Engine AC

Furnace, air conditioning, thermostats, distribution.
Post Reply
oldcobia
Posts: 74
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Engine AC

Post by oldcobia »

Engine ac seems to be in good shape according to gauges. I can only get vent temperature down to around 60. High side is around 200-225. Have about 40-45 ounce 134 in system. I know it’s a long run from engine to evaporator. Overnight static pressure in 90psi. Is Freon still low? Fairly new to ac systems. Thanks
CactusTwo
Posts: 50
Joined: Mon Oct 28, 2019 12:06 pm

Re: Engine AC

Post by CactusTwo »

What is your Delta Temperature, the difference between the outside temperature and the AC vent temperature. I should be up to 20 degrees, which is good Can't expect more! https://www.rvtechmag.com/tech/51_r134.php
Len and Brenda Nugent
Alberta, Canada, fulltimers since 2013
1996 Safari Serengeti 3740 front door, bought in 2019
Cat 3126 300hp, Allison MD3060, VelvetRide suspension
sold 2008 GMC Duramax 3500 and 37' Cedar Creek 5th wheel
oldcobia
Posts: 74
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Engine AC

Post by oldcobia »

So your saying my ac is working as well as expected if vent temperature is 60 if outside air temperature is 90. Why is house vent temperature at 45 in same condition
CactusTwo
Posts: 50
Joined: Mon Oct 28, 2019 12:06 pm

Re: Engine AC

Post by CactusTwo »

Basically the answer is YES if you haven't looked at the website I posted. The difference between the air going into/ past evaporator coils and output from vents have a DT however the delta temperature is an AC mechanic's rule of thumb so if you want to PAY someone to say the same thing and NOT do some internet research on your own about DT, PLEASE pay them! As the dash "area" gets cooler then the vent output gets cooler but don't expect the dash to cool the entire rig. Are you cooler than outside, GREAT! Are you in need to be cooler, then block the dash area with a curtain behind the pilot seats and window shades on front and side windows as you drive and run the gennie and rig AC to cool the living area or you can....buy a walk in freezer and enjoy it.
Len and Brenda Nugent
Alberta, Canada, fulltimers since 2013
1996 Safari Serengeti 3740 front door, bought in 2019
Cat 3126 300hp, Allison MD3060, VelvetRide suspension
sold 2008 GMC Duramax 3500 and 37' Cedar Creek 5th wheel
oldcobia
Posts: 74
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Engine AC

Post by oldcobia »

I did read the link and info was very helpful so much thanks to you. I’m thinking there should be a return on inside to continually get air cooler to a point. By not knowing the capacity of the system is the only way to determine correct amount of Freon is to go by gauge readings and vent temperature? Thanks
TDJohn
Posts: 451
Joined: Sun Oct 27, 2019 11:34 pm

Re: Engine AC

Post by TDJohn »

Len,

You're a bit cranky lately, maybe you need to walk in the freezer to cool off? ;)

From reading this thread, it seems like oldcobia is trying to understand how this all works, and trying to makes sense of it, since it is new to him, and not everyone can grasp things quickly.
He asked a valid question in trying to understand why there is a large difference between the capability of dash a/c and central a/c in a home. And the answer is not only the delta temperature, but the heat load index.

Oldcobia,
Homes usually have very good insulation, thus a much smaller heat load index, meaning the a/c does not have to work as hard and cools the home more quickly. RVs have a very high heat load index, because of very poor insulation and lots of windows. To make matters worse, on many of the older Safari coaches, their is a whole lot of air infiltration that comes through the front wall, especially while driving, and like Len mentioned, the a/c system can not keep up. It is the equivalent of leaving a refrigerator door open, and expecting the refrigerator to stay cool at 40 degrees, it's not going to happen.

Also, the dash are does have a recirculate option. On my coach, that is activated by choosing the Max a/c position. I am not familiar on the newer coach displays, as they are different then what I have, but I'm sure that option exists.
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
oldcobia
Posts: 74
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Engine AC

Post by oldcobia »

Thank you for the polite response. And yes I'm trying to learning all I can about this beast as my neighbor calls it. I run my air on max mode and I have been all under dash looking for other things and have not seen an air return. Cannot use freezer because my generator is not running at this time and I can't get very far on the extension cords I have. I do like the idea given about using a curtain behind front seats. Thanks again. '95 35' Sahara
chuckster
Posts: 219
Joined: Thu Aug 27, 2020 4:53 pm
Location: Idaho

Re: Engine AC

Post by chuckster »

Last year, I spent close to $4000 trying to make my wife happy with the AC coming out of the dash. This is an area I WAS clueless about. Went to a reputable Cat service company in my area that always has Cat pushers lined up for service and I’ve used them before for all drivetrain related service. Truly making a very long multi-visit story short, I was able to drop the always-warm air coming out of the vents by 25-35 degrees from the outside temperature, but when it’s 100 outside and you’re getting 70-75 degrees out of your vents but you’re sailing down the highway at 65 mph with the sun beating down through that enormous windshield made of sand (glass) which is a conductor of sunshine on a leather covered dash which is an insulator for that warmth that radiates through the glass coupled with the truth told by TDJohn about the front wall being “drafty” (to say the least), it’s a recipe for a “Phoenix” climate. I had a buddy drive down the highway on a very hot day while I crawled under the dash as far as I could trying to locate where warm air was coming in. I could feel some but could not locate the exact source. I have an ‘01 Zanzibar and they stopped putting in an access panel in front at some point in the years so I could not open that up and look for things that might be passing warm air.

You could have a faulty or “iffy” climate control panel not calling for cold air. That’s the first item that the Cat service center told me was happening and the issues snowballed from there in my 20+ year old motor coach. The mechanics were good in providing issues with photos of temperature and electrical readings and such but my bad luck would not stop there. They were not able to charge the system with Freon; it was escaping which led to a crack on a fitting at the compressor. Bad luck didn’t stop there either. Had to replace the compressor as well. That took a week to hunt down because it was some “8 groove pulley” something-or-other. Finally got cold(er) air after dropping 40 Benjamins but as the bill got higher and higher, one just says getterdun.

Overall the wife is happier now that my wallet is thinner and her feet are colder but we are still going to put in a floor-to-ceiling heavy curtain behind our chairs to keep the cold air in. I prefer to just use both roof airs on the gennie as I go down the highway. The dash air does make a difference that just the roof airs could not do for us but you may chase your tail and drop some stacks before you find a happy medium.

Happy wife, Happy life. Good luck!
Chuck & Mitzi
'01 Safari Zanzibar 3646 (side entry)
Cat 3126B / Allison MD3060
Magnum M-Series "Blue Max" chassis
2018 Jeep Grand Cherokee Overland toad
TDJohn
Posts: 451
Joined: Sun Oct 27, 2019 11:34 pm

Re: Engine AC

Post by TDJohn »

Another issue that I have seen, at least on the older model '95s/'96s, the bag in the receiver/dryer, that holds the desiccant beads, disintegrates and the beads cluster in and clog up the expansion valve. This will cause the system not to work and likely destroy the compressor if it is not caught in time.

BTW, this site usually has all the dash a/c parts needed for our coaches, it would be a good idea to make your a/c repair shop aware of this site so all parts could be easily and quickly obtained.

http://acmeairparts.com/rvacheaterparts.html
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
Post Reply