Scotty,
The air conditioning in my truck has stopped blowing cold. Initially I got one of the A/C pro cans with the gauge built in, and the gauge immediately went to red and stayed there without any change I made in the cab. Sure enough after learning where the compressor actually is, I can see that it’s not engaging. The heat in the truck works fine and everything blows strong. A mechanic I spoke to isn’t convinced the compressor is done for and insist that I look into the hvac control module in the cabin. By the way, all fuses and relays related to the system are fine. Is there any validity to checking the control module? If not, where do I go from here?
thanks!
You can't do any real diagnosis with those "recharge" cans beyond that since it stays "in the red" you have little or no refrigerant. (Really all it's saying there is no pressure in the low side of the system but it can be surmised that at rest the high side will be the same unless there is a blockage somewhere.)
Under those conditions the low-pressure cutout switch prevents the compressor from engaging. You have a leak that needs to be found and fixed. A proper gauge set should be used for diagnosis and charging, using pure R134a with no potentially damaging sealers.
I thought the red area on those recharge cans meant the pressure was too high on the low side. I don't remember now, using real gauges kinda makes you forget the bad way of doing this, haha.
Hmmm, I was thinking it meant that red was for low pressure, but I've never used one of those cans before, just seen them on the shelf. Seems much more likely though that pressure would be too low with a 20-year-old truck. But you can't really do any meaningful diagnosis with those "recharge" cans.
When I diagnosed my Ranger's A/C I used one of those cans and just shot refrigerant in to see if the compressor would engage. I didn't care cuz it didn't work at all. It kicked right on. I chased the refrigerant with dye and found the condenser was bad. I was thinking in this case, if the gauge is reading high pressure, then the compressor isn't engaging. His question seemed to me to indicate it suddenly stopped working. Maybe @Jkn1349 can fill us in.
Some systems do have high pressure compressor cutouts as well as low pressure. But if pressure is that high it means someone grievously overcharged it.
I was thinking the system might be in equilibrium. The needle in the red when it's not operating could indicate that depending on the pressure and temperature, but those gauges are pretty crummy. To really know, the high side pressure needs to be known as well.
Never trust those cans of refrigerant from the auto parts stores.
Alright guys I appreciate the responses. Let’s see if I can give some more detail. Basically one day it blew cold, next day it didn’t. My thoughts were okay it needs refrigerant, as a quick fix to hold me over. In fact I do recall smelling it in the cabin in the past, so I began to think it was a slow leak and I’d simply let it fester too long. (Bare with me I’m new to this)
with this said, the a/c pro can based on the instructions states that if the gauge reads low, you add refrigerant. If it reads high (in the red) there are deeper issues beyond refrigerant levels. The mechanic I spoke to, who was very cooky by the way, claimed that taking a look with his set of gauges he can see that there is “plenty of refrigerant” in it.
I know that’s a bit of a run around, but let me know if this rings any bells.
thank you all!
The instructions for diagnosis on the AC Pro can are not of much help. You cannot tell what's going on inside your AC system with that thing. If "in the red" on the nearly useless low side gauge on that can means excess static pressure you're either overcharged or have an obstruction in the system that has resulted in high pressure on the low side. What are the actual system pressures? I'm not talking about "in the red" or "plenty of refrigerant", what does a manifold gauge set tell you when you hook it up? Although static pressure (compressor not running) doesn't tell you a lot it will tell you if it's in an acceptable range where the AC compressor will turn on. Either you have an electrical problem or a mechanical problem and there is not yet enough diagnostic information available to even attempt sorting it out.
Alright, I understand. @ChuckTobias and @JustinShepherd, I appreciate the insight, I’ll have to acquire some gauges and get some more information for you guys.
A gauge set suitable for occasional home use is not that expensive and will provide a lot more information than those cans, plus if necessary you can charge in pure refrigerant free of sealers. Here's one on Amazon for about $30:
https://www.amazon.com/Orion-Motor-Tech-Conditioning-Maintenance/dp/B08V5JWJSB