So it's hot out and I notice that my A/C is not working. It's on, it blows, but no cold air. It doesn't appear that anything else is wrong with the truck.

Some info-
99 Dodge Cummins with 170K miles

 

is the compressor engaging?
Clark

 

Not sure- How do I know?

 

Look at the ac compressor there is a plate at the very front the belt rides on a pully just behind the plate. If the compressor is engaging the plate will be spinning with the pully. If the compressor is not engaging there are sevral things that could cause it such as the refidgerant leaking out or an electrical problem.

 

Ok,
So I think I found the AC compressor but the plate you speak of doesn't seem like it could move. I grabbed onto it and tried to physically move it from underneath the truck but could not. Am I looking in the right place?

I am looking in the lower right side of the engine at the belts.

Does anyone else have a picture of the right place in the truck? Or if I posted a photo could you tell me?

 

Probably just needs a can of refrigerant. You can get the do-it-yourselfer at the autoparts store. It has a hose that attaches to the low end of the system( near the back inboard side of the air cleaner box). Just hook up the hose, turn on the ac, screw a can onto the hose and twist down a needle valve then back it off. If the can starts to get cold, it's charging. It takes a few minutes but it's super easy..

 

I bet the blower module is bad. I had this happen to a dodge stratus once.

 

take to an ac shop
Clark

 

no I mean the resistor not module. And it could be the control panel as well. But with the car I had it started out as not blowing cold air for ac and then eventually the heat would only work on full blast. Turned out to be the resistor AND the control panel

 

not sure where it is on a dodge truck but with the stratus its under the glove box. You take off the glove box and then stand on your head, take out 2 screws, unhook it, and then try to get it free and loosened without breaking it

 

This may sound far out but check to see if your horn works. On my 97 if the horn fuse burns out the A/C doesn't work. The fuse is in the box under the hood.

 

I use Propane to refill mine. Dura Cool is a in-direct replacement for R12 after you have tried R134a and find that it isn't too good.

http://www.duracool.com/msds/webmsdscylr.pdf

Checking the MSDS you will find that DuraCool is mostly propane and methane.

You will not find adapters for a propane bottle anywhere - I made my own. It is necessary to use gauges or monitor the glass in the drier or line for proper fill levels. Do not fill with liquid propane - use vapor - tank upright.

Propane was claimed to be hazardous by DuPont's people when they came out with R12. Now that the patent rights are timed out for R12 - all of the sudden R12 is harmful to the environment. Onto another expensive solution. Dealers will never tell you of this. Who is going to charge your A/C for $.50 worth of propane?

Note that I am just passing on information I learned from a retired group of GM dealers who RV and posted the info. Propane is compatible with refrigerant oils in use as reported by the dealers group and Duracool. Propane is a more efficient refrigerant than R12. I cannot speak for your safety in doing this - if you don't feel qualified don't do it. For mechanic safety I would label the a/c with a label that says Duracool or equivalent- flamable. Propane is listed as a refrigerant in engineering and refrigeration books.

Real safety issues - unlikely to have any hazard and no reported accident problems with it at the time I read the original posting. All in all it is much less dangerous than sitting on top of 30 gallons of gas or diesel during an accident. There is only a pound or so of propane in the system.

Once again - this is for your information only. You must decide if you are qualified to use it safely. Check out the MSDS on Duracool.

 

you can not turn the plate by hand(unless you are godzilla). start the truck with the heater on. have someone else turn on the ac, not defroster but ac, while you watch the compressor plate. if it engages the circuit is ok. keep whaching, if it starts to cycle on and off it is probably low freon, and as said before a can of freon will probably do it. if it does not engage you start checking hi/lo compressor sensors, control voltage in ect. oh yea there is a wire to the compressor clutch with a connector. make sure it did not come off or get loose.
Clark

 

I am having similar problems with my 97. It keeps blowing the relay. At $9 each, this is getting expensive to trouble shoot. Could I have bad pressure switches? or bad compresssor?

 

Do you have any IDEA of what will happen to you if that crap leaks while you’re smoking? >BOOM< There have been tech's KILLED from people doing just that. Never use any gas that can explode in your AC.

Allot of shops still use the tried and true method of a green flame to find leaks in AC's. If your vents just happen to be full of gas and a tech uses an open flame to check for leaks the gas will explode in the vent and has killed mechanics before then you’re not only liable but accountable legally for their injuries and or death. If a shop find out you have Propane in your truck's AC they will show you the door. Good GOD man think about what you’re doing. You cook with propane and heat homes with it.