Hi guys, The airco on my 72 Centurion works fine, the airco lines under the hood are getting cold enough to create some ice. But before the big pipe goes into the big box which is mounted onto the firewall, something cuts it of and before it goes into the box it's just normal tempurature and no ice anymore... I can see it is shutted of at the last valve on the line before going into the box. On the 'valve' I can only see a steel line/wire goes down into something. I don't know nothing about airco and heating systems so please help me out. I can't post pictures yet because I need to have at least 10 posts on this forum.
I'll give you the basics of air conditioning and some things to check. The compressor squeezes the refrigerant and pumps it under pressure to that box on the firewall. Inside that box is the evaporator, it looks like a small aluminum radiator. A small opening inside the line lets a controlled amount of the refrigerant into the evaporator. When it expands it aborbs heat, making the evaporator cold. The car moves air through the evaporator and the air gets chilly. That chilled air should blow into the car. The refrigerant moves through more tubing to the condensor which is in front of the radiator. The heat is transmitted to the outside air and the refrigerant returns to the compressor. There's a series of safety devices that can shut down the A/C if something is wrong. If the compressor can't compress, if the pressure in the lines is below a threshold, if the air inside the box on the firewall dips below 35 degrees or so, then the A/C system will shut off. Problems with A/C fall into 3 broad categories. 1) Insufficient refrigerant caused by a leak. 2) Problems with the safety systems, or wiring. 3) Mechanical problems either with the compressor or in the air flow system under the dash. I think you have the 3rd category. You are seeing the lines get cold. That only happens if the A/C system is working. This means you have refrigerant, the compressor is working and the safety devices are not stopping it. So, why aren't you getting chilly? I see 3 possibilities to check: 1) The flapper doors in the heater box aren't working. These operate by vacuum hoses. The hoses can get brittle, or come loose, or the doors can sometimes get stuck. You should hear these doors opening and closing as you move the heater controls. If you don't hear them move start checking the vacuum lines. The vacuum comes from the engine and is connected to a little tank on the firewall. The tank has a series of vacuum hoses running off of it. Check all of these lines. Then check for vacuum at the heater box. If you get that far tell us what you find and we can direct you further. This is my bet. It's the most time consuming because you're tracing these little vacuum hoses under the dash. It's time consuming but usually cheap as the fix is a length of hose. 2) There's a valve that's supposed to shutoff the hot water when the A/C is on. It also runs off vacuum. Turn on the A/C and the heater hose should be warmer on the engine side than the side that runs to the firewall. If this valve isn't working the A/C cools the air and the heater warms it back up. Fixing problems in the vacuum system might start this valve working. 3) The system is working but not working strongly enough. This can be checked by testing the tempurature within that black box on the firewall. If it's getting cold in there the problem is elsewhere. It's really good news. Because the system is getting cold most of the really expensive items are working. Good Luck, John
Your best bet would be to take this in to a professional shop and have it diagnosed, without actually seeing what you have I am just jumping to conclusions here. However, you may try this: Using your fingers, you may try checking how cold both pipes are coming out from the airbox. (That is the evaporator) If one is signifigantly warmer than the other, then there may be a restriction at the expansion valve, sometimes that can be caused from ice buildup inside the valve at the orfice due to excessive moisture in the system. Otherwise, it could be low on charge or as stated above it could be a different problem. Without knowing the exact pressures your system has while in operation, it's just a guess what the problem could really be. :Smarty:
Hi! I checked some things this evening. I also made some pictures which i uploaded on photobucket. I checked the doors when I shuffled the heater controls ( I have got climate control). You can hear doors shutting and opening, for example the defr. for the windshield blows wind against the windshield and the auto function just blows trough the normal air vents. Also I noticed the wind blows harder when I lower the tempurature control to 65 and it blows softer when i put it to 85 degress fahrenheit. I also can hear a small 'puff' when I turn all controls 'off'. Then the two big and hot hoses. The red one (left from drivers position) is just the same tempurature as the other one, I can't notice any difference with the airco on. When I shutted down the engine I saw something weird. It looked like a small line from the big black box putted something hot into the airco line. I got a picture of that too. Looks like it's problem 2? For the pictues, check on photobucket my user's album: Michelhaak
Most likely your air conditioning system needs to have refrigerant, R-12 or equivalent, added. This is what the POA valve, the one in the picture, looks like when the system is low on refrigerant or if the POA valve is bad.
