1985 300D expansion valve question
 

I took my 300D to my a/c tech and he determined that the expansion valve is "swinging". I received the new valve from fastlane today and will take the car to the tech next week to get it put in. My question is - all I see on the expansion valve is a little capillary tube right on the end of the "block" of the valve. What in the world controls how much the valve is open, etc. Looking at this it is just the ambient air in the cockpit. Most exp valves that I have seen in the past have a capillary tube that ties back into the evaporator area and then controls the valve. Why is it that the one on the 300D is this way?
thanks

The needle that goes through the center of the valve opens and closes according to the temperature of the gasses flowing through it. The tube at the top is so they can fill it under pressure.

I replaced the expansion valve this morning after getting my a/c tech to remove the 134a. I took it back to him and he has started the charge process. When I stopped by a little while ago he said they may have put too much in it - it was not blowing very cold.

I am wondering if maybe something else is wrong with the a/c system. What are the different ways an evaportor can fail? How bout the dryer? Could either of them failing prevent me from getting cold air. I am really trying to get it below 65 dF with 90 dF ambient conditions. If the pressures are within spec what else could cause it to not cool other than it being a 300D that has been converted?

I need to know about how much r134 it should take. I am under the impression that if you use the conversion of .80 to R12 then it is not right. I had a rep from VintageAir tell me to have them put a pound in to pick up the pressure switch and then add an ounce at a time till it cools it down.

Picked the car up from the a/c shop and the tech said it still has a slight leak somewhere. Isn't there some type of ultrasonic device that you can use to "sniff" out those leaks? Is it something a diyer can afford. I may try to get someone with one of those sniffers to try to find the leak for me. I suspect a couple hoses.
I will keep everyone posted. Oh yea, it is blowing out 53 dF air now.

The best way I've found to locate a leak is to use flourescent dye. I bought a kit with the fluorescent light, some uv enhancing/eye protection glasses, and dye removal spray for about $100 from OnTool. Do a search of OnTool to find their site. You can find the r134 UV dye at any decent auto parts store that caters to the garage trade, not at the chains like autozone.

I had fretted over my 240D until I used the UV dye and homed in on the leak immediately after putting in the dye.

I put dye in my Vette and found the leak immediately, it turned out to be a $10 pressure cycling switch.

To take this approach, you need to be equipped with regular a/c service equipment such as a set of guages at a minimum, and preferrably a vacuum pump to do all your own a/c service.

Best of luck with it,

Thanks Larry
I ran it some this morning and was getting 53 dF air out of it which is pretty good. I was told that if the evap is leaking you will see the dye mixed in with the condensate coming from the a/c system drain. I will watch how it performs over the next week or so.

I found I had not tightened up one of the fittings on the expansion valve enough. It is now blowing 53 dF air when the outside air is 91 (really pretty pleasant for this part of the country in August). Another question - the site glass in the dryer is not clearing up although it is blowing 53dF air. Should the site glass be clear?

Has this system been converted to r134? If so, you should ignore the sight glass.

If the system is still R12, you should add enough refrigerant to clear the sight glass.

Good luck,

It has been converted Larry. I will take it by the a/c independent today and have him put that ultrasonic "sniffer" on it to try to determine if I have resolved all the leak issues.