC refused to work, so I
> did Chuck Westbrooks AC fix of bypassing the ECU and
> everything seemed to work great for one day.
> Now, starting last night, the AC will run and get
> extremely cold and then shut off and blow humid air.
> I have to turn the fan off and then back on to get the
> AC to kick back on.  Sometimes I have to turn it off
> and on a few times for the AC to come back on and
> other times it makes no difference how many times I
> turn the fan off and on.
> Both last night and today I was able to get the AC to
> stay on with the fan set to 4, but I don't know if
> this is a fluke or not.

Sounds electrical/control issue. The ECU shuts off the A/C at high RPMS via a relay, so the PFC may have it's fingers in that mechanism.

There are several things that run the A/C:

This is from memory, but should be fairly comprehensive.

> Does it sound like I need a recharge, is the AC
> freezing up, have I missed something else?

Obtain/borrow/pay for a set of A/C gauges and see if your system is performing correctly. If it worked before, it is quite doubtful that it suddenly stopped working at the same time the PFC went in. Freezing up can be detected by abnormal pressure on the gauge set. See if the A/C works at idle with a stock ECU...quick and easy, and you don't have to deal with looking at any A/C components - blame the obvious - what you changed and made A/C an issue!

> Even when the compressor cycles off the air shouldn't
> get humid like it does, so what am I missing here?

Nope, it shouldn't. Start checking fuses driver's panel and under the hood. That is a good place to start. Then the A/C relay. Then the compressor magnetic clutch and freon pressure.


This was written for the 2nd gen, but looks like it should apply to the 3rd gen as well. Let me know if it doesn't. --Steve

Date: Wed, 10 Jun 1998 07:42:56 -0700
From: "McCurdy, Michael"

Replacing the A/C compressor on any car is a major job. Mechanically, it is not very challenging, but the procedures and equipment required to evacuate and recharge the system are complex and expensive. The following is a brief synopsis:

1) Evacuate existing freon. Legally, this needs to be collected for recycling.

2) Remove compressor and accumulator/dryer.

3) If the original compressor was disintegrating internally, the entire system will need to be pressure flushed with an environmentally unfriendly solvent to remove all traces of metal debris. The expansion valve will need to be removed and cleaned (or replaced). If you don't do this, the new compressor will only last a few weeks or months, and the system will only cool until the expansion valve is clogged with metal fragments. If the compressor you remove is merely leaking, you can skip this step. However, it is wise to drain the oil from the compressor onto a white paper towel. If the oil looks like clean, light motor oil, you're OK. If there is any particulate in the oil, or if it is dark or discolored, you're SOL. If you do flush the system, you will have to add a specific amount of new oil for each component flushed before reconnecting the system.

4) Install new/rebuilt compressor, verifying that it has the correct amount of oil in it.

5) Install new accumulator/dryer, verifying that it has the correct amount of oil in it.

6) Immediately evacuate the system with a vacuum pump, and verify that it will hold a vacuum.

7) Recharge system with R-12 (expensive), R-12 replacement (unknown performance), or the new R-134a (not as good as R-12 in older systems).

As you can see, this is a lot more work than replacing an alternator or water pump. If you have a friendly shop, you can probably do most of the mechanical work yourself, then immediately drive it over for an evacuation and charge. This may save about half the cost versus them doing the entire job for you.


Date: Mon, 13 Jul 1998 23:01:16 -0400

When replacing A/C components, replace every o-rings whose seal is uncompressed. This includes brand new o-rings which were just compressed on a seal, but which needs to be uncompressed for whatever reasons. In other words, A/C o-rings should be considered as compressible only once.

R-134a Conversion

I have a brochure from the Pep boys that describes how to do this. I scanned it in (OCR) below. I edited it a bit to fix grammar and spacing issues. --Steve

Retrofitting R-12 A/C Systems to R-134a Refrigerant

Please be advised that it is now recommended and economical to convert any vehicle's air conditioning system to R-134a refrigerant (the refrigerant in new cars) when any major A/C system parts are replaced. (I am assuming the economical part refers to a major component failing and factoring in the cost of this replacement when determining overall economics. --Steve) These include but are not limited to:



The charges for the adapter fittings, stickers and Ester oil are the only extra cost when the conversion is done during major component replacement including accumulator or receiver/dryer. The difference in refrigerant prices between R-12 and R-134a will more than offset the additional cost in most cases.

The production of R-12 ended on December 31, 1995. The end in production has resulted in shortages and escalating R-12 prices. We believe that retrofitting protects our customers and our environment by outfitting vehicles with a less expensive refrigerant that does not harm the earth's protective ozone layer.

Pep Boys

3111 W. Allegheny Avenue . Philadelphia, PA 19132


Date: Mon, 3 Aug 1998 16:16:51 -0500 (CDT)
From: Terry Loveless

> Please note that the new substitute R143a could run your compressor very hot.
>I refilled with R143a just few months ago, now my compressor has given up his
>life. Right, it was fantasitc cold, a lot cooler than when I have R12 because as a
>home mechanic, you could always refill beyond the recommended amount of freon.

That's why the instructions tell you to only fill it to 80% of it capacity. A R-12 system converted to 134a DOES run hotter and at 80% it WON'T cool as well as it did with a full charge of R-12. That's also why you need to start with a vacuum pulled on the system and pay close attention to the gauges. Don't compromise comfort for mechanical reliability, unless you like the idea of changing out compressors.


Date: Mon, 06 Jul 1998 08:55:54 -0500

It is typically accepted that R134a will not function well in an R12 system. The cooling coefficient for R134a is lower than that of R12. Additionally, the lubricating oils in the two systems are different. R12 uses mineral-based oil, and R134a uses a polyol ester. When mixed, they form an acidic goo that can ruin pretty much all of the a/c system. On top of that, it has been recommended that R134a only be used if the hoses are barrier-type hoses and the "O" rings and seals in the system made of silicone rubber, so they will not leak the new refrigerant.

A more friendly approach to the car owner MAY be the use of R406a, which uses mineral oil, and actually cools better than R12. The hoses will need to be changed, but I believe that the seals and "O" rings can stay (if they are serviceable and not made of butyl rubber). This refrigerant is not as well known as R134a, and may be more difficult to find. It is also a blend of several refrigerants (called and azeotrope), and so must be filled into the system properly to ensure a correct mixture.

But then, you may just decide to use R12 anyway. Cost-wise, R12 is expensive because the eco-nazis have placed a giant tax on it. R134a is expensive because the lubricants are expensive. R406a is expensive because it is uncommon. What you would want to consider is whether you want to or can manage to convert any necessary hoses, seals, and "O" rings.


James Willcox
07/17/98 03:38 PM GMT

For $27, J.C. Whitney sells a kit to convert to R134. Their web page tells all about it. I haven't used it yet, but I remember seeing it in their catalog.


Date: Thu, 11 Jun 98 07:13:31 -0500
From: "Linthicum, Sandy"

Check out this site.


Date: Thu, 11 Jun 1998 18:03:59 -0400
From: Jay Wallace

One other site to check out.

Weight Savings from Removal

Date: Tue, 14 Jul 1998 13:23:10 -0400
From: David Breslau

I just did this two weeks ago, and did not check temps with any instrumentation before or after, so all numbers are WAG's, but here goes...

>1. What kind of weight savings would be involved? (I suppose this depends
>on whether I did a partial or complete removal of the various a/c pieces.)

If you just remove the condenser (all I've done to this point), you'll save ~5lbs. If you take out everything but the heat exchanger under the dash, I think it would be ~75-90lbs.

>2. Would this tend to improve radiator cooling? A significant or
>insignificant "degree"?

Perhaps by 10% compared to AC off, much more if the AC was on and working hard.

>3. Would this facilitate the installation and operation/efficiency of a
>larger intercooler?

Others can answer this better, but I would guess so, if you're willing to relocate the radiator (as Trev has done).

>6. How difficult is this undertaking? To really take advantage of the
>change, would I be looking at a lot of fabrication of ducting? Depending on
>the level of modifications, would I be advised to channel the air-flow in
>such a way to improve the intakes, intercooler, radiator, or oil coolers?

Have the freon drained by a dealer or professional AC shop (DON'T vent to atmosphere). You then have to remove the lip spoiler and belly pan to get to the condenser. This can be a little tricky if the 6mm clips that go into the various body parts have started to rust to the bolts.

After the panels are out, there's a few bolts holding the condenser in, and the two AC lines to disconnect. A couple of 10" adjustable wrenches will easily break these loose. The smaller of the two fittings has a groove running around the nut that make it look like it's a left hand thread, but it's really a standard right hand.

If you might want to reinstall the condenser later, leave the lines in place, but cap them off. An AC shop should have the proper threaded end caps to do this right, I've just got plastic caps on mine ATM. The drier can be damaged if it's constantly exposed to humid air.

I haven't looked into whether the AC compressor will run without freon in the system, if there's no interlock, then the compressor can be damaged if it's switched on.

Mold Smell Cure

Date: Wed, 12 Aug 1998 10:24:58 -0400
From: "Cassada, Lewis"

This will fix the wet towel smell (mold, mildew, etc)...

BG Frigi-Fresh is formulated to quickly and effectively remove foul, musty odors from automobile air conditioning systems. It kills mold, mildew and other odor-producing organisms that grow in the evaporator core and housing. Powerful deodorizers in BG Frigi-Fresh keep the automobile interior smelling fresh and clean.

EPA Reg. No. 44446-20-67145
Part No. 708


Date: Wed, 12 Aug 1998 10:22:12 -0400
From: "Luis A. Loimil, MD"

I also saw on TNN that you can spray regular aerosol Lysol in there and it will do much the same thing.

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