AC blockage

Truck originally had decent AC.
then only half the front vents would blow cold.
now no change in temperature.

hooked up manifold gauges, close to zero charge left in the sys.
got the system evacuated.


heres where it gets interesting:

i starting pulling vacuum on low side, the pressure goes down, but the high side does not go into vacuum at all unless the high side valve is opened on the manifold gauge.
the latter causes the vacuum pump to change noise as it sucks the ambient pressure down from the high side.
if I understand correctly, the high side should already have some negative pressure just by vacuuming low side.


After one hour of vacuuming the system, pulling vacuum from both high and low side charge ports, we attempt to. charge the system from low side port.

low side pressure goes up, high side does not change.


pressure equalizes and we cant get any more refrigerant out of the can, which is still >75% full.

only way to get freon pressure to the high side is by charging to high side port.

so got about 40-60 PSI on both gauges, freon can is open to the low side system and no freon is being sucked in

we attempt to turn the ac on with the switch in the cabin, that doesnt kick the compressor on.


we jump the ac compressor relay, forcing the compressor clutch to activate, high side pressure starts to rise and NO PRESSURE CHANGE from the low side.

this further contributes to my theory that we have a blockage.

where is it though?

any tips on where i should start looking?

thanks

 

Def blocked. I'm not familiar with my Tacoma system but am relatively sure its an expansion valve system. Most common place to plug

 

Expansion valve would be my starting point.

 

Sounds to me like you didn't have your connections on your gauges screwed down far enough so that they open the valves on the service ports.

I've seen restrictions but I've never seen a 100% blockage in an A/C system, typically you will see a very low low side pressure and depending on the location of the restriction and service port the high side may be near normal or extremely high.

 

I don't believe this is the case for 2 reasons. First, we checked all the fittings and the and everything is good.
Second, when we force the compressor on by jumping the relay pins, we observe pressure increase on high side gauge, and no pressure change on low side gauge.
We see pressure increase on the low side when charging from low side port.
I believe this confirms the gauges are working

I understand you can change the expansion valve without ripping the dash apart by accessing it through the engine bay.
Denso unit is $25.
I plan on taking the system apart, and identifying the affecting component to avoid parts cannoning.
I would assume blowing compressed air through the fitting would be a good way to tell if we have a blockage or not.

 

I've changed out alot of Ford expansion valves and a few other brands. They all were farly easy to pull from a disconected line. I would imagine Toyota is no different.

 

See this thread Post # 6. It has pictures of how to get at the expansion valve and in line filters.

https://www.tacomaworld.com/threads/ac-compressor.796628/