Dash AC not cold

[buystockinfun]

I'm wondering if my expectations for my Dash AC are set too high. It just doesn't seem to blow very cold. When it is about 85 out it comes out about 63 out of the dash with an AC temperature gauge. I tried it on a rental car and it was coming out like 50 degrees at the same time for the rental. Never had any luck doing AC pressure readings but I did buy a gauge set. I hear if it has an expansion valve you can't get quite the right readings but then I also read that if the pressure isn't changing on the low side then you have something stuck or plugged and I'm not sure what that is.

At 85° I get a pressure of about 255 on the high side which appears from when I'm reading to be accurate but the low side is just 15. No matter how much Freon I put in there the low side pressure doesn't change and the high side pressure goes up and of course I have to evacuate that because it can't be too high I don't want to ruin the compressor. Also not sure what type of oil to put in I believe it's some kind of 46 oil but there's no real accurate information to confirm that there's a bunch of different oils. The compressor appears to be engaged fine. I did notice when I put fluid in you could see a little tiny bubbling from the high and low sides I tighten the needle valve down. This could indicate some kind of bad o-ring or needle valve that needs replaced I did put a new needle valve in one of them but I think it still has a little bubble where the needle valve is I think it also goes away though I guess when it gets agitated or something maybe they can bubble out a little I'm not sure. But this could indicate a separate problem I think regardless of the needle valve when you put 5 lb in there the pressure still on the left side never goes up above 15. So like I say two different advice that I saw on forums were that something is sticking cuz it should go up between 30 and 50 psi but then a contradictory for him said that because it might have an expansion fitting that it never will fluctuate or something but it just seems too low for me.

I can't find an AC place that will even look at it because it took camper and a diesel pusher. Maybe 63°is a normal reading with the compressor way in the back. But I really have no information on the routing or any of this for this it would be great to get a diagram of how it's routed and how many pounds it would take I mean I'm guessing it's about four to five pounds somebody said on some forum somewhere. It is r134a system.

This is a 2006 Monaco executive with a 525 horsepower isx15 Cummins engine that was supposedly upgraded to 600 HP on a Roadmaster
chassis.

Sorry for the long post but at least it's a full explanation hopefully. Not sure how to add pictures I don't see that option maybe I'm too new. Oh and most forms people don't post their solutions which drives me crazy so I promise I'll post a solution if I find one or what the final analysis was for example on the low pressure.

[Rick_Jay]

rgatijnet1 wrote:
I always just used a good temperature probe in the AC duct and added refrigerant very slowly and watched the temperature. As soon as it got to the lowest temperature and started to retreat, I stopped adding refrigerant. This worked well for me with my Classic cars with Freon 12 as well as with the R-134a. Then again, I'm no expert and was only interested in cold air from my AC unit.

Agreed. Even though I had the gauges and (usually) have the graphs as well, the procedure I followed is what you state. Take your time and it works well.

Obviously, the few times when I filled the system after it's been evacuated I just fill it to the proper amount by putting the refrigerant tank on a proper scale while charging the system.

buystockinfun, as for the shut-off valves, I just put a standard hot-water shut-off valve from the hardware store on the input heater hose to the heater core.

JRscooby, you were right, the original mention of cutting off the hot water into the heater core mentioned using vise grips. I agree, probably not the best practice, especially with older hoses which might be more brittle and subject to being damaged. I was just referring to the idea of stopping the flow of hot coolant into the heater core. 🙂

~Rick

[rgatijnet1]

I always just used a good temperature probe in the AC duct and added refrigerant very slowly and watched the temperature. As soon as it got to the lowest temperature and started to retreat, I stopped adding refrigerant. This worked well for me with my Classic cars with Freon 12 as well as with the R-134a. Then again, I'm no expert and was only interested in cold air from my AC unit.

[RLS7201]

dodge guy wrote:
A good AC guy knows how to read gauges (and I am one of those people). You have to know outside temp and humidity and have a chart to compare that to the pressures on your gauges as well as the vent outlet temperature. It can be done with the right person. Sadly not many like that left anymore!

Another trick is to put you hand on the low side line just as it leaves the evaporator and feel the cold. As you add refrigerant you will feel the line getting colder. Then you will feel a cold rush of about a 10 degree drop. That's the point when the evaporator is boiling refrigerant through it's entirety. Add 4 more oz. to make sure you have a good liquid seal on the receiver/dryer down tube and you'll be nuts on.

Richard

[JRscooby]

BTW, after years of using dealers and independent shops, I got to the point if I had AC problems, take it to Thermo King

[down_home]

Our Revolution had o rings in line replaced and filled with refrigerant several times. Finally it wasn't putting out any cool air in Kingman,AZ last year, again. The evaporator under the coach, is part of the chassis, was corroded etc. Found the only one available, or in existence apparently in Main, I think, and may have replaced the fan too. Freedom Roads in the Northeast was first Dealer, and it was apparently exposed to salt etc. I did get underneath and rinse it really good a few times, over, the 19 years we owned it.
Freightliner Service Center in Kingman got it fixed proper. Long hoses from the ac compressor forward.
Generally if they leak you will may see compressor lube and or dye leaking from the o-rings or holes or stains.
Once we got 100 miles east of Kingman we cut the generator and heat pumps off, Seldom had to use them the rest of way home. It blew cold. We many/most of the times kept the a/c set on max to recirculate inside air as there is no filters on the dash air intake, something I never got around to deigning and making. On a long trip with outside dash air everything seemed to get coated with dust.

[JRscooby]

Rick Jay wrote:
JRscooby,

I agree, and this was mentioned in the first page of posts. It would be relatively easy to add a manual shut-off valve on the inlet hose of the heater core, if there's not one already installed. It doesn't take much hot coolant leakage to overpower the cooling ability of the A/C. Buystockinfun, if there is already a manual valve installed, try shutting it off to see if that helps.

Though, that wouldn't account for your low pressure readings being on the low side.

Good Luck,

~Rick

If valves was mentioned, and I missed it, I'm sorry. I did see something about vice grips on hose. That could (likely would) cause damage to hose. Do it to somebodies rig, then charge to later fix leaky the hose is a questionable deal to me.

OP I mentioned the intake temp, and the amount of drop you are getting.
Back in my youth I took the AC out of a pickup, put in my 427 GMC. Now that truck had 2 gearboxes under a not well insulated floor, lots of other ways heat could get in. And because of the loads we carried, we would shim the back edge of hood up to let some heat from under hood. Worked on it for hours, on a 90* day, air at vent was about 75* Gave up when I taped the thermometer to the cowl in front of windshield where could read going down the road. The air it was picking up was over 140*

[buystockinfun]

Yeah I think the shut off maybe makes it more efficient so I'm not opposed to doing that. I don't know that it helps cooling the motor very much considering the size of the engine and how small that area is under the dash but I think on other cars like small cars or even trucks that can help cool the motor sometimes you're having an overheating problem you can run the heater I think I've done that before. But you're right about the low pressure thing and I think that's actually the major indicator. I have a feeling something's broke loose maybe with that dryer or something and it's plugged up the system in some way. That being said I'm told that 20° from ambient Air temperature is a great drop somebody said something about intake air temperature well let's just say that that is the same as the outside air temperature even though it hasn't been tested once you get some cooling in the cab at your feet let's just assume the temperature is the same I haven't read it but it probably is very close cuz it's blowing out and then you have the whole camper and until you're running the air conditioner in the camper it's probably some pretty warm air going into the intake vents I assume on the floor I don't really know if that's a heating vent or where it intakes exactly but assuming it's on the floor somewhere that's probably at least the same temperature as it is outside. It does cool a little better when the camper temperature is lower running the generator cooling the entire camper. Then you get a cooler sort of feel but a lot of that is because the entire camper is cooler anyway.

But if you're supposed to be getting readings like the RV guy said of 35° I just don't believe that I think coming out of that thing during the summer you'll be lucky to see 45° maybe 52 anywhere in the USA down on the lower 48 anyway I don't see 35 I mean unless you're running the air conditioner in the winter Maybe... Maybe 20° drop is the answer if it's 85 outside and it's blowing out at 65 I should be happy but it sounds like it should be cooler than that and I think it should be coming out in the 50s anyway and so therefore that kind of indicates a problem in my opinion.

I am going to probably do the diverters to block that the only have to do it one way like one valve to stop it from flowing in or do you have to put it on both sides? Also any comments about the above with the air temperature thing am I misunderstanding that I mean if it's 20° I should be good then there's absolutely nothing wrong but then why the pressure problem I think solve the pressure problem by whatever is causing that and I get better temperature out of the dash.

[Rick_Jay]

JRscooby,

I agree, and this was mentioned in the first page of posts. It would be relatively easy to add a manual shut-off valve on the inlet hose of the heater core, if there's not one already installed. It doesn't take much hot coolant leakage to overpower the cooling ability of the A/C. Buystockinfun, if there is already a manual valve installed, try shutting it off to see if that helps.

Though, that wouldn't account for your low pressure readings being on the low side.

Good Luck,

~Rick

[JRscooby]

I don't know a lot about AC systems, but if you are getting over 20* drop (85* outside, but you have not posted the temp of air at intake) I would look at side of engine where heater hoses connect. Most times there are valves to shut off flow of coolant thru heater. Much better than putting a weak spot in hose with vice grips

[buystockinfun]

I'm going to take a guess that you're right about the dryer and the beads into the expansion valve. I wonder if I'll replace that myself and then have an AC guy fill it I don't know that I'm qualified to fill the air conditioner myself but then again I don't know that I'm qualified to determine if it's the dryer or not either. Where I live it's very hard to find a good AC guy

[hughesjm21]

On one of my coaches I had similar pressure indications. I found out the dryer had an oulet screen that failed and allowed resin like beads to flow downstream to restrict flow through the expansion valve. After replacing dryer and expansion valve cooling returned to normal.

[dougrainer]

dodge guy wrote:

dougrainer wrote:

dodge guy wrote:
Sounds like it’s low on refrigerant. You would need gauges to accurately see the pressures and determine how much it needs.

From the EXPERTS on the link I posted. Gauges are good but you CANNOT accurately determine the correct charge. As I stated, TOO MUCH coolant will cause low output as well as LOW coolant. Gauges cannot be that accurate to determine that. You can get close but close will not give you the BEST cooling other than an exact charge. If I was paying somebody, I want the BEST not close. Doug

From the link.

the only way to be certain of an exact charge is to fill an empty system with the
specified amount of R-134a refrigerant.

A good AC guy knows how to read gauges (and I am one of those people). You have to know outside temp and humidity and have a chart to compare that to the pressures on your gauges as well as the vent outlet temperature. It can be done with the right person. Sadly not many like that left anymore!

"the only way to be certain of an exact charge is to fill an empty system with the
specified amount of R-134a refrigerant".


That is exactly from the Manufacturer of the Largest Maker of RV dash AC systems and obviously from THEIR Engineers in their manual. I also know how to read gauges (42 years of experiance). Doug

[dougrainer]

buystockinfun wrote:
Are those some kind of special inserts or are they like just something you buy for a tire? In other words did you buy them from an air conditioning place or can just pull one off the shelf of Walmart for example? Thanks

NOT tire. especially 134a fittings. You can go to most large Auto supply and tell them you what Hi and Lo side 134a valve cores. Doug

[buystockinfun]

Are those some kind of special inserts or are they like just something you buy for a tire? In other words did you buy them from an air conditioning place or can just pull one off the shelf of Walmart for example? Thanks