QuestionHoward,
The control drum in my HVAC system gears jammed and were chewed up, so back in the colder months, I removed them, and set the drum to a position that always supplied heat. With a digital thermometer in the dash vent, I am reading 135-140 degrees with the heat on. I saw no harm in tinkering a bit tonight, so I applied vacuum to the heater valve to close it, and with the compressor running, read about 68 degrees at the vent. This was cooler than the ambient, 73 degrees in my shop, but by no means enough to cool the cabin on the warmer days coming up. I have charged the system with what is available to me - 134a, but this seems pretty weak, still. I know you have said before the compressor is not so great, etc..., but is there more to it than the quality of compressor and refrigerant? I am trying to sort things out before I pay $250-300 for a new control drum. Am I wasting my time without the drum, or should I still be getting cooler air than this?
I know you prefer not to get in to HVAC questions, but I'm really only asking for your opinion on the questions posed, and I appreciate anything you have to say.
Thanks!
Michael
AnswerHi Michael,
You are brave setting the drum to get it cool or warm and not a bad idea but a lot of work. There are a few things you need to be aware of and one is that the Jag AC/heating system normally runs the AC all the time even when heat is on full. The control of heat and cool is totally controlled by vacuum door blending as jag calls it. That does not mean you can't just set the drum and get either heat or cool.
However, you will NOT get much cool out of 134 as it is a very poor coolant and requires a very high pressure compressor (that Harrison compressor can not get 134 to cool worth a flip) If you can't get R-12 (a medium good coolant) use one of the propane based coolants like Duracool or one of the other brands.
R-12 cools much better than 134 and the propane based coolants cool much better then R-12. After evacuation it takes about 3 cans of R-12 to fill and get good cooling in a Series III Jag and by using the propane based coolant I found that after evacuation I can't get more then one and a half cans of the propane based coolant before it is freezing you out of the car on a hot day.
Even in a 134 car (all late model cars) if you start it up on a hot day, you have to drive a city block or so before it even starts to cool. An older R-12 car will start cooling in half a block or less. A R-12 car with the Propane based coolant in it will be cold before you can get it into gear.
The only reason 134 systems replaced R-12 systems is because the Dupont's patent ran out for R-12. R-12 when burned turns into the poison gas used in WW1 but 134 is poisonous as is. R-12 may be a a danger to the O-zone but 134 is dangerous to anyone around it and is odorless. many people are afraid of the propane based gas because of the stigma of fire but it does have a fire retardant in it. but at least you can smell it if it leaks in the car. That's my two cents on the subject.
Howard
Howard
