A/c Issues

[Blue88Comanche]

I had a guy at work try to find the AC coolant leak on my Jeep today, we put 1 1/2 cans of coolant and the compressor would not kick on.  so i touched it to the battery and it still works.  we let is cycle some then i hooked it back up properly and it still would not work.  we had pressure. I swapped all the relays around with my fuel pump and they all worked. the fuse is good.  

 

How can i test the Pressure switch for the compressor? can i short out the connector to make it think its on?

 

thanks

[Biotex]

Yes, touching the two wires together will bypass it. A better way is to ohm out the switch. You need to unplug the low pressure switch to test it.  If you have sufficient pressure to close the contacts, then you will read continuity between the two wires.  Are you sure the can and a half is enough to give you sufficient pressure to trip the switch?

[Blue88Comanche]

I need to look up the capacities for the r134a but the guy that was with me was saying usually 18oz is should get it going

[Biotex]

I need to look up the capacities for the r134a but the guy that was with me was saying usually 18oz is should get it going

I would agree also.

[ftpiercecracker1]

I just had my a/c system recharged the other day. With it completely and utterly empty, I used 2 12oz cans, for a total of 24oz. Pressures seem to be a tad low on the low side, but my compressor still kicks on and my a/c is decently cold. I have been told that when switching over to R134a you can only use 75% of the original R12 capacity. For our trucks it was 32oz of R12 in 1989, 75% of 32 is 24.

 

I would start by doing a proper evacuation then recharge it with the right compressor oil and 24oz of R134a.

 

 

 

EDIT: with your a/c set on max, check for 12v at the pressure switch.

[Blue88Comanche]

So 2 1/4 lbs or 3 12oz is what i found. I also found the leak, its the pressure switch. That also explains why I never could get the system to start. I also Jumped the connector to test the system is seems to be working thus far. but i have a HUGE leak.

[Blue88Comanche]

I just had my a/c system recharged the other day. With it completely and utterly empty, I used 2 12oz cans, for a total of 24oz. Pressures seem to be a tad low on the low side, but my compressor still kicks on and my a/c is decently cold. I have been told that when switching over to R134a you can only use 75% of the original R12 capacity. For our trucks it was 32oz of R12 in 1989, 75% of 32 is 24.

 

I would start by doing a proper evacuation then recharge it with the right compressor oil and 24oz of R134a.

 

 

 

EDIT: also check for 12v at the pressure switch.

 

I must have been writing my reply the same time as you.. I knew there was a pressure difference but not a capacticy difference

[Blue88Comanche]

edit having internet issues

[ftpiercecracker1]

 

I just had my a/c system recharged the other day. With it completely and utterly empty, I used 2 12oz cans, for a total of 24oz. Pressures seem to be a tad low on the low side, but my compressor still kicks on and my a/c is decently cold. I have been told that when switching over to R134a you can only use 75% of the original R12 capacity. For our trucks it was 32oz of R12 in 1989, 75% of 32 is 24.

 

I would start by doing a proper evacuation then recharge it with the right compressor oil and 24oz of R134a.

 

 

 

EDIT: also check for 12v at the pressure switch.

 

I must have been writing my reply the same time as you.. I knew there was a pressure difference but not a capacticy difference

 

 

don't quote me on the capacity difference, it is just what i was told by my parts guys. I do trust him and he is knowledgeable, its just that he has been off in the past. Remember that to little freon/pressure will only result in poor cooling, but to much pressure and you really F your system up.

 

I would definately start with 2 cans and if the pressure still seems off or your cooling just isnt quite there i would add more, how much depends on current ampient temperature. The best conditions to do this would be around 72 F*, and clear skies. Barometric pressure and all that.

 

With everything said, i will probably be adding a little to mine. I just don't think its quite there yet.

 

 

P.S.

 

With the fan on high its only cold for about 15-20min then it slowly becomes just ambient temp. It will cool back down if i put the fan on low and leave it for a little bit. I have stuck a digital thermometer in the vent duct, fan on lowest speed, a/c on max and the lowest it will go is 50*F  :dunno:

 

 

 

 

EDIT: If your system is TOTALLY emptied, don't forget to add oil, between 6 and 7 ounces. It is CRITICAL your a/c system has not only the right amount of oil, but also the appropriate type of oil.

[Biotex]

I don't believe the capacity difference when switching to R134a. There might be a small weight difference between the two freons, but not 25%.

 

The system is fully charged when the evaporator is flooded, so if a sight glass is present in the system, once the bubbles clear up, it is an indication that the evap. is flooded, and so adding more Freon does not add to the cooling.

[dasbulliwagen]

After converting mine I needed to add closer to 3 pounds to get it to work properly and have correct pressures.

[Blue88Comanche]

EDIT: If your system is TOTALLY emptied, don't forget to add oil, between 6 and 7 ounces. It is CRITICAL your a/c system has not only the right amount of oil, but also the appropriate type of oil.

 

my main goal was to find the Leak.. It should be empty by the morning.. then replace the drier and then add oil and Freon 

[ftpiercecracker1]

I don't believe the capacity difference when switching to R134a. There might be a small weight difference between the two freons, but not 25%.

 

The system is fully charged when the evaporator is flooded, so if a sight glass is present in the system, once the bubbles clear up, it is an indication that the evap. is flooded, and so adding more Freon does not add to the cooling.

 

 

I agree. My new drier has a sight glass like you stated. Do you think it would be possible to "top off" my system using one of the DIY cans they sell at the auto parts store? If so how could i do this?   

[Biotex]

 

I don't believe the capacity difference when switching to R134a. There might be a small weight difference between the two freons, but not 25%.

 

The system is fully charged when the evaporator is flooded, so if a sight glass is present in the system, once the bubbles clear up, it is an indication that the evap. is flooded, and so adding more Freon does not add to the cooling.

 

 

I agree. My new drier has a sight glass like you stated. Do you think it would be possible to "top off" my system using one of the DIY cans they sell at the auto parts store? If so how could i do this?   

Look at your sight glass with the A/C on, fan on high, a warm day (70° + or so will do). If there are bubbles, then you can safely add more Freon. Get a can, and you will need the hose for the low (suction side). The Freon in the can is at a higher pressure than the Freon in the suction line (with the A/C running), so it will pull from the can. With the can right side up, gas will enter the system, with the can upside down, liquid Freon will enter.

Upside down will empty the can quite fast, but you need to be careful and alternate between the two because you don't want to allow liquid to enter the compressor. Remember how liquid is non compressible? It can lock up a compressor. Usually not an issue with the rotary style compressors on comanches, but don't push your luck, just go slow...

 

You should get rid of 95% of all bubbles, and be good to go.

 

If you have a temperature gun, you can easily tell when the evaporator gets flooded. The suction line just before the compressor will drop in temperature drastically when the liquid starts reaching that point. You can actually feel the difference with your hand, it is something like a 10° or 20° drop.

Hope this helps.

[Biotex]

 

EDIT: If your system is TOTALLY emptied, don't forget to add oil, between 6 and 7 ounces. It is CRITICAL your a/c system has not only the right amount of oil, but also the appropriate type of oil.

 

my main goal was to find the Leak.. It should be empty by the morning.. then replace the drier and then add oil and Freon 

Be advised that you can add too much oil and damage the compressor. Oil and Freon mix together somewhat, that is why when there is a leak, it gets dirty around the area. This is also how the internal parts get oiled to a point. There is also oil in the compressor and receiver that doesn't completely empty out from a leak, so if you keep adding oil every time you add Freon, you can easily have too much. This isn't usually as much a problem with the rotary style compressors as it is with the York style piston types, because they had a large sump just for oil similar to your air compressors in your house.

[Blue88Comanche]

What dryer did you get and where from? I would need to replace mine and I don't think it has the glass sight you are talking about.