14 F550 AMBULANCE HVAC ISSUE

[RyanG]

Have an ac issue and have no clue whats wrong. Customer say blows cool air in cab, the ac up fit is

tied into the factory system. It has a block between the expansion valve and lines with additional lines

coming out of the block to go to the rear unit. It has a roof mounted condenser and fan assembly but it

also looks like they looped the rear system into the factory condenser as well. If I turn on the cab

ac I only get 60 degrees out of the vent, but if I turn on the rear up fitted unit it will bring the front unit

down to 48 degrees. I checked the evap temp pid and don't see anything way out of range. the gauges

with the cab ac on are 10-12 psi low side and 145 high side. To me that would indicate low charge or

weak compressor. I evacuated system and it is full, threw a compressor in, txv valve and new dryer

cartridge and still have same problem. I know that the front will cool down if the rear unit is on because

the rear unit has its own electric compressor and the pressures will come up to where they should sit. Even

though the temp will go down to 48 with the rear unit on, it should still be colder than that on an 80 degree

day with minor humidity.

[lmorris]

The low side reading seems low while the high side seems normal/low. The course material I have from Ford School suggests A/C suction line partially restricted or plugged. What is the compressor cycle time?

[RyanG]

I just spoke with company who installed system and they think it was installed incorrectly. Its on its way over to them, I'll keep you

posted.