Muzz,

the heater core as well as the ac on my 90 GT went south and I made the decision to replace everything.

steve's heater core tip is a big help but, if you decide to replace your evap, you're looking at a little more work.
i can pm you tomorrow with info on how i changed mine......just let me know.

jkb

Muzz 66 wrote:

My Mustang Number 2 is a 1992 LX 5.0, 5-speed with 267,000 miles on the clock.  A/C hasn't worked in years, I've just lived with it.  No more.  I have no idea what went wrong with the system in the first place so I can't tell you.  I know almost nothing about A/C systems but I think a complete change-out of all my A/C components is in order.  The system was originally an R12 unit and I think it probably wise to get a system for R134, right? Most of what I'm reading says that 1992 era factory components will work just fine with R134. Is this accurate?  I plan on a heater core change while I'm in there changing the evaporator.  Any advice and hints are greatly appreciated.

Most R12 systems can be converted to R134a and they will function fine.  Whenever you're faced with a complex system that has issues, the easiest thing is to replace everything.  Instead, I suggest you pump down the system and find the leak.  It may be that when the system developed a leak, the low pressure switch was tripped and the compressor clutch shut off.  If you fix the leak and worst-case you discover your compressor froze up, you will likely have what is lovingly referred to as the black death strewn throughout your system.  If that's the case, you will have to flush it out, but that's far easier and cheaper than replacing the evaporator, and condensor.  Here's a link that provides a starting point:
http://www.corral.net/index.php/tech/maintenance/74-r12-to-r134a-conversion-on-1988-mustang-lx-5o
The article mentions a smart VOV.  I recommend you replace your orifice in any case, since it traps junk, but for a little more you can get better performance if you use the smart VOV.
 

I would just replace what was causing the leak and retrofit the car to R134 instead of re engineering the whole system. It's going to be decently cool, and better than living without A/C.

afnid wrote:

I am not a guru, just a few months into this, but I have a 1990 efi motor and was pretty excited that it had a much newer a/c pump and it should be so much better!

Wrong!  It is still a quarter century old and obsolete.  To switch to R134a you have to flush everything pristine.  Then the old a/c compressor will supposedly work, but it really can't handle the higher pressures of R134a and will never reach the full cooling potential.  Not sure if your car would have a parallel flow condenser, but thats what is recommended for R134a.

So I found this kit: http://www.latemodelrestoration.com/products/Mustang-AC-Conversion-Kits it is the only thing I found for upgrading the system, but seemed really pricey.  There are some mixed reviews, but those might have been early adopters.  I never asked if it was available piece-meal since the condenser probably wouldn't work, making it even more expensive in my case.

One popped up on craigslist so I went and checked it out.  The pump was a sd7 series, I would need to look up the number in my notes, but it is a good pump that can be bought new for $200.  A parallel flow condenser can be as high as $100 or so.  I read custom hoses can run $100.  The mounts raise the pump up and out a couple inches and you need a longer belt, but subtracting the other stuff, they are $350 all shiney black.  It is still for sale on craigslist..

So I bought a rebuilt Sanden compressor for $120, which I can make work on the oem bracket with a little fabrication; it should look like it belongs there.   Was actually looking at the mounting tonight.  Still trying to find the right condenser to fit my 24" radiator, but contemplating one with a built-in drier.  And that pretty much sums up where I am at on my a/c for under the hood.

I dsagree that a flush is necessary, unless the old compressor failed.  Also, if you're on a budget, you might be able to reuse yout old hoses.  Here is information that describes what is generally required: http://www.epa.gov/ozone/title6/609/technicians/retrguid.html

 

Muzz 66 wrote:

My Mustang Number 2 is a 1992 LX 5.0, 5-speed with 267,000 miles on the clock.  A/C hasn't worked in years, I've just lived with it.  No more.  I have no idea what went wrong with the system in the first place so I can't tell you.  I know almost nothing about A/C systems but I think a complete change-out of all my A/C components is in order.  The system was originally an R12 unit and I think it probably wise to get a system for R134, right? Most of what I'm reading says that 1992 era factory components will work just fine with R134. Is this accurate?  I plan on a heater core change while I'm in there changing the evaporator.  Any advice and hints are greatly appreciated.

Been there, done that with my 93.  I agree with Josh. Just replace everything using all stock components with R12.  Or take it to an ac shop and have them  do a vacuum test first and see if it holds vacuum.

Don't waste your time or money on one of those conversion kits for $34 that just change the fitting on the ac compressor and the fitting on the supply side hose so you can add freon .  If you install the kit on a bad compressor or leaky supply hose, then you will wind up having to buy it again for the new compressor or hose since those fittings are not re-useable. so you will spend 70 on two kits.

The stock compressor doesn't move the new r134a freon enough. to do it right you will need to replace the compressor ($$), which will require new brackets ($$) to mount the new ac compressor, and a new drier ($) because any time the system is opened to air the drier becomes ineffective

  AC work requires a vacuum pump that you can rent at autozone for free, as well as the manifold gauge set as well.  You will need both to do ac work. 

The leak test using freon will cost you in uv dye freon and multiple cans of it if you have a leak, uv dye kit pen and glasses, and r134 adapters.  and you may have more than one leak, so if you fix one leaky part like the ac compressor, and then refill it again with freon, again its costing you in freon at 12 bucks a can and you will use 3 cans each time.  and thats if you are using the newer r134.  It will cost you hundreds in freon if you get r12 cans.  and each time you do this  you have to rent the vacuum pump and gauges again to test for leaks or install freon.

I tried the leak test, found a leak at the compressor, replaced the compressor, had to get another r134 kit since you can't reuse the adapters with the rubber o rings,  it held a charge for a few days, and then another leak somewhere else but couldn't find it. replaced the hoses, repeat the procedure again, more money in freon, yada yada yada,  leaked out in a few days.... ($$$$)

i could see troubleshooting a leak if the car was a few years old, etc.  but at this point, to me the way to go is to replace everything using all stock components and r12.  it will probably be cheaper in the long run and be cooler

any time the sytem is "opened" and air enters the system including the hoses and drier, they have to be vacuumed dry where it boils all oils out of the hoses.  and supposedly if the drier is opened to air, its no good and has to be replaced again... so why take a chance replacing one part, like the compressor, and then you will have to replace the drier each time....keep adding freon..

oh and if you upgrade to r134 all the black o rings on the connections at the condensor/compressor, condensor/evaporator and evaporator/compressor will need the green o rings coated in special oil.  and you need to get the special tools that unhook these ac hoses to get to these o rings. 

Oil.  also there is special oil that is supposed to be added at the same time the freon is installed.  some freon actually has the oil in it but it costs more.  theres pag oil and esther oil.  Some oil is for r12 and other oil is for r134a, and some oil will work with both. 

new compressor
new condensor
new hoses (3)
new drier
new evaporator

if you know nothing about ac... i would take it to a shop, or be prepared to learn about it. 

 

MustangSteve wrote:

I think I would just find where it is leaking and go from there...  Pretty simple to do with a leak detector and a can of freon.

See my article on changing a Fox heater core on www.mustangsteve.com 

What kind of leak detector do you like?
 

I keep forgetting those "late model" Fox Mustangs are all over 20 years old.  Heck, I can still remember when the dad-gum 71-73 Mustangs were "late models".

My last experience with a Fox was my 1990 convertible and that was many years ago, so I defer to those with more recent experience on those cars.