I hope this is the right place to post this question. If not, moderators, please feel free to move it.

I recently had some service work done on our 2009 Supercrew F-150. Because we are in the grips of a heat wave, I asked the service manager to check the A/C to make sure it was working at peak efficiency. He said there was absolutely no way to check anything. All they could do was empty the system, pump it down and fill it with the factory prescribed amount of freon. $$$$

Is that true?

I remember "old" service manuals outlined different procedures to determine if the system had too much or too little freon. I can't imagine a modern truck with no way to check the A/C system. Can anyone set me straight? Thanks.

 

Wow!! I have never heard of that BUT my truck is a 1995 so I have no idea. Sounds weird though.

 

....absolutely NOT TRUE!! If the system is working, don't mess with it ....and especially don't allow those "service" people within 100 yards of your truck. They seem to be most interested in the efficient emptying of your bank account.

If you must, attach a manifold guage set to the high-side and low-side system pressure ports, start the engine at fast idle, set MaxAC, 60F (or max cool), blower on high, doors and windows closed.
Look for low-side pressure cycling between ~27psi and ~47psi as the compressor clutch turns off and on. The "on" clutch cycle should run 10-30 seconds. If the clutch is short-cycling, 5-10 seconds, the refrigerant charge may be low and should be replenished to establish the above criteria. High-side pressure will vary depending upon ambient temperature, but usually runs between 180 and 250psi. A low refrigerant charge will have the pressure more to the low end of the range.

If those criteria are met the only other testing would be to ascertain that the various vacuum valves under the dash are operating and directing the AC airflow dependent upon a setting: ie: MaxAC, Vent, Defrost, etc. The discharge temperature (blend door) control can also be checked by rotating the temp dial, if so equipped, from max cold to max warm.
Max cold temp setting should produce a dash register output around 50F, and that will vary quite a bit depending upon ambient temps.

PS: The refrigerant is R134A not Freon, but we all know what you mean.

PPS: To give the service guy his due the only way to determine the exact
amount of refrigerant in the system is to evacuate the system to (-)28in/Hg
or better and then recharge with the recommended amount of R134A....35fl/oz as I recall.

 

Thanks Kattumaram for the good info. I was sure there had to be some way to check the overall operation of the system. Thanks for the validation. The system is working so I will keep the service folks away from it.

And yes, I only used the term Freon generically. It's kind of like asking for "Coke" when ordering a soda. Old habits die hard.

Thanks again.

 

I agree it would have made sense for him to say, "we can hook it up to the machine, check the pressures and evacuate and recharge the system for you sir" and you might have bought an AC system check. He's a bad salesman and probably a bad service manager. However I disagree on not letting trained techs work on your AC system. They have the proper tools and machines to service the system correctly. A set of gauges and some refrigerant in a can isn't going to get your system running the way it should, it's best left to professionals.