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A/C issues

larrywlarrywMember
I've been riding around in Miss P now for the third season and since everything else in the car seems to be working OK now I thought it was time to look into the A/C system.

My system is still plumbed with the stock equipment, excepting the compressor which has been upgraded to a rotary type with R12 type connections on the back.

An opportunity to get some R12 refrigerant and oil presented itself. I'd been told that in a stock system R12 worked the best so I grabbed 3 12 oz cans of freon and a matching container of compressor oil.

I borrowed a vacuum pump and a set of R12 gauges from a mechanic friend. I set up the pump and started to draw down the system. Immediately I noticed a sucking noise coming from the receiver/dryer. I found it was coming from a hole in a fitting screwed into the r/d near the sight window. It looked almost like a carb jet.

I removed the fitting with the hole it it and replaced it with a solid set screw plug I found that fit perfectly. Now the system seems to hold a vacuum.

I got to thinking that after a couple of years of exposure to the atmosphere that the r/d was probably nfg. I called the mechanic friend who confirmed that it most likely was indeed junk.

After explaining the fitting with the hole in it to him he said tht it was actually a safety valve that had blown out most likely because of a plugged or otherwise compromised expansion valve.

Replacing the R/D looks like a cinch, and would most likely come with a new safety plug installed. Would anyone have any part #'s or suggestions on a bolt in replacement receiver/dryer?

On to the expansion valve. That doesn't look quite as easy. Whats that like to replace? Dashboard disassembly? My buddy said that R12/R134A compatible expansion valves are available and now would be a good time to put one for when ever I do decide to go to the R134A. Again, would anyone have any advice on part #'s for a compatible valve and the replacement work?

Someday I will go to a front mounted condensor and convert to 134A. But for the meantime I'd just like to replace the these two components and get the system operating.

All commentary appreciated, as always.

Thanks in advance.
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lf-tp2511lf-tp2511Member
Larry,

I'm using this r/d

http://tinyurl.com/55r4tm

This expansion valve should be correct, but I bought mine off eBay

http://tinyurl.com/5wa454

Replacement sticky tape -

http://tinyurl.com/54pvha

Valve CAN be removed with dash in place. First, take some Motrin for the pained, sprained back you are going to get.

Remove passenger seat and glove box. Remove old sticky cork tape. Free capillary tube from its friction clamp holding it in place on freon line, note position. Get your large open-end wrenches and undo fittings on both ends of valve. CAREFUL - do not twist soft, delicate copper pipe off of the evaporator. Tightness of area means many short throw wrench movements, and very difficult bracing, repositioning-flipping of wrenches. Not fun.

Fine mesh screen is within one end of the valve, remove with dental pick. This valve is known to clog, and that could be the reason your pop-off valve on the r/d blew. If screen is clogged, clean with solvent and air. The valve is likely still good - replace per your preference, but new one will probably not have screen. I reused mine.

R-134 is scheduled for phase out in Europe in about five years, and soon thereafter here in USA. So my thought is to just stay with R-12 as it is the best, and both will soon enter the 'obsolete, no longer made' category. eBay, in the Winter, is a fine place to buy the 12/14 ounce r-12 cans. I've got about 18 of them stashed.

New drier will not have safety valve. It will have two ports. You can add a high/low pressure switch and wire it into your system per article at Panteraplace.

Switches here -

http://tinyurl.com/53tlt5

New drier may have sight glass painted over - remove round piece of black-painted tape. Don't ask me how I know this.

PM me if you have other questions.

Larry
angelobangelobMember
I concur with previous info with one little addition.

I would check and make sure of the condenser and condenser fan area of the system. USUALLY, if the restriction is at the TXV the system cannot build up that high of pressure since it is not getting any refrigerant thru the evaporator, it will go into a pumpdown state. If the condenser stops doing its job or if the unit is overcharged or over reved, then it will blow out the safety plug or toast a compressor and/or hose.


Angelo
larrywlarrywMember
Another little something has come up.

My car is #7102, among last of the Ford era cars

Is anyone aware of A/C wiring changes at the "anti icing" switch area that may have been a late production change NOT reflected on the late "L" model wiring diagram?

I find an extra relay or something down there and my rotary dash switch only has two wires, a brown and a blue/black.

The white/black wire that's supposed to control the A/C comp. clutch terminates on this extra relay looking thing along with three others (a yellow, a dk blue, and a black).

All the unidentified wires go into a sheath and disappear behind the heater box. I cannot see where they go.
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