The air conditioning is lacking. In cool time of morning it blows cold air, but once the temperature rises outside it stops blowing cold air??
Throw some gauges on it and let us know what the pressures are running when its blowing warm air.
Also known for getting evaporators and ducts blocked with cr@p & crud. Sometimes only a complete disassembly of the ducting, clean the evaporator, pull the radiator apart, clean the condenser, etc, etc. will work. Need a S/No for more specific details - too many options out there.
I know about nothing about AC systems, shop always farmed that out once we started getting equipment with those on them. But the one thing I do know is cleaning things is critical. Any place air goes so will dust and cr@p and a little moisture turns the stone dust to cement and no more air flow!
Unfortunately cat packs most of the AC into a little black box but that being said once you open it everything is right there. I always check the charge first then like Nige says if that's good the thermostat may have fallen out of the evaporator, the evaporator could be full of dirt, air filters could also be clogged. What is the temperature at the vents and what is the ambient temperature at the same time?
I generally go first with anything that doesn’t require special tools, so for me I’d be checking cleanliness inside the black box and the duct and simple things like belt condition & tension first.
I often said the best mechanic is a lazy and cheap one. I always tried the easy stuff first, check fluids, wash machine and stuff like that. Then if there was a point at which replacing a part seemed the way to go and I was not sure what needed replacing, replace the easy $5.00 part long before going for the hard to reach $1,000.00 part. Now if we can convince someone with a D9H to follow that plan we and him will be money ahead!
What year model is your 279D? I've got a '16 that after 3 years still blows ice cold.
It's a 2014.
Thanks for all of the responses. I now have some where to start. Will post results when I get them.
Post a Serial Number and I will put up an illustration of what your ac looks like inside.
Come to think of it, have you replaced both the filters (fresh air & recirc) with new..?
GTL00687
I don't recall doing that.
No air flow no cool air! Replacing those on the quarry equipment was at least every engine oil change warm or cold weather!
Damnit..!! Beaten to it by Hansen. Really.......... Do you not change the engine lube oil filter and fuel filters also..? They're all kinda part of a regular preventive maintenance program. Another question. Do you have an Operation & Maintenance Manual for it..? If you don't I can give you directions on how to get one. Probably the best $50 you will ever spend........... Attached is how to change the aircon filters. Part Numbers are 265-6618 and 265-6619. I suggest that you change both as a first step. Price is about $50 the pair. DO NOT mess around trying to clean them, especially at that price. There is also an attachment of how to D&A the aircon and the heater. I don't recommend you disassemble the whole thing but Steps 6 & 7 of that procedure are relevant because they show you how to get at the core which is probably by now full of a mixture of dust & cr@p that resembles concrete. A lack of air flow through that core will also put a serious crimp in the way the a/c functions. While you're at it, go for the trifecta. Open the door at the back of the machine and give the a/c condenser a good wash, just for sh1ts & giggles.
Here's a couple of illustrations showing what the box looks like. The blower motor is down in the bottom.
That looks like a heat only unit. Where's the evaporator?
Well.... no wonder it won't blow cold...
Nevermind...I sees the orifice tube.
Just fixed the AC for one of my customer's 299D the other day. Heat valve was stuck on. Ac just couldn't overcome the heat output of the heater core once warmed up. Make sure hot coolant is not flowing through there.
Good point. If the flow control valve for the hot water won't completely shut off you'll never get really cold air out of the a/c once the engine warms up.
If that's the same as in my 248B, the flapper plastic is durable, but some little HVAC engineer decided to perimeter the flapper with an Oring. Damned Oring falls apart and heat wont shut off.
Update on water valve
That Oring is for the tube insertion connection, so coolant doesn't externally leak. The Oring I'm referring to is integral to the internals.
Ok, the primary and secondary filters were filthy. Put new ones in and now she's blowing about 48 degrees. According to my $2.99 harbor freight thermometer.
Good to hear but if changing those filters got overlooked then what else is lacking in terms of preventive maintenance that might cost you a lot more than a couple of new filters when it goes bang..? I ask again, do you have the basic Operation & Maintenance Manual..?
I have the maintenance and operation manual that came with the machine. I am up to date on oil changes and hydraulic oil changes. Keep the air cleaners clean and up to date. Over looked the cab air cleaners.