altitude MAKES A DIFFERANCE its not rocket sience ,,, i done system by purging with freon never pulling vacumn
Back at it again to replace the expansion valve - a new 4-Seasons from Amazon. I checked first and the A/C system was still under pressure from last year - a good sign that the system was leak tight. Unfortunately the new expansion valve did not want to connect correctly to the line to the evaporator. Those are straight threads with an O-ring seal but it was impossible to snug up the fitting. With that of course the system will not hold a vacuum. So now waiting for another expansion valve.
The threads are not made well on the expansion valve. I measured and it is a straight 3/4-16 thread. I will chase those threads and try again.
Ok I removed the expansion valve again, ran a 3/4-16 die to clean up the threads, reassembled and by gosh the A/C system held a vacuum! So tonight I went out, now cooler, and recharged the A/C system and by gawd it cools! Only took two years and a pile of Ranchero bucks but it is cooling. I don't know how well yet but will drive to another car show come Saturday and will find out.
I drove the 15 miles over and back from the Saturday morning car show. Up in the 90's F on the way home so tried the A/C. The air is cold, just not much of it. However a nice cold blast when decelerating. I'm guessing that with the engine modifications there is no longer enough vacuum to fully operate the A/C vacuum motors. I will check for vacuum leaks first. If I need to add a vacuum pump, I will only need a pump for the cab vacuum controls since I've added hydroboost brakes. I see vacuum pumps running from $80 on up into the $400. Any recommendations?
If the controls have little or no vacuum, the air would come out the defrost vent. With the a/c on that air should be cold?
A vacuum reservoir should be more than enough - you'd have to have a BIG cam to kill that much vacuum, I'd guess there's a leak somewhere. Or it's plumbed wrong. Put a vacuum gauge on it (manifold) and go for a drive - just tape the gauge to the windshield.
Ok got the necessary fittings to connect my big A/C vacuum pump and gauge to replace the engine intake as the vacuum source. So the vacuum reservoir, transmission vacuum modulator, and cab are connected to the vacuum pump. I now have hydroboost brakes so no vacuum brake booster. With the cab selector in the off position, the system will pump down to 23 mm of Hg and hold that with the vacuum pump isolated. However, once the cab selector is turned to A/C, the gauge vacuum quickly falls to zero. So where is the leak? A bad selector switch, bad vacuum motor, or something else? I need to repeat this test moving the selector first to vent, then A/C, then heater, and defroster. That ought to tell me more.
Ooooh. I'll have to call 911 to get my body back out from under the dash. I did replace one bad vacuum motor years back with one from Hillbilly's pasture car supply.
I reran the cab A/C vacuum test again. Turns out to be a vacuum leak with the selector turned to A/C, heater, hilo, or defrost. No leak in the off or vent positions. It would be nice to know the vacuum switch to vacuum motor logic before I crawl under the dash and remove that front A/C and heater panel. I must read the manual just in case this is in there.
Ok, crawled under the dash and removed the plenum cover (and got back out). The one vacuum motor that will not hold a vacuum is a 18A318A according to the diagram above. I see these on ebucks with all manner of prefixes to the 18A318A and prices from a few bucks to over a $100. Amazon indicates a Standard Motor Products vacuum control VC221. I have not idea if this is the correct one. Any idea of where to find this particular vacuum motor?
Clark it pretty straight forward. It's the main AC /heat/ vacuum motor I have Extra of the that let me know if I can help you with that... Andy
Thanks Andy for the offer. I have a vacuum motor coming from ebucks. It's not quite the same but I can modify the arm with mine. The motors are the same.
