Electricians and AC experts get in this thread

I have a 4640 on which the air conditioning works only sporadically. When it is not working, the clutch will cycle on and off every couple of seconds.
The compressor was replaced with a Sanden a couple of years ago, along with the dryer and exp valve. The dryer and exp valve were replaced again last spring.
Here's where it gets interesting-last year when and this spring when you adjusted the temp, the radio would go black for a second or two. Thinking that I have an electrical problem, I replaced the temp control and cleaned up a bunch of wiring and grounds up there. I also replaced the cab relay and the circuit breaker that goes to the radio and temp control. While I was at it I added what is called a clutch saver kit. Basically a relay that takes power from the positive stud on the starter and sends it to the clutch. Now that yellow wire that goes down from the cab across the engine to infant of the radiator and back to the clutch only serves to close the relay.I also added a new ground wire from the tractor frame to the Sound Gard.
There has been little change, except that now when you change the temp, the radio only darkens for a fraction of a second.
When the AC decides to work, maybe, possibly, sort of has something to do with if you have the sprayer monitor on, but not always.
I am tempted to run a new hot wire from the relay/circuit breaker area under the cowl up the window seam and directly to the temp control, thinking somewhere there seems to be an interruption in electrical flow.
Anyone have any other ideas?

I obviously meant "in front" of the radiator. Not "infant". No babies were harmed in working on my AC.

I would run the new wire from the cold switch to the AC compressor, there are places where it can go bad, I run them down the left side of the cab, there is nothing in the way there,then under the cab,in behind the battery and past the starter..this will eliminate that possible bad spot, also re-check your breakers, a lot of times they will loosen a bit and rust will make a bad connection,,a weak connection will make heat and cause the breaker to heat up and kick out, a new nut and star washer makes that better,,this "could" cause weak currant to the cab and then when you ask for more power to run the AC or sprayer control it robs power to the radio..It's AC season so we need to sort out these potential problems now..

I just finished up a 4440 that had several issues, one of them being wiring.....those harnesses are getting pretty tired
and like Tim says every less than perfect connection adds up to more resistance in the circuit. I like Tims idea to run
a new wire. The correct police might not like it but you will be comfy.
We sure don t need any air conditioning up here today!
BTW 4430 looks really good!

As previously stated. Do not trust any chassis return path or connection back to the battery (-) post.

Sounds like to me you need a new clutch coil. The one you have is intermittent. Hang a test light on the clutch coil and see if the power is going off and on with your compressor first off. Chances are good you have solid power and the coil is doing that cycling on it's own.

I have experienced connection problems with the bulkhead in front of the cab on mine. Could be your culprit too. Like said, a new wire to bypass all of that may be needed.

Well, from your description, here is what we know; that the compressor cycles and that the radio darkens when you adjust the temp.

What we don't know, is the clutch losing power when the compressor cycles? This is the place to start because then we can determine whether it is the clutch or something else. Another piece of information that would be nice, are the compressor and alternator driven by the same belt? It is possible that if you are cycling on high pressure that the extra load on the compressor when it kicks in might be affecting the alternator output momentarily. If that is the case, your problem would be refrigeration/mechanical in nature and not electrical. But again, this all depends on whether or not the power is being cycled to the clutch.

The compressor uses a different belt, and the compressor wire could be unplugged to isolate the clutch,but I still think it's a bad power supply or a short in the wire to the compressor..

I had thought about running a new yellow wire more direct from the temp control to the clutch. The temp control just gets a switched hot to one terminal then the wire to the clutch from the other terminal, right?

If it was the clutch coil, wouldn't it just go out and not cycle repeatedly?

Check out A-P Air part# 220-045 "clutch saver kit", or get a relay and harness from local Napa and check you tube as to wiring diagram. Relay in compressor circuit makes up for 40 yr old tractor wiring harness issues

Yes, the cold switch gets power from the fan switch on one spade, and on the other spade it goes to the compressor,, the yellow wire goes down the right post through a connector under the cab behind the battery, then up the fire wall,,out to the top of the front of the radiator, then down and for some reason they get wedged in with the 2 pipes clamped under the left of the radiator then to the compressor,,where the wedge in with the pipes is always a place to short out,,the plug behind the battery is another problem area,,skip all that and run a new wire down the left cab corner,,around behind the left battery,,up past the stater and to the compressor..

(quoted from post at 16:15:09 05/07/17) Check out A-P Air part# 220-045 "clutch saver kit", or get a relay and harness from local Napa and check you tube as to wiring diagram. Relay in compressor circuit makes up for 40 yr old tractor wiring harness issues

Click to expand...

Already added as I wrote in my original post.