Anyone with a 1998 Allegro Bay on Chevy Chassis?

[Takereasy]

I'm looking for the R134 Charge Weight for the Dash Air on this MH.

Chevy P32 Chassis with ACME Evap/Heater box. There "should" be a label stuck to the evaporator case with the R134 Charge Weight however mine is so faded it can not be read.

I'm hoping I find someone that still has a label intact.

Tiffin said around 2 to 2-1/2 pounds. That isn't very specific for something that should be charged by weight.

Thanks,
Richard

[Gale_Hawkins]

From my experience many shops will add too much R-134a in many auto applications. I did it with our older P30 an experienced the noise and confusion of the PSI safety valve releasing. I was not there but the same thing happened to the Escalade early this summer after the AC was topped of last winter. The son thought a radiator hose had blown because he found some green liquid under the SUV but that was UV dye because that is the only vehicle we own that does not have green coolant in it. 🙂 The thing that clued me into figuring out it had been over charged was the fact they reported (I was at the office) it still cooled some so I knew it had some R-134a left in the system. After I topped it off it has worked fine all summer.

Working up from 2 pounds I think is the safe route to go if you are doing it yourself. Shops all have different ideas I have found. Because we have the last OEM R-12 based P30 I had to compute the lower amount of R-134a to use.

Again shops tell me they see over charged conditions all of the time as the cause of poor cooling. I agree to start on the low side and spend $5 for a duct vent gauge. Half pound too much is worse than half a pound too little in my experience. If one is seriously low the duct temps will be high.

Takereasy return/supply air temp spread of 26F degrees sounds good. 20-30F spread is about as good most any system is going to get in most MH applications I expect.

I find when I have a system that is cycling due to being low on R-134a that one $10 can of pure R-134a will make it function OK again. Over filling with R-134a is bad at several levels. Actually auto AC work is quite complex and many have been under trained on the subject it seems. Shade tree AC repairs can be good or bad. 🙂

[Takereasy]

Thanks John, That is exactly what I was looking for.

Doug, You are correct, sight glasses have been useless for a long time now for determining charge. No leaks, lost a condensor fan so the system wasn't cooling well. Decided I would tweak it some while I was working on it.

RPM 2000
Air into condensor (Ambient) 93F
Return Air: 77
Supply Air: 51
Suction: 30
Discharge: 275

What threw me off was, Tiffin said 2.0 to 2.5 # charge, then said the system runs 10-15 psi suction and 225-250 discharge on a 90 degree day. With that charge and suction pressure, I had a vent temp of 70 degrees, so I kept slowly adding and allowing it to stabilize until the vent temp quit going down. Ended up being about 1/2 to 1# more than specified. The vent temp rises if I reduce the charge.

[deano40]

The label on my 1997 Allegro bay says,

A/C charge capacity & refrigerant type:
38 oz - Chevrolet and Ford
56 oz - Freightliner
134a Freon

exact wording, I don't know how to post picture or I would, sorry.
Also PM sent to original poster. Good Luck, John.

[dougrainer]

Takereasy wrote:
I'm looking for the R134 Charge Weight for the Dash Air on this MH.

Chevy P32 Chassis with ACME Evap/Heater box. There "should" be a label stuck to the evaporator case with the R134 Charge Weight however mine is so faded it can not be read.

I'm hoping I find someone that still has a label intact.

Tiffin said around 2 to 2-1/2 pounds. That isn't very specific for something that should be charged by weight.

Thanks,
Richard

HOW many technicians actually charge by exact weight on a Motorhome system? Very few. Evanstempcon states 2.75 lbs for their Chevy P applications. What is so hard about 2 to 2.5????? You put 2.0 in and watch your gauges and see how it cools. If you add more, you watch the temp drop and the gauges. Once you hit saturation charge, you will see a stop in the temp drop or you will see the HI side start to go too high. Since Tiffin did use ACME, they have the specs on the charge. BTW, you CANNOT use the sight glass on the dryer to determine full charge by the bubbles. a 134a system will have bubbles on a correctly charged unit. Doug

[Takereasy]

Mine is the blended door unit and it does have an expansion valve.
Blend Air Motorhome Unit 4215030

Charging by pressures and temps is pretty much how I did it a couple years ago when I changed the compressor. My notes show it took right at 48 oz which provided the best vent temps but I wanted to be a little closer than charging by pressure and temp. 48 oz seemed excessive especially if the factory is calling for 32 to 40 oz.

[MountainAir05]

http://www.myacparts.com/rvacheaterparts.php

http://comfortairgr.com/


http://scsfrigette.com/

Look at the picture , you could have a scs also

My friend has a P32 98 but his is a SCS and it cools the best between 2.25 to 2.5 lbs and yes it did get weight the first time. Put in two lbs and add a ounce at the time if you don't get the answer you looking for. Temp plays a lot of how much.