Agpopp Posted June 8, 2023 Share Posted June 8, 2023 Dash air on this new to me did work for a short time. PO gave me all the bills and in August of 20 had the entire system rebuilt- new compressor, dryer, TXV, and some lines. Working on troubleshooting yesterday, have plenty of static pressure, so I jumped the low pressure switch to see if I could make the compressor start. I heard the relay in the front box click, then click and click. Relay felt hot to the touch. Pulled up the closet floor and I disconnected the connection for the compressor, and immediately the condenser fan in the side compartment began to run....I've never heard it run before. So using my meter, I found power and ground in the connection and hooked it back up, killing the condenser fan. Got some jumper wires and swapped the polarity of the connection to the compressor just for a test and wow did those alligator clips get hot in a hurry! So bottom line is I conclude the less than 3 years old Sanden 4306 compressor is shorted internally? Is it junk? Anyone with another opinion? PO spent thousands on this repair, so I feel it's worth poking around, otherwise I'd just rely on the roof air. 1 Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted June 8, 2023 Share Posted June 8, 2023 It's probably a short at the compressor clutch, not actually inside the compressor. I would be concerned why a fuse didn't blow> Link to comment Share on other sites More sharing options...
Agpopp Posted June 8, 2023 Author Share Posted June 8, 2023 5 minutes ago, Ray Davis said: It's probably a short at the compressor clutch, not actually inside the compressor. I would be concerned why a fuse didn't blow> Good question Ray, in the front road box there is a 20 amp breaker installed instead of a fuse. I've never seen one like it, but it's doing its job. 20230607_115620.mp4 Link to comment Share on other sites More sharing options...
Tom Wallis Posted June 8, 2023 Share Posted June 8, 2023 I would agree with Ray. It sounds like you just neet a compressor clutch. They sell breakers that will replace a fuse and sometimes we someone keeps blowing a fuse they will replace it with one of those breakers. I bet they were having trouble with the clutch before you bought it. A compressor clutch isn't that big of a deal to replace if you can get at it easily. 1 Link to comment Share on other sites More sharing options...
Agpopp Posted June 8, 2023 Author Share Posted June 8, 2023 3 minutes ago, Tom Wallis said: I would agree with Ray. It sounds like you just neet a compressor clutch. They sell breakers that will replace a fuse and sometimes we someone keeps blowing a fuse they will replace it with one of those breakers. I bet they were having trouble with the clutch before you bought it. A compressor clutch isn't that big of a deal to replace if you can get at it easily. I can get at it, but doubt I can do it on the motor. Probably have to evacuate and recharge to R and R it. Link to comment Share on other sites More sharing options...
Tom Wallis Posted June 8, 2023 Share Posted June 8, 2023 That's an option but it's usually less work to do it on the engine and it doesn't require evacuation and recharging. 4 Link to comment Share on other sites More sharing options...
Ivylog Posted June 8, 2023 Share Posted June 8, 2023 3 hours ago, Agpopp said: Good question Ray, in the front road box there is a 20 amp breaker installed instead of a fuse. I've never seen one like it, but it's doing its job. 20230607_115620.mp4 Auto resetting fuse. The clutch can be replaced. 1 1 Link to comment Share on other sites More sharing options...
Robert U Posted June 8, 2023 Share Posted June 8, 2023 I had a similar problem where compressor would try to start but condenser fan was sluggish . Its motor was stiff. This caused the circuit breaker that feeds both compressor and condenser motor to trip. the circuit breaker would reset itself and try again to start both. Replaced condenser fan and all was well. Bought fan at NAPA. Bob U 2000 Dip The clutch on compressor will have a very small amount of resistance. probably less than 10 ohms. Bob U 2000 Dip Link to comment Share on other sites More sharing options...
Agpopp Posted June 8, 2023 Author Share Posted June 8, 2023 54 minutes ago, Robert U said: I had a similar problem where compressor would try to start but condenser fan was sluggish . Its motor was stiff. This caused the circuit breaker that feeds both compressor and condenser motor to trip. the circuit breaker would reset itself and try again to start both. Replaced condenser fan and all was well. Bought fan at NAPA. Bob U 2000 Dip The clutch on compressor will have a very small amount of resistance. probably less than 10 ohms. Bob U 2000 Dip That's a thought. I'll disco the fan and rehook the compressor to see what happens. Though it was running and sounded smooth. Link to comment Share on other sites More sharing options...
Rikadoo Posted June 9, 2023 Share Posted June 9, 2023 So on Ford AC you can buy an replace pieces individually or all together. It sounds like the field coil is the culpret, i would recomend replacing all 3 pieces field coil, pully, and the clutch. Only cause if there was a update to one or all three pieces it may not be a good fit with your oldder unit. Before going any further i would first verify your compressor is not locked up. To do this WITH THE ENGINE OFF try turning the clutch “center of the 3 pieces” several rotations in the direction it normally turns, if it fails to rotate then its possable its locked up, which is a whole nother story. So if it does rotate then i would continue on getting the 3 Amigos as stated above, having rebuild several Ford compressors while your getting the parts you might also order if available a shim kit for the clutch, as not all clutches are alike, an that the “air gap” will need setting (which you can measure the old one before you disassemble or research the spec) and adjust the new set accordingly. It goes without saying to little airgap an the compressor will run without electrical input an too wide a gap it will never engauge with electrical input. 1 Link to comment Share on other sites More sharing options...
Happycarz Posted June 9, 2023 Share Posted June 9, 2023 If the compressor A/C lines are long enough and flexible enough, you might be able to unbolt the compressor and move it a bit to give you better access to the clutch assembly. That would save you from having to evacuate it and recharge it. First things first is to determine that it is the compressor clutch. 1 Link to comment Share on other sites More sharing options...
dl_racing427 Posted June 9, 2023 Share Posted June 9, 2023 I second the recommendations that the clutch field coil is shorted. I'd definitely replace it without disconnecting the lines. If it's really tight, you could even unbolt the compressor and move it for better access with the refrigerant lines still attached. A quick check for a seized compressor is a good idea, as a slipping clutch could have overheated the coil, but I think that's unlikely. You can probably rotate it by hand. It will have some resistance, but should rotate smoothly. Good luck. Link to comment Share on other sites More sharing options...
Happycarz Posted June 9, 2023 Share Posted June 9, 2023 To verify it is not the compressor itself, grab the outermost plate of the compressor/clutch assembly to verify the compressor is turning smoothly. If one of your other vehicle has a compressor easily accessible, see what that one feels like for a comparison. Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted June 9, 2023 Share Posted June 9, 2023 23 hours ago, Agpopp said: That's a thought. I'll disco the fan and rehook the compressor to see what happens. Though it was running and sounded smooth. That's a good & easy thing to try. I would try it. As others have stated you may be able to take all of the compressor mounting bolts out and rotate the compressor enough to get at the clutch. Use a strong light and mirror to make certain a wire is not shorted up close to the clutch. Link to comment Share on other sites More sharing options...
Agpopp Posted June 9, 2023 Author Share Posted June 9, 2023 4 hours ago, Happycarz said: To verify it is not the compressor itself, grab the outermost plate of the compressor/clutch assembly to verify the compressor is turning smoothly. If one of your other vehicle has a compressor easily accessible, see what that one feels like for a comparison. It spins free, first thing I did. Link to comment Share on other sites More sharing options...
Gweedo Posted June 10, 2023 Share Posted June 10, 2023 Mine kept blowing the fuse. they replaced the compressor, the fuse kept blowing. the short was in the condenser fan motor. replaced fan nor more problems with the fuse 1 Link to comment Share on other sites More sharing options...
Agpopp Posted June 14, 2023 Author Share Posted June 14, 2023 Tried to disconnect the condenser fan and hook up compressor but still same result. Guess I'll be on the phone looking for a clutch. I'll post back when I have a solution. Link to comment Share on other sites More sharing options...
Agpopp Posted June 15, 2023 Author Share Posted June 15, 2023 Talked to a guy today from ACparts.com in Texas. Very knowledgeable and was willing to help. Said he doesn't see many with a dead short but it does happen. I explained to him the the 2 pin connector on my coach has 12v and ground switched as compared to the AC compressor plug. So essentially I'm feeding 12v into the black wire and ground to the red. He thought that the diode certainly would be cooked and causing the short being hooked up backwards. He did have the field coil available for around 50 bucks, but watching some vids, seems to be a joh that will prove difficult through the closet floor. Would anyone with a Neptune / Cayman be willing to check out the connector and polarity situation on thier coach? See what's really going on here. Link to comment Share on other sites More sharing options...
Happycarz Posted June 15, 2023 Share Posted June 15, 2023 Both wires are insulated to and from the coil. The coil doesn’t care which way the current flows, so the colors don’t matter. From what you said previously, it sounds like the coil is fried. Did you take an ohm reading at the ends of the pigtail were it connects to the harness? Of course with it in plugged, that is. The take an ohm reading from each of the wires to ground, or compress case. It should be infinity. If it is zero, it is shorted to ground and the new coil will fix it. Link to comment Share on other sites More sharing options...
Agpopp Posted June 15, 2023 Author Share Posted June 15, 2023 Yes, ohms are .01 so it is shorted, but I don't want to short the next one, so that's why the polarity matters. We suspect the diode is what is shorted to ground and the diode won't work if the polarity is wrong and will eventually kill the coil, as most likely what I have now. Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted June 15, 2023 Share Posted June 15, 2023 So he says there is a diode inside? I never knew that, what purpose do you suppose it serves? Link to comment Share on other sites More sharing options...
Ivan K Posted June 15, 2023 Share Posted June 15, 2023 Where is the diode(s) that you mention and what is it for in a clutch circuit? Link to comment Share on other sites More sharing options...
Happycarz Posted June 15, 2023 Share Posted June 15, 2023 General Motors 30-40 years ago put a diode across the wires of the A/C coil. When the power to the coil is removed, a high voltage spike occurs and the diode clamps it to ground, protecting everything upstream on that circuit. Link to comment Share on other sites More sharing options...
Agpopp Posted June 15, 2023 Author Share Posted June 15, 2023 Called a flyback diode, spikes can be up to 50v when the clutch kicks off. Here's the 4306 schematic. Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted June 15, 2023 Share Posted June 15, 2023 9 hours ago, Happycarz said: General Motors 30-40 years ago put a diode across the wires of the A/C coil. When the power to the coil is removed, a high voltage spike occurs and the diode clamps it to ground, protecting everything upstream on that circuit. 9 hours ago, Agpopp said: Called a flyback diode, spikes can be up to 50v when the clutch kicks off. Thanks guys, I assumed as much but I'm trying not to assume things. Link to comment Share on other sites More sharing options...
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