Class A AC woes - bad expansion valve??

[rgnprof]

I have been redoing my 2015 Fleetwood Class A (Ford F53). Lost all my 134a over the winter - found a leaking hose, replaced, nitrogen pressure tested (no leaks), evacuated down to 30, held with no leaks. This systems seems to be a hodgepodge - Ford chassis components (Sanden compressor, Ford drier, condenser, assuming the evap is as well, but there is an Evans Tempcon (no longer in business) sticker on the evap case, but with nothing indicating refrigerant capacity - left blank.

Went to recharge (weighing it in) and have found conflicting information on 134a capacities - Evans catalog (online) says 2.13 lbs and the 2015 Ford F53 chassis manual says 2.5 lbs. I put 34-35ozs. Vent temps started at just over 100F (it's about 94 here), full charge in and vent temps are right at 70F. Hi side is 275psi and low side is 34 psi. Sprayed the condenser down and pressures dropped - low side down to 25 and hi to 150 psi. After a bit, the hi got back up above 250 but lo stayed in the 20s. Vent temps may have dropped a couple of degrees.

One other thing - I don't think I ever heard the compressor cycle off.

Any suggestions? I was thinking a bad expansion valve??
If my system does really take 40 ozs instead of the 35 I put in - would that make much of a difference?

Thanks!
ryan

[tbirdtbird]

First if it is an Evans evap I would say the online value is the way to go. The charge can be adjusted later if need to be.
Next what does ‘evacuated down to 30 mean?’
Vacuum is expressed in terms of microns.
Are you using a motor driven evac pump or one of those Horrible Fright vacuum driven ‘pumps’
Pressures s/b at 1800 rpm.
Are you certain no air has been introduced

[rgnprof]

Yes - 30 microns. I'm using a pretty decent vacuum pump. Vacuumed for 45-60 minutes - let it sit for a while and it held. Pretty sure no air- I made sure to purge each time I connected a new can. But, I'm not positive...

At 1800-2000 rpm - hi side goes to 300-325 and low side drops to low 20s.

I have no idea about the evaporator (manufacturer) - but I did find an expansion valve part number - egelhof TBG 2D No.320500S.

[Cusser]

Lost all my 134a over the winter

You did replace the accumulator/drier, right?

[JohnHere]

I have been redoing my 2015 Fleetwood Class A (Ford F53). Lost all my 134a over the winter - found a leaking hose, replaced, nitrogen pressure tested (no leaks), evacuated down to 30, held with no leaks.

Great! A 30-micron evacuation is fantastic—or did you mean 30 inches of mercury (inHg) indicated on the low-side gauge of your Manifold Gauge Set? Above, you mentioned 30 microns.

Went to recharge (weighing it in) and have found conflicting information on 134a capacities - Evans catalog (online) says 2.13 lbs and the 2015 Ford F53 chassis manual says 2.5 lbs. I put 34-35ozs. Vent temps started at just over 100F (it's about 94 here), full charge in and vent temps are right at 70F. Hi side is 275psi and low side is 34 psi. Sprayed the condenser down and pressures dropped - low side down to 25 and hi to 150 psi. After a bit, the hi got back up above 250 but lo stayed in the 20s. Vent temps may have dropped a couple of degrees.
One other thing - I don't think I ever heard the compressor cycle off.

Based on your description, I think it might still be undercharged. Did the center vent temperature drop when you sprayed the condenser?

As for the high-side pressure being elevated, that could be due to a condensing problem. Presuming you have electric fans, do they come on as soon as the HS pressure exceeds ~250 PSI? If not, that's something to investigate.

Are there any gaps between the condenser and radiator? If so, sealing them will also improve condensing.

[rgnprof]

Yes - I did replace the drier.

And yes -I did mean 30 in hg using the low side of my manifold gauge (typing in a hurry). I do have a micron gauge but I didn't use it here.

I don't see any electric fans - anywhere. When I sprayed the condenser, the vent temps dropped a few degrees - not significantly.

[JohnHere]

In your motor home, is the engine mounted front-to-back (longitudinally) or side-to-side (transversely)? If it's mounted longitudinally, does it have a fan on the front of the engine and a viscous-drive clutch? If so, the clutch might be shot, which would explain the high HS pressures.

[bohica2xo]

John:

I can answer part of that question for you. The F53 in that model year has the 6.8L V10 engine mounted conventionally with a viscous drive fan clutch. Truck chassis.

The fan is 19.6" diameter with 8 huge blades. When the clutch is working I can hear one for blocks. That kind of torque load can be hard on a clutch.

For the OP:
testing should be done at 1800+ rpm. Cabin fan on highest speed. Run for at least 90 seconds to stabilize, and record pressures and temperatures while the engine is above 1800 rpm

[rgnprof]

Yes, I see the big 8 blade fan behind the radiator and yes, this is the 6.8L Triton V10. I have no electric fans.

Just checked pressures at 1800-2000 rpm - hi side 210 psi and lo side 14 psi. Maintained that for at least 90 seconds and didn't change much. At idle, high side 215 psi and lo side 27 psi. Temps in front of the condenser about 95F (humidity today about 40%) and vent temps at 60F.

[Tim]

All Data: Due to various configurations by aftermarket motorhome builders, the A/C system on the motorhome stripped chassis ships from the factory as a partially assembled system. Because of this, the system does not contain a refrigerant charge.

From the last comment. It looks undercharged to me.