weird ac question

[otter5555]

i installed a new underdash ac unit in my old chevy truck
bought it on ebay
it has the sanden compressor

for 2 months it worked perfectly, blew 22 degree air, cycled perfectly

then it started freezing up even with the thermostat turned to 0

i suspected low freon but pressures were perfect

i went ahead and removed the freon , pulled a vaccum and put the exact amount specified in again. same thing freeze up in 15 minutes

i bought a whole new evaparator and installed it. freeze up in 15 minutes

i bought a new compressor. same thing. freeze up in 15 minutes.

i pulled belt off of the compressor. freeze up in 15 minutes.

so, here we are. not even a belt on the compressor. 15 minutes driving down the road @ 45 mph and the evaperator is a solid chunk of ice.

i recently made an 8 hr trip and it stayed frozen the whole way.

any ideas?
thanks in advance

[Bandit130]

Welcome to the site.

[v30crewcab]

need to adjust your low pressure switch, or the expansion valve is hanging up and needs to be replaced.

[otter5555]

Originally Posted by v30crewcab

need to adjust your low pressure switch, or the expansion valve is hanging up and needs to be replaced.

replaced both already but thanks

every part of the system has been replaced 2x except the hoses

i dont even have a belt on the compressor and it freezes up

[v30crewcab]

I've had to adjust many low pressure switches right out of the box. do you have gauges you can hook up and read the low pressure side?
how could it possibly freeze up with no belt on it? no spinning no pressure??????

[otter5555]

Originally Posted by v30crewcab

I've had to adjust many low pressure switches right out of the box. do you have gauges you can hook up and read the low pressure side?
how could it possibly freeze up with no belt on it? no spinning no pressure??????

that's my whole point. the compressor has no belt on it. i took it off . the compressor is not turning at all.

in 15 minutes driving 45 mph it freezes solid and stays frozen till you kill the engine

[70GMCer]

Freezing without the compressor connected ?? IMPOSSIBLE !!!

Freon is a gas within the system until it is compressed to a liquid.

If you are getting ice, then it is because you either have a blockage within the system, dirty evap or condenser. But, again, no icing without the compressor running...

When the system is iced up, the low pressure reading with be very low on the gauge.

I'm just wondering if this poster is just seeing what comments will be made on this subject. Wanting a laugh....just saying....

[otter5555]

Originally Posted by 70GMCer

Freezing without the compressor connected ?? IMPOSSIBLE !!!

Freon is a gas within the system until it is compressed to a liquid.

If you are getting ice, then it is because you either have a blockage within the system, dirty evap or condenser. But, again, no icing without the compressor running...

When the system is iced up, the low pressure reading with be very low on the gauge.

I'm just wondering if this poster is just seeing what comments will be made on this subject. Wanting a laugh....just saying....

not hardly. this has been going on since oct 2017. i've tried everything. what is happening can't happen....but it is.

[Wgesnerjr]

Seeing is believing.

Got pictures?

[truckin 79]

If vents are shooting out 22 degree temps that is a freezer unit not a AC unit. Take it to a AC place, I have found places that charge as low as 66 plus whatever freon they use.

[tucsonjwt]

x2 on take it to a pro. Make sure it is a shop that does only A/C, not jack of all trades mechanic.

I personally am skeptical of aftermarket A/C systems, but Sanden is highly recommended by the local A/C shop I use, so I don't think you have a compressor problem. When I finally get the compressor replaced on my old 83 I think I will go with an Alma Products new A6 because I don't like the cheap looking adapter brackets I would have to use to convert to Sanden.

[jkk]

No compressor running I say BS on the freezing up part.....!

[hatzie]

Basic Principles of Refrigeration
Liquids absorb heat when changed from liquid to gas

Gases give off heat when changed from gas to liquid.

For an air conditioning system to operate with economy, the refrigerant must be used repeatedly. For this reason, all air conditioners use the same cycle of compression, condensation, expansion, and evaporation in a closed circuit. The same refrigerant is used to move the heat from one area, to cool this area, and to expel this heat in another area.

The refrigerant comes into the compressor as a low-pressure gas, it is compressed and then moves out of the compressor as a high-pressure gas.
The gas then flows to the condenser. Here the gas condenses to a liquid, and gives off its heat to the outside air.
The liquid then moves to the expansion valve under high pressure. This valve restricts the flow of the fluid, and lowers its pressure as it leaves the expansion valve.
The low-pressure liquid then moves to the evaporator, where heat from the inside air is absorbed and changes it from a liquid to a gas.
As a hot low-pressure gas, the refrigerant moves to the compressor where the entire cycle is repeated.
Note that the four-part cycle is divided at the center into a high side and a low side This refers to the pressures of the refrigerant in each side of the system

TANSTAAFL... If the belt is off the compressor then there's no cooling at all.
The compressor has to compress the refrigerant or there's no refrigerant state change to liquid at the condenser and back to gas at the evaporator.
No state change = no cooling. End of story.

I assume the evaporator froze up and you expected the block of ice to thaw quickly when you pulled the belt. Nope. Ain't gonna happen. Once it's frozen solid there's no airflow through the evaporator. It could take several hours to thaw even on a good hot day.
Don't believe me? Set a 6" x 3" x 12" solid block of ice in the shade. You may be shocked how long it takes to thaw even on a relatively hot day. The evaporator box is mildly insulated. It could take a very long time to thaw out.

You are not getting 22°F out of the vents. 22°C (71°F) I can believe... 35°F vent temps are possible but too low as the evaporator will be below the frost temp of 32°F or 0°C. You want vent temps in the 40-45°F range with outdoor ambient of around 85°F... without driving the high side pressure into the stratosphere when the outdoor ambient temps climb into the 100°F area.

A freezing evaporator is either a low refrigerant charge or restricted airflow. Intake to the blower? Mice or leaves or...

[SunSoaked]

Well said hatzie.
Stick a fork in this thread!

[Jeepwm69]

I've got a 305 in mine. The A6 might keep it from going anywhere LOL.

I have Sandens on my AMC era Jeeps. That was the stock setup on the CJ's.