Hello. I have a 2000 2wd 2door 4.3 blazer. My a/c line that comes out of the compressor blew both crimps apart.... Enough to let freon and the oil out. Anyhoo got that line replaced, new evaporator, and low pressure switch that screws onto that. System had vaccum pulled and charged back up but the clutch stays engaged when I select the a/c in the cab. It stays engaged the whole time when a/c is selected ..... No cycling what so ever. Thinking maybe the high pressure switch on the back of compressor or possibly a blockage of some sort. The air worked perfect before the line gave out. Almost like it built to much pressure and the lines couldn't handle it. When the air is on one line gets ice cold the other gets pretty darn warm. I don't want to just throw parts at it because there pretty pricey. Anyway if anyone could shed some light on this I would greatly appreciate it. Thank you.

 

The high pressure switch on the rear of the compressor is normally closed allowing the compressor to turn on. If/when high side pressure is excessive, (~400psi) the switch opens and shuts off the compressor.... the switch is not causing what you're describing, save your money

If you'e getting cold air from the registers when you first turn it on, and then the air warms up, or stops blowing, there are a few possibilites:
1) overcharged with refrigerant, possibly due to insufficient evacuation.
2) too much oil in the system
3) Engine cooling system not performing well, (overheating)
4) Condenser fins bent/damaged or restricted with debris
5) Radiator fins bent/damaged or restricted with debris
6) Fan clutch not working properly
7) Restricted condensate drain

If you're not getting cold air, or not cold enough, the orifice tube might be restricted.

You mentioned that you "replaced the evaporator and the low pressure switch that screws onto that". There are no switches on the evaporator. The accumulator, (aluminum can with 2 lines connected to it), has a switch. The switch that screws into the accumulator is the clutch cycling switch. It turns on the compressor when low side pressure is above 42psi, and turns it off when low side pressure is 22psi (or below). If low side pressure does not drop to 22psi when the compressor is running, the compressor will remain on. Any one or more of the things mentioned above can cause that to happen.

EDIT: If you run your hand along the high side line, starting at the compressor, follow it to the condenser, and from the condenser to the orifice tube, (in the line under the accumulator). The entire line should be warm/hot right up to the orifice tube, then turn cold. It should be cold as it exits the evaporator and enters the accumulator, and all the way back to the compressor. Post your results.

 

i would first unplug the clutch and see if it may be jamed on

 

LOL, now there's a thought

 

Sorry about that Hook....yes the accumulator 😋 The shop I went to just used the machine to pull the vaccum and recharge it. They did not use any gauges that I could see. I'm sure if I had someone who used the gauges they could pin point either the high side or the low side was the problem. We did find a leak at the nipple on the low side port. Tightened that so no more leaks. All the fins on condenser are good and straight took the grill out and checked. Probably wont really be able to know what's going on till I can find out how high or low each line is. And the clutch doesn't stay on all the time only when A/c is selected in cab and it won't cycle , it just stays engaged. I'm sorry but I am limited on my A/C tools for I don't really have any to check pressure readings. Anything else I could check before I take it back to the shop? Thank you for your help do far 😁

 

Without a manifold gauge set, you're limited on what you can check. You can try items 3, 5, 6 & 7 and check the lines as described in the "EDIT" at the bottom of post #2.

 

Where could you get a "descent" set of gauges at? 3,5 and 6 are good. I will post back tomorrow about the "edit". Gauge set would give me an idea of where to look next I assume. Again thank you HOOK! You da man! 👍😁

 

A/C is the removal of heat, not the addition of cold. Refrigerant carries the heat to the condenser where the heat is released. This is why the cooling system, especially the radiator and fan clutch are so important. If the heat can't be released, pressure begins to build in the refrigerant system. When the pressure builds in a CCOT, (clutch cycling orifice tube) system, low side pressure will not drop low enough for the cycling switch to turn off the compressor, can you say "catch 22"? As pressure continues to build it causes the evaporator to flood with refrigerant and ice up, which causes it to blow warm air, and eventually no air flow at all through the evaporator. It also causes high side pressure to go through the roof until something blows, hopefully the high cut out switch Too much oil has the same basic affect: The refrigerant can't carry the heat away fast enough. Basically, the oil takes up too much space, "cramps the style" of the refrigerant and exhibits the symptoms of a refrigerant overcharge, (which is what you've got going on).

With this in mind, a manifold gauge set will tell us what the pressures are doing and might help with diagnosis. We already know the pressures are too high, but how high are they? The sets are available at most auto parts stores, walmart, sears Amazon, etc. They start around $100 and go up to whatever you want to spend. You're basically paying for accuracy and the quality of parts used when manufacturing the set. For a weekend DIYer, plan on spending $150 on a guage set and another $250 on an evacuator pump... When it comes to AC equipment, cheap doesn't cut it

 

Cheap never cuts it man! Hahahah.... I've never delt really with an ac system... Well diagnosing one anyway. Does it help you any when I say the air coming out of the vents is cold.... It's like nothing is wrong except the clutch stays engaged the whole time the ac is selected. Hmmmmmm.... Anyhow I will try and pick up a gauge set this weekend and see if I can post results with that. 😁 I do know that the line that goes from the compressor to the "accumalator" ( hahahahahaha) is cold and the other is warm just haven't felt the bottom one as you described in post #2. I will post those results after work tomorrow for you. Thank you again Hook.

 

Pay close attention to the high side line from the condenser to the evaporator, (the one that runs under the accumulator). You'll see/feel dimples on the aluminum evaporator inlet tube, just rearward of the fitting on the evaporator inlet tube. The dimples hold the orifice tube in place inside the line. Forward of the connection, the line should be warm/hot. Rearward of the dimples, the evaporator inlet tube should be cold, and possibly have condensation on it, but not frosted. Let me know what you find.