You will need to replace the Accumulator/Drier if the system has been "dry" for that long.
It is not expensive, $25
If it was leaking and low on "freon" then when you accelerate, the compressor pulls out "freon" from the cab and pressure drops low enough for cycle switch to go off and cold air stops until pressure returns.
You can get a UV die that goes into the lines, then you need to charge the system and run it, then you use a UV light to try and find the leak, but if you can hear it then just get a friend over
Or you may want to take it to a shop and ask them how much to find the leak.
And then replace what needs replacing yourself.
It is best to rent an AC kit, with the multiple gauges, in this instance, you don't need a simple recharge.
Google: how to use ac manifold gauge set.
AC is not complicated but there certain things that are must haves.
Refrigerant(freon) is a liquid but ONLY when under pressure so when there is a leak the refrigerant comes out as a gas, and leaves no residue, so hard to find any signs of a leak.
(But it will be very cold at the spot of the leak, read on)
When you compress anything it will heat up, like compressing air, and when you uncompress anything it will cool down, like air, i.e. a spray paint can, as you spray on the paint the top of the can gets colder, because the compressed air in the can is uncompressing as it goes out.
The refrigerant used, R134A, gets very hot when compressed and very cold when uncompressed(decompressed)
So the compressor does just that, compresses it, then because it is very hot it must cool off a bit so runs through the condenser, in front of the radiator.
from the condenser it goes to the accumulator/drier, this is like a reservoir for the hot "freon" and the drier absorbs any moisture caused by condensing.
From there it goes into the expansion valve, where it decompresses and gets very cold, and that cold "freon" runs through the evaporator in the cab where the blower circulates air thru it to get cold air out of the vents.
Then it goes back to the compressor and starts all over again.
There are also 2 pressure switches, high pressure and low pressure, in 2008 these switches are the Ground for the Compressor relay, so compressor will not turn on if either of these switches is "open"
My guess is that the low pressure switch is what was causing your warm air on acceleration
Last edited by RonD; 07-08-2016 at 05:39 PM.