XR 4000 No AC power

[Dandolore]

XR 4040 No AC power. I've replaced the A/C compressor due to a short on the a/c clutch. I've replaced Air Con resistor, Blower fan relay, and A/C control board. The light indicator on the A/C panel is not coming on or the LEDs. Fans are not blowing either. A/C has 0 power. I've checked the fuses and there is power at the fuse panel inside the cab. I've checked the grounds on the tractor. I cannot find my source of power issue. Any advice?

 

[alexpops]

No power where? to the clutch? to the blower? When you replaced the compressor, did you evacuate the A/C lines & hook up the manifold gauges to add freon/oil? (I'm assuming you don't have a recovery machine) Did the compressor come pre-oiled, or did it tell you how much to add before install? If pre-filled, did you run it through the gymnastics to lube the seals? (usually set it on its nose for a minute or two, then rotate it through 360 in both axes once or twice slowly) How long was the system open? did you replace the dryer as well? What is your static pressure in the A/C lines? (not running/engine off/low & high sides should be about the same. Temps when you tried to get her going? We've had colder temps than usual in East Central FL so that might be part of it usually those things won't kick on below 58-60 degrees. Assuming you get a decent day in the 70's/80's, I'd draw a vacuum of 28-30 inches (as much as your pump will draw) for at least 45 minutes then close the manifold valves & see if the vacuum holds for an hour. If no, track down your leak. If yes, start her up turn on the A/C & start slowly adding the freon needed to the low side only (specs should be in the shop manual), check your pressures & see when/if the compressor kicks on. It'll cycle on & off depending on the pressure difference & you need to see when it does. Not sure if it's an orifice tube or expansion valve system but goofy pressure readings could indicate a problem there (usually a plugged orifice tube from moisture contamination in the system if open for too long). You need some pressure or the safety override will not let the compressor start. You can try jumping the safety switch to see if that gets power to the clutch, but don't run it that way or you could destroy the compressor. min pressure should let the compressor start up if there is 15-20 psi static If you don't kick-on by 25psi or so, the pressure sensor safety switch could be bad. The manual will have temp/pressure charts for actual operation & usually a diagnostic tree chart for areas to explore.

 

[Tinhack]

Ditto what Alex says. Instead of throwing parts at it, buy a meter or test light and follow the flow through the diagram. Most tractor systems use an expansion valve and easily clogged if you had a compressor failure. The expansion valve should be up on the evaporator (inside the cab).

 

[Dandolore]

Update. So the parts I replaced were because I was already there and had access to it. The original problem was A/C just shorted and failed due to the A/C wiring running form the A/C clutch rubbing on the compressor. Its been a 4 month project on and off. But I did replace the A/C nob controller due to mixing up the A/C temperature gauge selector and the fan speed selector nob. When I original did that there was a audible popping sound and everything cut off A/C wise. So I'm leaning towards a short in the wiring harness. Anyone deal with something similar before? I never repaired a wiring harness. Also I'm not sure if there is another point of failure area I should be looking at besides the a/c wire harness itself.

 

[alexpops]

Sounds like wires were hooked up wrong when you screwed up the switches & you created a short. The popping sound was a relay, fuse, or resistor going ... no way to tell which without seeing the wire diagram and knowing which wires you connected to the wrong switch.

Best approach (IMO) would be to get the wire diagram and specs on each component from the shop manual. Using a multimeter, first, trace power from battery/keyed hot through the circuit. That'll tell you if a switch, relay, fuse, fusible link is fried. A test light will tell you if power is getting there, but the MM will also give you the voltage (drop), which might help find corroded connectors. Then, check internal resistance on the components and connections against specs to see what else you may have damaged/burnt (fan resistors).

As far as chafed wires/harness shorts, etc. ... trace the wires. If you were working, you could jiggle the harness at various spots to narrow down the area to open based on being able to shut it off by moving the wires. A powerprobe might help narrow the direction of search. But not useful unless you get over the learning curve or you could create shorts with it.

Don't open the harness until you are positive that you are/are not getting power to ( and through) the components that need it -- switches, relays, fan motor, etc. If you have power, disappear between two components (hot at switch out, but nothing at relay in or hot at relay in/nothing at relay out) the short is in that segment of wire or that component.

Double check ALL your fuses for continuity before starting, AND make sure all your switches are wired correctly, or you'll never figure it out since you'll be reshorting every time you apply power.

It's always a good idea to fix one thing at a time, then decide if you need to do more. Start simple (cheap) and work toward complicated (expensive). Throwing parts at a problem is usually an act of desperation, and if the fuses are working as intended, the parts may be fine, even with a short. Finally, once you have it fixed, a bit of dielectric grease on your connections goes a long way to avoiding corrosion related voltage drop problems in the future.

When you are sure that you have power going where it needs to, you still need to evacuate and recharge your a/c lines to get it to cool, since you opened things up when you replaced the compressor. Evacuating is vital to get the moisture out, or you'll be doing this again in July.

Good luck.