Could be airflow, and refrigerant charge. Too little airflow across the evap will cause the temperature to drop. Did you have the heater box apart when you did your car?
Oh, yes!! And, I hope to never take it out again. Everything was replaced or tested -- everything except the "anti-icing switch". Also had the cowl cover off for cowl repair and all the duct work out. Can't imagine any air flow restrictions. Charged the system with 2 16 oz cans of R134A as instructed by Classic Air.
That could be part of the issue, the factory charge is under 2 lbs (16oz/1lb) Depending on the hoses, and the condenser,gauge hoses, it's something that should be monitored while charging, you have to seen what its doing. It's not just dump it in and go, you have to fine tune it. What size Sanden did you use? the 5 cfm? I hate those cans of refrigerant, they should be illegal.
Hey guys, I don't see this as a thread hijack ... I am trying to learn as much as I can about these right now, and it is all educational. Thanks! Dave, You mentioned airflow ... do you think either design might be better in that respect.
Everett, If you never ran it on high ... ... when the A/C system was in good running shape after I first got this car (about 4 weeks at a time, 3Xs in the summer of 1993 ... spent $600 on the A/C that year ), it got run on high a lot. I have added a lot of sound deadener and insulation to the floor, and I am due for new door seals, so, I think that will help a lot.
Actually, that's pretty normal when you are using the lower fan speeds...not as much warm is flowing over the evaporator and it allows it to get colder and possibly freeze up, thus the switch kicks in. Now, on at least one of the Mavericks I've taken apart, the anti-icing switch was adjustable...so if yours is kicking in too early you might be able to adjust it so it switches the compressor off at a colder temperature. I'm using a 1981 Thunderbird system as the basis for the air in the Mav now and it uses a valve that senses pressure to keep the evaporator from freezing up, so I don't have an anti-icing switch anymore.
Didn't notice any adjustment on the sw when I had it out. BTW, the orifice (?) that sits on the high pressure line just outside the firewall looks like it also has a capillary tube to sense temp. Does that device open/close the orifice depending on temp?
OK. Since you don't think its a hi jack, here's the post back on this thread. Other thread deleted. OH CRAP!!! There I go again -- trustin' my memory. Classic Auto Air, who supplied the compressor (don't know what size), hoses, consenser, and cleaned and checked the evaporator, told me the system should get 24 oz. We put two 12 oz cans in it. It was blowing mid-30 degree air after about 16 or 20 oz. This was the second time we charged the system. The first time we quit when it was blowing mid-30 degree air but on a hotter day the discharged air was just cool so we evacuated it and put the recommended 24 oz back in. Works great now except on hot days the fan has to be on high or compressor cycles and air isn't real cold when the compressor is off. When the "anti-icing switches" go bad, do they typically stay open too long allowing the evaporator to warm up too much? Thanks for your help.
If you mean that brass block, that is the TXV (thermostatic expansion valve), and it does sense the temperature of the refrigerant going into the evaporator to control the flow. Technically this should be changed to one that is compatible with R-134 when you change to that refrigerant. I'm not exactly sure what happens if you don't, but it usually means the system won't work as well under all conditions...
Yes, the expansion block. Couldn't think of the right name. I replaced mine with new R12 version. Someone, can't remember if it was the Classic Auto Air guys or not, said it would be OK. Doing a lot of things for the first time ... Guess I'll just run the fan on high on hot days. Don't have to do that on the newer vehicles but that's OK. Just wondered if there was an easy way to improve the evaporator effectiveness since I don't think its doing all it can on the lower fan speeds. Thanks.
It doesn't sound like it's the evaporator, but the way you describe it the anti-ice switch is allowing the compressor to stay off too long before it kicks back in. Are you sure your switch isn't adjustable? As I recall on mine, the adjustments were two recessed small screws...one set the temperature at which the switch triggered, and the other one controlled the cut-in time, which is probably what you'd want to adjust...
Could be I didn't notice adjustment screws. IF it ever comes back out, which I hope it doesn't, I'll check it closer. Thanks. :Handshake
I don't recall seeing any screws on mine either. We're talking abt the little black box w/ the long probe that goes into the heater box between the evap fins - right? Im w/ u Jim - mine is working gud enough not to take all that stuff out agn unless, no other choice.
Guys, I just took a look at both units I have here ... they are adjustable. The early one has a plastic cover that would face the back of the dash. Pop that off, and there is a screw that holds down a curved copper plate that is stamped "COLD" with an arrow. The later one has two screws that are in a well in one side, located close to the electrical terminals. You really have to be looking hard for either of these. I will snap some pics of this when I get more time. Mark, you never cease to amaze ...
