This is a bit of a scramble, I fit a 79 system on my 75, there are a few differences in the liquid line where it goes through the core support, I found Pick a Part trucks with the little valve that's right at the core support facing either direction, Help Number Dummy, please dig out one of the Bob fiche and see if it gives a decent image of the little brass valve that goes between the liquid line and the hard line from the drier, its on the engine side of the core support right at the grommet.

I could figure it out with a decent picture or two if anybody has a 79 factory air truck, a pic of the valve and I would like to see a pic of the expansion valve as well.

My system is a odd one, it uses the GM A6 A/C compressor with the Saginaw power steering pump, it is a factory Ford setup, (the evap unit was on the roof of the cab) but the lines were gone when I got the truck, (if anybody has a image of this setup or if ND you have a fiche of it, that may really help) I fit it with the standard lines from a 79, it seemed good, but it makes a noise when temps get to 100-105F like the valve is vibrating and the low and high side pressures drop, blows warm, otherwise when its quiet it will blow 40* out of the dash, it may also be the expansion valve, it's new....but China new, the system is R12 so it kills me to loose freon hunting a problem.

Thanks in advance from a daily driver in 100+ temps.

 

This is the expansion valve I used for my 73 with factory ac. Looks almost identical to my old one. My brother in law, a diesel mechanic, says it is also the same exact one used on Peterbilt and Kenworth trucks.


Four Seasons 38901 Expansion Valve

 

I have the later valve, that's the 73-75 valve, I have the 75-79 valve, but thanks for the info.

 

D5TZ-19849-A .. Expansion Valve - Use with factory installed integral A/C (Motorcraft YG-163) / Obsolete

1975 F100/350 from serial number W00,001; 1976/79 F100/350; 1978/79 Bronco.

Your system is not an odd one, it's an incorrect one.

Saginaw P/S pumps were not installed on F100/350's. Only 1972/79 Passenger Cars with Hydro Boost and 1975 and later Econolines.

The GM "Swash Plate" compressor was only installed on 1972/76 Thunderbird & 1972/78 Lincoln/Continental Mark 460's.

A/C evaporators mounted on the roof were installed on BIG trucks. No F100/350 ever came with one.

btw: Around noon it was 74 in Malibu, an hour later it was 90 in Camarillo and when I got home around 3, it was 104.

 

OK you have good ac but a hodge podge of parts.... that are not conducive to any system. Now, those gm a6 pumps are... well a typical gm product, lets you down when you need it and works great the rest of the time. I have done several farm and ag machinery systems utilizing those, they were generally a problematic unit at best compared to yorks and sandens. It might take some time with guages to properly troubleshoot this. maybe an expansion device maybe a compressor, maybe an old evaporator core that isn't quite right... Good luck.

 

I should have mentioned it came off a roll-a-long conversion, they took out a 390 4 speed and put in a 460 auto, added the air and proceeded to make a crewcab cowboy Cadillac.

I have the A6 aluminum new replacement compressor, it will blow 40* out the dash until the outside temps reach over 100* then the noise will start (like a horn sound) and it stops blowing cold, the high and low pressures drop to nothing, but like I said in the post it's the small brass valve at the core support I'm in question about, right by the sight glass, that fitting is a one way valve of sorts.

It's got new compressor, expansion valve, drier, all hoses, evap core and condenser have been cleaned and pressure tested, works fantastic ........until it doesn't.

If anybody has the ambition to snap a pic of the small valve at the core support, I would very thankful. I'm pretty sure it's right, just need to verify.

Thanks for all the info so far!!