diesel402004

Ok, we're in the 100s and it's ac season again (for a little while anyways). Only blowing 50 at the vent and the compressor's not cycling like it did last year (it stays on, system is still R12 original). No stuff blocking fins in condenser and evaporator and nothings changed since last year. Have shop in town that still has evap equipment and freon, but don't want to waste his time if it's something else.

samiam4

It's got a sight glass. You can visually check the charge. Service manual has instructions and the web is plentiful.

Only other factor is fan clutch. I assume you have good airflow and not the dreaded rats nest of debri in front of the evaporator coil??


Michael

diesel402004

Thanks samiam4. Where is the sight glass supposed to be? I dont see it on the evap can. Does someone have a pic?

Jim Lane

Make sure the hot water is shut off to the heater core, that can easly raise evaporator temps 20*-30* also check for low charge.

Montana2x2

It's on the receiver dryer mounted under hood passenger side on the fender lip near the front, looks like a small tank.

diesel402004

Thats what i assumed but I dont see any "sight glass" on it? Little tiny hole on inboard side but no "view" of bubbles or movement that I can discern??

Montana2x2

Sight glass is on the top. If it has been replaced there might be a piece of tape or plastic over it to mask it off from the paint. Take an awl of knife and lift out the masking, it is small about the size of a pencil eraser.

diesel402004

Got it. It was covered over with paint. Looks like it is showing a "normal or overcharged" condition by being clear. Thanks for the help as always.

D

Montana2x2

Watch it as the compressor cycles off and on a few times sometimes you will only see bubbles then if the charge is just a little low. Over charge will not run as cold as proper charge but if it was working good and you have not added R12 it should not be overcharged. Hooking up gauges is the best way to figure out a/c problems. Good luck.

sooty

back to samiam's fan comment, at idle you should feel heavy presence of air pushed behind fan.

maybe368

Remember that the pressures and temps produced by the ac are heavily related to atmospheric conditions. Hot, dry days are the best. If you have a clear sight glass, the compressor is spinning, you have not added any r-12 and it is producing 50 degrees on a 90 degree, humid day, it sounds like it's working pretty good. A 40 degree drop is excellent performance. I would do what Jim Lane said and shut off coolant flow to the heater core and see what happens...Mark

maybe368

Also, are you getting a lot of water out of the condensate drain? It could be clogged if not...Mark

j_martin

The measure of heat content in air is called enthalpy. As you can see in the chart, 32° C (90°F) at 100% RH has a heat content of 112. At 50% RH, it's 70. At 30% RH it's 58. Humidity makes a huge difference.

When we set up AC for large gatherings of people, it's sometimes better to throw away the air and replace it with chilled outside are, than to extract the heat and moisture(enthalpy) from the used air.

loudhornsrule

I replaced my whole system last year. I get 40 degrees at the vent on a 100+ day(highway), and 50-55 degrees- stop and go around town on 100+ day. I have 134 in there also. These trucks will cool if you get them right. My truck cab has a lot of air leaks, but on the highway it works better than my wife and daughters New Fords

thrashingcows

Ever since installing my PS Intercooler, and having the condenser behind the IC, my AC does not cool as efficiently as it should....but that is to be expected I guess.

Guess my project for next year will be to mount a remote condenser back under the bed of the truck with electric fan(s). Then I might get my cold AC back.