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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29523
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2008 Silverado HD2500 Duramax (170,000 miles)..AC

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2008 Silverado HD2500 Duramax (170,000 miles). AC not as cold as it should be.. and conditioned air feels damp. How can I check myself w/out any specialty tools. Autozone a mile away if there are some inexpensive means of testing. Don't want to waste money on "recharge canister of freon if it's just going to leak out in a month or two. THoughts?

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

IS this on both sides or just one?

GM Tech (Cam) :

Are you testing with the system set to max witht he recirc on?


both sides (drivers and passengers) outside temp 88 and high humidity (Atlanta GA). I have an 07 Yukon XL so I know what feels RIGHT. Yes, tested at various settings, as I stated in description, recirc feels cooler (not cold but closer to normal) and somewhat drier than without "recirc" on.

Do you have an AC gauge to check the pressures?
IS the rad plugged up so the air does not flow as freely?
Ok, then you are likely loosing some freon.
YOu will need to top it up. I Would consider pushing a bit of dye in there so when it leaks you can see the yellow oil on the component to easily find it.
Customer: replied 6 years ago.

I can get a canister from Autozone, correct? I doubt it has a dye in it, or does it? IF not, how would I go about injecting dye?


As for AC Pressure(s), I can use the "borrow a tool" program at Autozone to check the pressures, I think. Is it a process you can explain or is there a utube clip that shows it? What pressures are considered "good"?

The dye is usualyl suspeneded in oil and the ones I always used were like a caulking gun, you attach it to the low side and put a pump or 2 in.
Find the blue cap on the passengers side and attach the gauge, start the engine turn the ac on and watch what it does. We are looking to see the low side fall down to 30 psi or so, then the AC turn off, pressure rise to about 50 then turn back on and do this in 5-10 seconds.
High side we need to see well over 100.
Customer: replied 6 years ago.

Sorry for delay in reply... had a chance to take vehicle to a mechanic for a free analyis. His opinion is that since it doesn't have a cabin filter, that the coil may need to be cleaned with an aerosol coil cleaner, which can't hurt. Your thoughts?


As for the freon level, despite the mechanic's opinion that the freon level is probably fine, (he didn't put gauges on it to test pressures), I think that the freon might be low. It takes too long to get cold (at the vent). He tried to sell me on the truck being black and the interior being black leather and that was why it was taking longer, but honestly the air is not as cold as my 07 Yukon XL and it takes considerably longer to cool the cabin, again which is smaller than the huge cabin of the Yukon XL.


I plan to try to borrow a set AC pressure gauges from Autozone and get a canister of freon in case it is low, as I suspect it is.

OK, let me konw.
Customer: replied 6 years ago.
Hey, I just bought a canister of freon with a low-side pressure gauge to monitor the pressure as the freon is added. I just want to make sure I understand which is the "low side" that I am attaching to . On my 08 Silverado, there is no BLUE cap as you reference above, both are black and unmarked. Is the low-side the larger of the two pipes or the smaller of the two?
Ok, the port us the smaller one and the fitting will go on one only.
Customer: replied 6 years ago.

Added freon with no issue.. Didn't realize the ports were different sizes. Duh... Anyway we'll see how much of a difference it makes for now. If no difference, then we'll try cleaning the coil under/bnehind the glove compartment.


Just as a last question, it seems like this truck produces alot more condensation drainage than any other vehicle. Does that give you some idea about what else might be wrong?

That is simply an indication of how humid it is there. Draining water is good, because it means that part is working properly and the system is cooling.
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