A/C Question

[Luis]

102K on '01 LB7. In the last 60 days I have been on two long road trips, one with trailer in tow and the other empty. After running 300+ miles on each run, the A/C started to get warm. Found Auto parts store and bought 134A w/hose to top of system. System did not take entire can first trip. Second trip did the same thing. (Still had remainder 134A with me.) Toped off and system did not take much. Still have some product in can. A/C works fine but now I'm not sure if it is as cold as before. Any ideas or sugestions? Thanks in advance...

[Mark Rinker]

Get the gauges on it.

If you overfill you can burn out the pump. If its cold, but intermittant, you may have a bad high limit switch, or be overfilled. If its still warm after adding, the system may have to be purged and refilled.

Either way, you need gauges and some working knowledge to keep the newer systems happy. Compressors are expensive...

[Luis]

Thanks for the advise...I'll have it checked this week. Should I leave it turned off until then?

[BradL07]

I'm not an a/c expert, but your situation sounds like the bad low side pressure switch on my '01 LB7. It's a $30-$40 part that you can replace yourself, on the condenser.

[chipper]

I'm not an a/c expert, but your situation sounds like the bad low side pressure switch on my '01 LB7. It's a $30-$40 part that you can replace yourself, on the condenser.

X2 It just screws on.

[Mark Rinker]

Actually, I think my C4500 needs the same thing...just the pressure switch on the side of the round silver underhood tank?

[Robyn]

Mark hit the nail on the head.
Get tha gauges on the thing and see whats going on.
Too much 134 will get the system too soggy and can stall the pump and do damage if let go.

In warm weather the low side pressure should pull down to about 35 or so at an idle and the high side will run about 200.
Once there is air flowing through the condenser good the low side can and will drop to about 25 and then shut the compressor off and then cycle onand off as the pressure rises and falls.
The large aluminum canister is the acumulator. It filters out any liquid that finds its way out of the evaporator and also soaks up any moisture with the desicant bag thats inside. It also helps filter out any debris.

On a GM the low side switch screws onto a fitting on the acumulator that has a schrader valve and it can usually be done without losing the charge.

[Luis]

I'll get it checked out first. If I change the switch I know something else will be wrong. I'll advise one I can get it into a shop...Thanks everyone!

[hogmotors]

I hope that you got your A/C fixed LUIS.
My guess(& ONLY THAT!!)would be the cycling switch on the accumulator("that round can on the firewall-great description!). You probably overcharged it is why is didn't seem to cool as well.
A word to all....these systems carry a small charge & it is almost impossibly to "judge" the charge by the guage readings other than VERY high or low. The systems are very charge sensitive AND if you add ref. w/o lube you might be in trouble.
Best let someone evacuate & WEIGH(I can't emphasize that enough!!)
in the correct charge.
The switch on the condenser(on some mods.) is the high side protection.
Another point....the later systems use pressure transducers(that look like switches)...if you "jump" these to test, YOU BOUGHT A BCM. The system is looking for a reference voltage signal.

& another point....if you purchase ref. in a can, I'd recommend againsted the stuff containing "sealer" or whatever.....it couses great trouble when you finally do the repair & I'm not aware of any instances where it worked. Down here the systems usually leak at the compressor case seals anyway.
sorry about the "book"!!
Gordon

[Luis]

Sorry I've been away...It seems to be working fine..I was looking at the switch and it's connection...kinda jiggled it around and pushed it in tighter, now it seems to work much better. Could it have been a poor connection? Also [this is probally stupid question] which should be on, the recirculate air or exterior air button or should they be off?

[Robyn]

Its possible the connection was coroded.
You can use either recirc for very hot days so you dont start with hot air but instead recool the inside air for colder air from the unit.

Basically as long as you are happy with how cold the air is its good to go.
Outside air is nice to keep things fresh inside BUTTTTTT when its hot outside the recirc will do better job.

[NutNbutGMC]

Sorry I've been away...It seems to be working fine..I was looking at the switch and it's connection...kinda jiggled it around and pushed it in tighter, now it seems to work much better. Could it have been a poor connection? Also [this is probally stupid question] which should be on, the recirculate air or exterior air button or should they be off?
Seems you may have answerd your own question and thankfully so with the heat like it is. Glad it's putting out like you want.

Here's my take on AC settings. I leave mine on year-round. I get heat from the warmer setting. My theory on this is that the use of an AC year-round keeps all of the seals lubricated and the uint never sits idle. So far, I have always had success doing this. I think leaving a unit idle for months on end does more harm than good.

As for the recirc? I keep my recirc on most all of the time. I do this to keep the outside roads smells outside. If I need to vent the cab, I'll open the outside, allow some air to pass through (such as a big ol' plate of to-go Texas Roadhouse ribs that have smelled up the cab), and then close it back to a preferred recirculate.

[Luis]

Thanks everyone. I like the idea of leaving the A/C on year round and adjusting the temp as needed. I’m obviously not an expert but seems to make sense reference the lubricant. As far as the different setting’s, kind of what I was thinking but I wasn’t sure. Thanks to everyone once again…;)
P.S. sorry about the previous misspelling [probably]. :eek:

[cryodrene]

I live in South Texas and it gets HOT! down here. When it is like that my A/C just won't cool the truck down. On road trips I sweat and sweat. I took it to the dealer and they said everything was fine and that the Diesel a/c is not going to cool that well in the summer. I took it to a different dealer and they basicly said the same thing. I think its a load of crap but what else can I do? You guys have any ideas for me? I have a buddy with the same truck as me except its a gas and the a/c will keep beer cold if you need it to.

[DmaxMaverick]

I live in South Texas and it gets HOT! down here. When it is like that my A/C just won't cool the truck down. On road trips I sweat and sweat. I took it to the dealer and they said everything was fine and that the Diesel a/c is not going to cool that well in the summer. I took it to a different dealer and they basicly said the same thing. I think its a load of crap but what else can I do? You guys have any ideas for me? I have a buddy with the same truck as me except its a gas and the a/c will keep beer cold if you need it to.

It doesn't have to be that way. Problem is, the dealer has a standard that is too low for your condition. Regardless of year model, it should do very well, and it can if it doesn't. My '01 will blow 35-40° air (beer cold) when driving in 105-110°. In town, it's about 10° higher in normal tranny mode, and a bit cooler with T/H engaged. T/H allows for higher RPMs between shifts and locking the TC lowers tranny temps that find their way to other systems. Idling will never get above 55-60°, even in a 120° parking lot. There is no reason why every GM truck can't have it this way, and the dealer is full of it when they use the "it's not a gasser" excuse.

[spongebob]

cant believe they sell those small cans of 134 in the store..
anyway, if your compressor clutch is in and turning, the low psi switch is working..

[epa1775]

Dmax,

I live in 29 Palms and have the same problem as Cryodrene. I'm driving to Texas this weekend and then to Utah a couple of weeks after that. What does your system do/functions that mine doesn't? Are there any changes I need to make to any of the settings. Thanks for the help.

Pete

[DmaxMaverick]

Dmax,

I live in 29 Palms and have the same problem as Cryodrene. I'm driving to Texas this weekend and then to Utah a couple of weeks after that. What does your system do/functions that mine doesn't? Are there any changes I need to make to any of the settings. Thanks for the help.

Pete

29 Palms. That's hot!

I didn't make any mechanical changes. Just adjusted the freon amount until it was just right. From the factory, they charge them within a range, and as long as it blows cold under their conditions, it leaves that way. Get yourself a gage set, some freon and a good chef's thermometer (they're the most accurate and fast). You can use a cheapy Walmart charging kit. The gage is the most important part, and I've found them to be pretty accurate. Most of the time, believe it or not, they are overcharged. Try dropping the pressure to the lower end of the scale and work up from there. My '01 is best at the top of the scale (50 psi suction side), while my Impala works best near 25. I've tuned other Duramax trucks and none of them are the same, but generally work best above 35 psi. That's suction side pressure at about 1500 RPMs, at highest fan setting and recirc. The outside temp has to be pretty high when you do this or it won't be the same when it does get hot, and it will cycle off because the pressure gets too high. Watch the thermometer (placed in a center vent) and let it settle about 5 minutes between changes. Other than that, make sure your cooling stack (condensor, CAC, radiator) is spotless. It doesn't take too many flutterbys to reduce the efficiency of the condensor. Also, if you have a cabin air filter, it helps if they are clean/new.