Blowing the Heater/AC fuse

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Well-known member
Apr 25, 2006
When I bought my motorhome the previous owner said it did this.  I found a couple of vaccum lines d/c'ed under the dash to the controler and it worked fine for two trips.  On the way back from a week long trip it blew the fuse with the ac on, multiple times.  The weird thing is that it doesn't blow it right away, it takes about 3-5 minutes and may blow faster with higher engine rpm's, but I not sure about that.  The previous owner thought maybe the motor had a short and changed it but it didn't fix it.  I'm thinking there is a short in the wiring somerwere.  Has anyone had a issue like this or have a quick, silver bullet fix for it?  Its a 92 27 foot Itasca Sunrise. thats alot. Jason
Thats always possible, and what we did but I would like to fix the problem and have the ability to defrost the windshield. thanks
I found a couple of vaccum lines d/c'ed under the dash to the controler and it worked fine for two trips.
Not sure what you mean by "d/c'ed" - Direct connected, disconnected? Which lines? Coming from where - air control doors? Which fuse blows? Does the compressor cycle very rapidly (several times/minute)? Do you see any user-added wiring to the fuse block? Could be partially shorted compressor clutch.
Sorry, D/C'ed = disconnected.  It was allowing the defrost vents and heater vents to stay on at the same time.
The 35 amp fuse labeled "Heater" blows.  The compressor and blower fan do not work.  No other circuits are effected that I can tell.  All other fuses are good.  It doesn't look like any added wires.  It worked all the way to the camp site but started blowing on the return and when it was hot.  I can defietly go with the generator idea and probably will till I get it fixed but not having it works bugs me.

Quite honestly, I've NEVER heard of a 35 amp fuse in any automotive circuit. I suspect someone has added something to the circuit that required that fuse size. Is thatlabel a manufacturers label, or some thing that was added? The heater blower might require 5-10 amps maximum, and the compressor clutch maybe another 5 to 10 - certainly not anything near 35 amps! I think you may need to find whatever else is drawing current from that particular circuit. What else are you running when the fuse blows?
It maybe a 30 amp.  The label says it should have a 25amp.  The compressor and fan motor circuit run off of the same fuse.  I wasn't running anything else.  I tried to keep the motor (fan) on low and it still blew it after a minute or so.  I haven't followed the wiring yet but it is going to be a pain to get behind the fuse panel. It is behind the grill hatch.  I'm not sure were the fan is yet.
Try disconnecting the clutch and run the a/c as if it were connected. There should be a single wire connector very near the compressor that pulls apart. If it doesn't blow then, you probably have a bad clutch. Not definitely, but that would be my guess.
I have been messing with this while dealing with my other problem you have been helping me with.  Today I checked the fuse and it is suppose to be a 25amp.  I put one in and ran it in the driveway while messing with the timing.  It ran fine.  Right when I got it out on the road it blew.  Came back and put in a 20amp (its all I have) ran it in the driveway for about 20 minutes turning it up/down, on/off over and over, moved the wiring harnesses around, disconnected the compressor and reconnected it and reved up the motor.  It would not blow.  I took the cover off of the blower motor.  It seemed to be running fine but the motor casing was hot to the touch.  I pulled off the vent tube to it and all seemed to be working ok but it had little to no air flowing from the blower housing to the motor case.  The motor is new and was replaced by the previous owner.  A couple of questions.  Is it possible the check the electrical function of the clutch?  If it is bad is it possible the change out the clutch without having the discharge the A/C system, its R12.  Are these motors suppose to get hot?  Its not red hot, doesn't smell hot but it is hot to the touch with only running for a couple of minutes.  I guess its possible to have a bad new motor,  I had a bad new distributor cap!! thanks
Yes, you can replace the clutch without losing refrigerant, but you'll need a gear/pulley puller to do it. Some parts stores may let you borrow or rent one. The motor will get fairly warm, but should not be hot after just a few minutes of running. Most have bronze bearings that you can lubricate, but getting at them can be quite a job. Good luck! :) (and practice up on your swear words)
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