mega cab ac sucks!

[tobaccogrower]

anyone with a stick notice there truck sounds like a school bus because the fan is always ingaged? mine is so bad i feel the power being robbed from the motor. when fan clutch kicks off truck has more power.

 

[GCroyle]

Mine is a stick, '05 and no it doesn't make that school bus noise. This has been one of my challanges to diagnose.



Bizare stuff I've tried so far:

Bought dual AC gage and hose set.

Side by side comparison to companies '07 manual observing fan and AC PSI, inconclusive.

Hooking up a timing light (ready for this) to my Cub Cadet mower just so I could even start to freeze frame the fan. Yup I remember seeing it ramp up and down.

Trip to trusted dealership, inconclusive works per diagnostics.

Purchased new Dorman fan clutch from Geno's. Not installed, actually returning due to TDR observations that it don't always work right.

Put box fan in front of truck (driveway stationary) trying to up the airflow, yeah right.

Drivers and Pass side thermometors, pretty even.

Recorded pressures, IIRC it definetly did cycle.

Watched TDR threads, posted, inclonclusive.

Engine temp has only hit over mid 190's on PDA when towing my TT.

Just did a coolant change, hoses, t-stat and that was a PM function only.

Don't forget the airflow ducting, posted earlier.

For me, it takes a fully warmed up engine and airflow and for coolest temps recirc.

 

[jelag]

I have to chime in here... after several of these trucks... and they all seemed to work the same, I just assumed that the engine ECM didn't allow full cycle time on the compressor because the engine wasn't up to temperature... . just like it doesn't allow the alternator to function until the engine reaches a certain point for it to be stable. .

I'm sure either Bob4x4 or Sag2 might answer this for us. . but until the engine is stable in my truck (read past trucks as well) its just not up to 100%

BTW I agree with the low 40* at the vent when its on and up to 100%

Just my thoughts

 

[GCroyle]

Jim,



Always good to hear your thoughts, you retired no time clock, no customers, no issues sorta guy.



Humphhhffff.

 

[sag2]

The more air directed THROUGH the condenser the better the A/C cooling should be. It will get rid of more heat and the liquid refrigerant should start off a bit cooler.

 

[GCroyle]

These shots are from our '07 basically the same setup as my '05. There is a lot of room for the air flow to sneak in around the condensor or radiator. Notice the gap behind and below the radiator frame.



Sag2, now we need a TDR version of the fan diagnostics. Thanks.

 

[GCroyle]

Its about 88 degrees out with pretty high humidity just returned from a 10 mile run to town and back, engine temp is high 180's. AC on engine at idle.



Quick gage observations.



Lo 24 psi Hi 220 psi FAN "strong" but I don't think is is the same fan as if the engine was at 195 degrees or so.



Maybe 15 seconds between cycles readings:



Lo 55 Hi 275 with fan slowed to "lazy" slow RPM.



It just cycles between low fan RPM and higher fan RPM and the gages just follow along, its predictable.



If I can maintain a good flow of air highway speeds above 55 or so, works pretty good. Engine has never shown signs of overheating on gages.



Is my system low and cycling or is it fan cycling because of engine temp and right on the edge of full fan power? I dunno.



No claim of AC system understanding on my part, fire away.