A/C Compressor Won't Kick On

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pastortom1

pastortom1

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I've got the system ready to charge with 134a, and I can't get the compressor to kick on..........The wire from the compressor hecks out as far as I can get to the edge of the firewall......no problems........

Fuse is OK, BUT in my wiring diagram, I note that the heater runs off the same fuse....AND, there is an inline resistor for the heater.......

Question: Does the A/C compressor use a resistor also?........or does it run off straight 12V dc?................If it runs off straight 12V, I could rig a switch for now until I can tear the dash apart and do it correctly.......don't want to blow anything though......I don't see any sort of relay in the diagram either.

Can that compressor be wired directly to a heavy duty switch for now or not?

Need a fast answer.....if you can shed light, point it this way! :read2:
 
Now we're totally confused..............

The dash actuators for the heat and a/c venting is supposed to be vacuum operated................correct?.................sure looks so.

Problem is that we can locate only ONE vacuum inlet/outlet anywhere on the firewall that could possibly feed the dash system...........there are 2 small lines coming out of one good sized molded grommet.......BOTH of these lines are hooked up to a small black plastic canister on top of the fender well of the passenger side.........BUT, the lines are both the same size, and the inlets of the canister are NOT......one is slightly larger than the other......and the screwy thing is that they don't even look like they are made to snap a line onto............I've asked, and can't seem to find anyone who knows exactly WHAT the canister IS.

If I don't get vacuum to the dash system, my selectors for a/c and the like won't work anything..........this is probably why there's no juice for the compressor...........no?

We can find NO OTHER vacuum lines going into the drivers compartment.......NONE.........these 2 lines MUST do something.........

After we bought the car and detailed the engine bay, we hooked up those lines exactly as they came out............BUT, the previous owner could have screwed it up........................

WHAT IS THE CANISTER (it is NOT the a/c dryer I'm talking about.....I'm not that confused, yet)...........
........and WHERE do the 2 small vacuum lines go? Are they the ones that run the dash controls??

and if NOT, then WHERE is the other feeder line?????????????????

HE-EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE-LP! :blob6:
 
Check this out........I think the canister has something to do with the emissions baloney........

BOTH of the vacuum lines from the firewall go into the can........this makes absolutely NO SENSE to me....................

My dash needs vacuum.........if someone has the know how, let us know how.

:happy6: :happy6: :happy6:

Can.jpg
 
The canister looks to be a vaccum canister. The way I would think that the lines should go is one vaccume line to a vaccum sorce and the other to the vaccum controls for the A/C. I'm not sure where the second vaccum hose would go from the firewall unless there is another vaccum dashpot somewhere. Bear in mind that I'm talking on what it looks like. I may be totally off base.
 
A line goes from the manifold to the vaccum canister. One of the lines from the firewall goes from the vaccum canister and the other line from the firewall goes to a vacuum heater valve on your heater hose. I do not know which hose is which on your car but if the two hoses are different sizes the bigger of the two is the feed line from the vacuum canister and the smaller of the two goes to the heater control valve.

Chuck
 
Yeah, on my 68 Barracuda there are two vacuum lines that come out of the firewall, one goes to vacuum, one goes to the heater shut off valve that looks something like this.

H1949.jpg
 
There should be a low pressre switch somewhere in your system that would keep the compressor from turning on if there is no refrigerant in the lines. I don't think the vacuum lines have anything to do with the compressor turning on, they are more for control of the dampers/heater valve. The low pressure switch should be mounted on the dryer or in the line from the evaporator to the compressor. At least this is what I am familiar with from older mopars.
 
If his is the case, HOW do you get the new refrigerant into the system?..........Unless I'm missing something, the compressor needs to be on in order for there to be suction at the low pressure side for a recharge...............????

Sounds like a catch-22...................... :read2:
 
Is the system vacuumed down? If not that needs to be done. Check for vac loss to see if you have a leak.

AC wise the typical thing is to jump wire the pressure switch plug. This will kick the compressor clutch in. Alternatively if the compressor has a plug on the wiring close to it you can unplug it and jumper a hot wire to it to get the clutch to kick in. Not a permanent thing. Just to get a bit of the 134 in. The system should, once hooked up normally, start cycling the clutch in and out as you continue to fill with eventually staying pretty much on.

Watch your gauges! Be sure to follow the instructions on the gauge readings precisely. Will tell you if there is a blockage etc. and also make sure that you don't have a pressure issue. Too much is just as bad as too little in the system.
 
I am no way a/c knowledgeable, but I think MoparBrit has the idea. The ones I've done will take in enough freon for the compressor to start once they have been vacuumed down & have no leaks. You just have to hook up the can to the gauges & give it a little time. I never had to jump the low pressure switch to get freon to go in the system.
 
There is enough residual pressure in the freon can to trip the low pressure switch. Just start filling the system and the compressor will kick on when it has enough pressure. You don't need to jumper anything to make it run if everything is hooked up or working correctly.

Chuck
 
We fixed the vacuum problem, just as stated in a preceeding post........dash works a-ok now..........BUT, the compressor did not cycle at all in a/c mode.

I hot wired the compressor, and it worked fine.......I cycled it a bit, then hooked up a 134a can and gauge...........after discovering an inlet valve problem and fixing it, I did it again...........cycled through a half can...........just a half can.........and the pressure read at the max of the blue zone (safe zone)............If I put in any more, it will go into the yellow and red...............there is not enough coolant in there to really do much good.........I could feel a "wee bit" now and then during the test.

OK................we have not enough coolant in the system, and too much pressure if we try to put in more...........

What now?......................Any A/C men out there???

By the way, if we hook the pressure switch back up the way it was, the compressor still will not cycle on it's own............does this switch activate the cycling?...............or is it something else?

:blob6:
 
exactly.

340mopar said:
There is enough residual pressure in the freon can to trip the low pressure switch. Just start filling the system and the compressor will kick on when it has enough pressure. You don't need to jumper anything to make it run if everything is hooked up or working correctly.

Chuck
Click to expand...
 
Did you pull a vaccum on the system as stated in an earlier post by MoparBrit? If not, you won't be able to put anymore coolant in the system.
 
I guess that's what we may be up against...........(?)...........

How much dough do you suppose it's going to cost to have the system sucked out and recharged properly? :|
 
If I remember correctly we used to charge an hours worth of labor, which equated to about 70 to 80 bucks. Depends on the labor rate and how well you know the technician.
 
don't by pass the system with an on off switch for the compressor. If your system hits too high of a pressure it needs to cut in the fun/or cut out and if it high too low of a pressure it needs to cut out as well if not you'll be buying a new compressor. I am not sure exactly how this system is run. However almost every system i have run across has a low pressure switch that prevents the clutch from engaging. Check for power and grounds at this switch. If you can engage the clutch by jumping the connector then the switch is most likely faulty. The high pressure switch is there to kick and electric fan in..providing the car has an electric can. Fan forces air through the condenser in an effort to reduce pressures in the system (cooling the R134A). Check for leaks with Nitrogen............it is clean and dry so no contaminates are introduced to the system. 300 lbs is what i regulate the bottle to while testing....then just soap and water at every connection. The hardest leak to find is the seal right at the shaft of the compressor cause the clutch is in the way. ummm....if you have gauges hooked...a good rule of thumb is the high side pressure should be running at two time ambient temperature plus or minus 10%. once you have a proper charge in.
A wiring diagram would assist you tonnes while chasing power and ground for the a/c. To charge the system you need a vacuum pump which needs to run for a minimum of 15 minutes............once thats complete you can add refrigerant oil (1 to 2 ounces) the vacumm draws the oil in. Then charge. I don't recommend using Redteck or propane. R134A is the best to use providing the system was designed for it.........older cars usually have R12 which can be easily retrofitted to R134A. I don't know how much help my knowledge of A/C is gonna be for you with your problem, but i hope it helps you find some solution.
 
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