I have a 97 Dakota with a check engine light on. We hooked it and it said it was because of the air conditioning (though I don't remember if it was more specific, I can find out). The air blows kinda cold, but definitely like it should. It seemed reasonable that it needed to be charged, so I bought a can. I haven't used it yet though because a few things seem off. So, first of all, the pictures in the Hayne's manual do not match my truck at all. So it goes. From everything I've read, the low pressure connector is the one on the compressor, as well as the larger tube. I've also read that the quick connect will only connect to the low pressure side. Well, the inlet on the compressor is too big for the quick disconnect. There is another quick connect that it does connect to, that is on the passenger side, front. However, when I hook up the the pressure gauge, it is reading 70psi! It should only be around 30 to be charged, correct? Also, the one I can hook it up to is cold when running, and the one I can't is hot. That seems to be correct. So, I am not sure which is the low pressure line and which is high pressure. And, if I am hooking into the low pressure and it's reading 70, maybe charging it is not the problem. I have included a picture of all this. The green circle is the one I can hook into, the red circle I cannot.

Thanks in advance for your help,

Craig

 

i am pretty sure red circle is high pressure and green circle is low pressure. as far as the pressure goes. is you a/c compressor running when you have the a/c and blower on high? is the a/c compressor cycling off and on?

When the compressor kicks on (which it will only do when the pressure is above 40 psi) the pressure will drop. If the lines are full enough, the pressure will remain around 40-45 psi while it's running. When the compressor kicks off, the pressure will rise to 90-100 psi., as the high and low pressure sides even out in the expansion tank.

 

Thanks, I'll check that out when I get home tonight. I think I remember reading that it's not supposed to cycle on and off, just stay on when the A/c is on max. Is this correct?

 

Also, I know this is probably a silly question, but how do I know the if the compressor is running? Just by feeling it vibrate?

 

you will see the out side of the ac compressor spinnin when it kicks on. and it will cycle on and off as you add to it till it gets above 40 psi like sl2 said. start your truck and turn the ac on full max. then hook up your can and see what it says. if it goes below 40 psi it will kick the clutch and your compressor will stop spinin. hope this helps. p.s i added some freon to my truck not to long ago and the green circle is your low side. you cant hook to the high side unless you have a manifold set

 

Update:

So I turned the truck on for a bit, the compressor did not kick on. I found the low pressure switch and jumped it, then hooked up my gauge. It had dropped from 70 to 50, which still seemed high. I borrowed the gauge and was told it read high on another car also. So, I hooked up a can and emptied the whole thing into the system. I had a thermometer in the interior vents the whole time. When I started it read 61F, by the end it read 58F. After emptying the can, the gauge read 65PSI. Also, the check engine light is now off, and the compressor kicks on on it's own. I am very nervous to add refrigerant due to the high readings, but I feel like it must have been low if the compressor now works and the Check light turned off. Is there anything else it could be? In the compressor not functioning correctly and that's why I'm still getting not so cold air at that high pressure? Any thoughts would be great. Thanks guys!

Craig

 

the compressor may be on its way out and the compressor should cycle on and off as the pressures fluctuate and if the pressures are to high it will also cause the compressor to not work right and not cool the air down

 

So it's possible I overcharged it. Is there a recommended way to reduce pressure from the low pressure side?

 

not legally you have to take it to a repair shop the EPA frowns upon discharging freon into the air and fines can be several thousand if caught,
i like to take it to a shop to fill it up because down here its like 60 bucks and they put the right amount of freon in and check the cooling system out when doing it