AC Fan Stopped Working

[SuiteSuccess]

Got home yesterday from trip and noticed AC fan not working.  Didn’t have time to troubleshoot but will soon.  My first thought is blown fuse but what else should I consider?

[TXiceman]

Presume this is your RV.  Was the breaker tripped, was the compressor running?  Fan motors and capacitors do go out.

Let us know what brand A/C you have,

 

Ken

[ARGO]

Mine stopped (Dometic reverse cycle). Could hear the compressor running/stopped/running but no cooling. Inside fan working. Wasp nest blocking the circ fan on the rooftop unit....................................

[SuiteSuccess]

Sorry, not enough information provided by me.  This is the fan in my truck.  2006 Volvo 780.  My bad.

[Brad & Jacolyn]

Long shot but I had a plug by the AC compressor under the hood that would get kicked loose when I climbed up on the frame to wash the windshield. Rerouted wire slightly and took it out of the way.

[dennisvr]

1 hour ago, SuiteSuccess said:

Sorry, not enough information provided by me.  This is the fan in my truck.  2006 Volvo 780.  My bad.

Don't know about a 2006, but I worked on a late 90s Volvo that the fan wouldn't work.  Fuse was good, so I tested for power at the motor and had it there.  Determined that the fan motor was bad. Replaced it and it still didn't work.  Come to find out that they ran constant power to the motor and ran the ground through the switch to turn off and on.

 

[SuiteSuccess]

Thanks everyone.

[NeverEasy]

What dennisvr said is true of the AC power.  12 VDC comes from Maxi Fuse 5, a 40 amp fuse.  One of those big babies.  That is feed down wire #150 and directly to the AC/Heater blower motor.  Ground is the controller.  The motor speed is determined by the selector switch (or auto climate control if equipped) feeding ground to one of four places.  Wire 161 feeds ground directly to the fan motor for max speed.  Wire 155 is low, 159, and 156 are speeds between low and high.

I had to replace my fan motor some years back.  It was not that difficult.  Care should be taken with routing wires to prevent hitting the fan.  Now, as I remember, when I dropped the cover on the passenger side, the set of resistors that the speed control uses to control speed were right there.  Check voltage on 14-C for 12VDC.  Then check ground on 2-D with the selector to max air.  If those are there and the fan does not blow then the fan is likely bad.

You could jumper 12 VDC and ground to the motor but use large wires.  Fused at 40 amps, the fan will likely draw 20.

Schematics available if you need to see them.  

I might mention, though not relative to this discussion, one other control circuit that uses ground for control is the windshield wipers.  

Chet

[SuiteSuccess]

6 minutes ago, NeverEasy said:

What dennisvr said is true of the AC power.  12 VDC comes from Maxi Fuse 5, a 40 amp fuse.  One of those big babies.  That is feed down wire #150 and directly to the AC/Heater blower motor.  Ground is the controller.  The motor speed is determined by the selector switch (or auto climate control if equipped) feeding ground to one of four places.  Wire 161 feeds ground directly to the fan motor for max speed.  Wire 155 is low, 159, and 156 are speeds between low and high.

I had to replace my fan motor some years back.  It was not that difficult.  Care should be taken with routing wires to prevent hitting the fan.  Now, as I remember, when I dropped the cover on the passenger side, the set of resistors that the speed control uses to control speed were right there.  Check voltage on 14-C for 12VDC.  Then check ground on 2-D with the selector to max air.  If those are there and the fan does not blow then the fan is likely bad.

You could jumper 12 VDC and ground to the motor but use large wires.  Fused at 40 amps, the fan will likely draw 20.

Schematics available if you need to see them.  

I might mention, though not relative to this discussion, one other control circuit that uses ground for control is the windshield wipers.  

Chet

Thanks Chet.

[SuiteSuccess]

Thank heavens was just fuse.  All’s working now.

[Darryl&Rita]

30 minutes ago, SuiteSuccess said:

Thank heavens was just fuse.  All’s working now.

Be aware, that fuse was doing it's life mission, and nonchalantly replacing it will likely result in another death in the future. Time to check over the wiring harness for chafes, scrapes, and rub marks.

[rickeieio]

C'mon Darryl, you haven't met Carl.  He's so lucky, it was probably a defective fuse.  It only lasted 16 years.

[RandyA]

Carl, fuses don't blow for the heck of it.  They are there to protect the wiring from overheating and protect you from a fire caused by something like a short circuit or bad load device.  When a 15 amp fuse blows folks often just put in a larger fuse.  Bad idea!  There is a good possibility your fan motor is drawing more current than it did originally.  This can be caused by brushes wearing out, bearings worn or dry and needing lubrication/replacement or obstruction of the squirrel cage fan movement (to list a few).  That blown fuse could very well be a warning of things to come.

Edited May 18, 2022 by RandyA

[SuiteSuccess]

Thanks Randy and Darryl.  Point taken.  Will investigate further within my skill level (which is limited electrically).

[NeverEasy]

Carl,

What was the fuse number.  The stuff I sent you earlier was Gen I info and would not apply to you (I think).  I looked at the Gen II schematics and there is a lot of difference.  My guess is that the fuse is the Climate Control Fuse, F47, 30 amp.  That feeds the "Blower Control" unit and I can't find a blow-up of it.  

If you let me know the Fuse # and type of fuse I will tell you how to check the DC current draw with your DC clamp-on meter.  

[hatrack]

5 hours ago, NeverEasy said:

Carl,

What was the fuse number.  The stuff I sent you earlier was Gen I info and would not apply to you (I think).  I looked at the Gen II schematics and there is a lot of difference.  My guess is that the fuse is the Climate Control Fuse, F47, 30 amp.  That feeds the "Blower Control" unit and I can't find a blow-up of it.  

If you let me know the Fuse # and type of fuse I will tell you how to check the DC current draw with your DC clamp-on meter.  

Pdf from Volvo customer portal for 2006 Volvo.

Hope this helps,

Ken....

 

https://drive.google.com/file/d/1nwXYZSypcOPRhWJPBQHSjgNnYUatgvHV/view?usp=sharing

[SuiteSuccess]

1 hour ago, hatrack said:

Pdf from Volvo customer portal for 2006 Volvo.

Hope this helps,

Ken....

 

https://drive.google.com/file/d/1nwXYZSypcOPRhWJPBQHSjgNnYUatgvHV/view?usp=sharing

Thanks 

[GeorgiaHybrid]

Carl, to give you some help, the foot bone is connected to the ankle bone, the ankle bone is connected to the leg bone and the leg bone is connected to the hip bone. Forget all about trying anything to do with electrical components.

Like Clint once said, A man has to know his limitations.... 😎

[SuiteSuccess]

9 hours ago, GeorgiaHybrid said:

Carl, to give you some help, the foot bone is connected to the ankle bone, the ankle bone is connected to the leg bone and the leg bone is connected to the hip bone. Forget all about trying anything to do with electrical components.

Like Clint once said, A man has to know his limitations.... 😎

Haha.  I learned that long ago when I looked in the mirror and realized I really had NO resemblance to Brad Pitt. 🤣