CARRIER SUPRA 744 high suction pressure

[atetruckrepair]

hi guy's i'm a newbie got a carrier supra 744 thats has service fault thought it needed a charge but turns out possible blockage? pulling straight vacuum any common problems someone may know about before i dive in and start looking to see if it's a blocked dryer or bad exspansoin valve etc.any help would be greatly appreciated Thank's Bill

[cadwaladr]

Sounds like the valve set it on a temperature higher than the box temperature so it runs in heat mode if it doesn't vacuum. change the valve and the drier.

[atetruckrepair]

[QUOTE=cadwaladr;300850]Sounds like the valve set it on a temperature higher than the box temperature so it runs in heat mode if it doesn't vacuum. change the valve and the drier.[/Q

maybe i didn't explain it correctly when the unit is running it will not cool at all and with a guage set on the low side goes to straight vacuum and the high side goes high didn't know if there was a common problem like a valve that happens with this situation i'm thinking the exspasion valve may be blocked

[Shawn Carvin]

Does defrost valve are working?
maybe the valve not close?

[IRMechanik]

If you're confident the ***** charge is ok I'd look at either the expansion valve or the CPR. A blocked drier is possible but not likely. If you have a restriction and not a complete blockage you should see frost at the point of restriction. There should be a schrader port in the evaporator on the suction line, check your pressure there, this should tell you if the restriction is before or after the CPR.
If you have abnormally high discharge and low suction you may have multiple problems, either overcharged or non-condensibles in the system. If you have air/moisture in the system it will run high discharge and suction will be ok for a short time till the water freezes in the expansion valve and blocks it. Excessive moisture will not block a drier, a drier will collect as much moisture as it can till it's saturated then the rest will pass right through. Only dirt/debris will block a drier.

[atetruckrepair]

If you're confident the ***** charge is ok I'd look at either the expansion valve or the CPR. A blocked drier is possible but not likely. If you have a restriction and not a complete blockage you should see frost at the point of restriction. There should be a schrader port in the evaporator on the suction line, check your pressure there, this should tell you if the restriction is before or after the CPR.
If you have abnormally high discharge and low suction you may have multiple problems, either overcharged or non-condensibles in the system. If you have air/moisture in the system it will run high discharge and suction will be ok for a short time till the water freezes in the expansion valve and blocks it. Excessive moisture will not block a drier, a drier will collect as much moisture as it can till it's saturated then the rest will pass right through. Only dirt/debris will block a drier.

sounds pretty good what i find now is there is pressure to the exspansion valve and to the small equalizer line but nothiing passing through the valve i'm in the process of removing it now also i did have pressure at the test port at the evaporator thank's for your good input to my problem it's appreciated

[moggy66]

sounds pretty good what i find now is there is pressure to the exspansion valve and to the small equalizer line but nothiing passing through the valve i'm in the process of removing it now also i did have pressure at the test port at the evaporator thank's for your good input to my problem it's appreciated

If you have pressure at the test point in the evap is this with the unit running or does it go into a vac? if it goes into a vac then TXV if it stays at positive pressure and suction pressure at Compressor goes into a vac then CPR failure

[atetruckrepair]

I did not run it when i checked for pressure at the evap test port i will check cpr now thx, bill