Hi All I have a 2010 cat 305dcr closed cab. JXER00267 The ac has been starting to feel a little weak. I believe it needs a charge of Freon I have the gauges and bottle of gas. My question is what should the pressure be in this small air conditioning system? Thanks Adam
Not knowing anything as to whether it's expansion valve or orifice in the system, I always shoot for around 30psi, at idle, on a hot machine.
Thanks heymccall I didn’t know the system should be hot first. Would the pressure be different if it is expansion valve or orifice? Or is it not enough to matter?
First thing check your airflow (cab filters and ducts) on the machines that work in dusty environments the blower wheels often go bad. Then check the condenser coil (outside) if condenser coil is dirty you are not gonna be able to properly adjust the charge. If you have both gauges then google the charging chart and charge your high side according to your ambient temp. If you charge very hot cab to 30 psi. then when temperature will drop to comfortable 75*F the coil might start freezing. Your freezing pressure is 27 psi.
Thanks TVA I know the filters and condenser coil are clean , I do that regularly. But it doesn’t seem to blow as hard as it used to. How would I know if the blower wheels are bad ? Will it be obvious?
Take the squirrel cage and inspect visually, check ducts for obstruction ( pack rats can do weird things, I once had mice living in a truck that was driven every day.
Check your low side pressure after 15 min of A/C running if it is 28-27-26 psi the condenser coil might be freezing over and blocking the flow.
I was just reading the charging chart. Lots of other info there. I’ll start Monday by checking the fan , ducts ,inside coil and drain hose then move on to pressure. Thanks for the help
I believe the only proper way to check is sub cooling. Get your gauges on it and run it on high with the engine at a high RPM and allow it to stabilize. You need an accurate temperature gauge (voltmeter thermocouple) taped to the condenser liquid outlet. Whatever the pressure gauge indicates for temperature on the high side, the liquid leaving the condenser should actually be 10-15 degrees lower than that. This tells you that the last few turns of the condenser are solid full of liquid, a little operating reserve for leaks and such. If it still works bad after checking this way, the problem lies elsewhere.
We have a lot of issues with brushes wearing on a/c blower motors due to the amount of dust they ingest. If you tear into things down to the fan motor make sure that you check the brush condition on top of anything else while you're in there.
That’s what he has the charging chart for, and you right about accurate thermometer!
Charging chart only works if the condenser is as efficient as the assumptions in the chart. Always measure is what I say.
Thanks guys I now realize the ac system is more complex than just shooting a can of Freon in it. Monday I’ll start at the fan and work out
Wondering if someone has breakdown of the in cab fan and coil assembly for the AC Cat. JXER00267 Thanks
Thanks heymccall Very helpful I see I have to evacuate the system to get to the fan and coil. Try again tomorrow.
I'd stare hard at that unit before evacuating the system. Almost looks as if you can split it in the machine.
I sure did stare at it a lot yesterday. I think it can be split in the machine if there is some slack and flex in the ac lines where they go thru the floor.
When in doubt i evacuate and see how much came out i can charge in the field using just guages but that is only for top off and just getting it working. I have run into so many oil slugged and over charged systems in my 18 years when ever i can i hook them to the machine and see what was in it , charge it back to proper amount by weight per oem and then trouble shoot from there as long as cabin air flow was good , i deal with mostly macks so i usually go straight to a evap coil cleaning first thing and then see what it does .