My A/C has been out for over two years. I bought one of those A/C recharging cans and tried to recharge my A/C. After recharging with truck running and fan on high I killed the truck and could here a hissing sound as if there was a leak. What is the best way to pin point this leak.

Another thing is that when A/C did work and I would accelerate quickly it would blow warm air for a minute or two before blowing cool air again. Why was this happening.

 

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

 

Thanks for the great information. I will not bring it to the dealership. I am a fix it my self kind of guy. The dealership is to expensive and they don't always fix the problem. Can you find these AC tester kits at O'Reilly s. If you could also read my thread on my Pinion Seal problem that would be helpful. Once again THANKS!

 

No, a Ford dealer wouldn't be my first choice either.

I was thinking of an AC shop, independent, that would check the system, find the leak, give you an estimate, and then you fix it.
Because finding "the" leak, or "all" the leaks will be the hard part, the rest is just wrench work.
And it can get expensive pumping in refrigerant when trying to find a leak


Unless you plan on servicing AC units for other people you just need to rent the AC manifold gauge kit.
Call local tool rental companies, they will have them for rent, and get the Brand of the kit they rent, then find it on-line and download the instructions, so you are not starting from scratch when you get it.
You can buy AC manifold gauge sets for $60-$400, can't say the $60 are not good, but............grain of salt.
I have rented the $400 models for $30 and never had an issue