Jump to content

Dash Air Condenser Fan Not Running


trailmug
Go to solution Solved by Frank McElroy,

Recommended Posts

2008 Signature, I've done extensive work on the dash a/c system over the years, but have yet to run into this.. no power to the condenser electric fan when the compressor is engaged. Goes off on high head when parked (obviously, thanks binary switch). This one doesn't have a switch-controlled fan, so I presume it gets its power from either a discrete power relay or the chassis multiplex unit or fuse box in the front pass-through bay. I always assumed it ran off of the clutch relay, but apparently not. Having trouble finding the condenser fan circuit on the wiring diagrams. The cable does appear to go to the front cargo bay, but I thought I'd reach out and see if anybody had knowledge of how it gets power.

Thanks,
Rob

Link to comment
Share on other sites

I know the Signature is a far different beast than my Endeavor a 2008, but I imagine the AC systems may be close. Do you have a panel below the driver in the outside compartment?

If so, there are some small relays in there and a fuse as well. I have diagrams and notes in case you have something similar. 

Link to comment
Share on other sites

  • 3 weeks later...
  • Solution
On 10/31/2023 at 2:59 PM, trailmug said:

2008 Signature, I've done extensive work on the dash a/c system over the years, but have yet to run into this.. no power to the condenser electric fan when the compressor is engaged. Goes off on high head when parked (obviously, thanks binary switch). This one doesn't have a switch-controlled fan, so I presume it gets its power from either a discrete power relay or the chassis multiplex unit or fuse box in the front pass-through bay. I always assumed it ran off of the clutch relay, but apparently not. Having trouble finding the condenser fan circuit on the wiring diagrams. The cable does appear to go to the front cargo bay, but I thought I'd reach out and see if anybody had knowledge of how it gets power.

Thanks,
Rob

This fan is powered from the rear Kongsberg CCM located in the ceiling of the first bay behind the steer axle.  The panel between the frame rails will need to be removed to gain access.  Open the black CCM cover and the 30 amp fuse F2 and relay K3 are for the condenser fan motor.  Most times this motor goes bad and pops the fuse.

  • Thanks 1
Link to comment
Share on other sites

In case you don't have them, here is a link to a set of wiring diagrams for your coach.  To get the option to download all pages in one file click on the title (not download) in the link below.

 

1 hour ago, trailmug said:

Thanks, exactly what I needed. I was worried it would be one of the solid state outputs on the Kongsberg like the big boy boost switch which blew, I assume due to inadequate diode protection. I can live without the batt boost, but not the condenser fan. 😁

The battery boost switch not working is likely due to a failure of a component on PCB #6 in the rear run bay.  I've seen this a number of times on your model year coach.

This board has the remote battery boost and salesman switches on it.  The led lights on the board will help identify the problem.

Link to comment
Share on other sites

  • 8 months later...
Posted (edited)

Thanks, the fuse was easy to identify after taking the access panel off the front cargo bay (turn A/C on, and probe for the fuse with 12 volts across it). Fan was locked solid and fuse was blown, as predicted. The Flex-a-lite 239 was a good fit in this application. Noisier than stock, but seems to move more air. Can't hear it over the road noise so I don't mind. The mounting ears transferred right over and I didn't have to modify anything. I also suspect that the original fan was not wired correctly with reverse polarity as is necessary with a pusher fan. I matched the original polarity after confirming with a bench PSU and the fan ran backward.

Curiously, the Kongsberg runs the Big Boy coil directly off of one of its solid state outputs instead of utilizing a relay. The kickback from the big boy seems to have roasted the solid state output. At one point I wired up a relay to close the switch while the generator start button was held down, but that didn't provide me enough help starting the generator with depleted domestic batteries. The ultimate solution was to put a starting battery under the nose cone on the side of the generator:-)

Edited by trailmug
  • Like 1
Link to comment
Share on other sites

8 hours ago, trailmug said:

Thanks, the fuse was easy to identify after taking the access panel off the front cargo bay (turn A/C on, and probe for the fuse with 12 volts across it). Fan was locked solid and fuse was blown, as predicted. The Flex-a-lite 239 was a good fit in this application. Noisier than stock, but seems to move more air. Can't hear it over the road noise so I don't mind. The mounting ears transferred right over and I didn't have to modify anything. I also suspect that the original fan was not wired correctly with reverse polarity as is necessary with a pusher fan. I matched the original polarity after confirming with a bench PSU and the fan ran backward.

Curiously, the Kongsberg runs the Big Boy coil directly off of one of its solid state outputs instead of utilizing a relay. The kickback from the big boy seems to have roasted the solid state output. At one point I wired up a relay to close the switch while the generator start button was held down, but that didn't provide me enough help starting the generator with depleted domestic batteries. The ultimate solution was to put a starting battery under the nose cone on the side of the generator:-)

On a Kongsberg coach, the battery boost signal from the rear CCM mosfet is sent as a separate input to trigger a circuit on PCB#6 in the RRB to power the big boy coil - there is no coil kickback to the Kongsberg CCM. That separate circuit board is what controls and powers the big boy relay.  If the CCM mosfet has failed, it would be the first time anyone posted about it.  Please confirm that the battery boost switch module is working by pressing and holding the Dimmer + switch to see if the battery boost label lights up.  Also, if the wire from the rear CCM to pcb#6 is broken, you won't have battery boost.

Link to comment
Share on other sites

Posted (edited)

I was able to send power from one of the large screw terminal outputs on the CCM to PCB6 using a relay (triggered by splicing into Gen start output) and the existing wire which was originally connected to the CCM 👍

If memory serves, it did not have the usual square wave sound of the big boy driver, so I assumed it was just a direct feed. The coach actually came with a second battery boost switch which I installed without success.

Were you on the engineering team? That is a wealth of information 🙂

PXL_20240729_025111381.jpg

Edited by trailmug
Link to comment
Share on other sites

7 minutes ago, trailmug said:

I was able to send power from one of the large screw terminal outputs on the CCM to PCB6 using a relay (triggered by splicing into Gen start output) and the existing wire which was originally connected to the CCM 👍

If memory serves, it did not have the usual square wave sound of the big boy driver, so I assumed it was just a direct feed. The coach actually came with a second battery boost switch which I installed without success.

Were you on the engineering team? That is a wealth of information 🙂

PXL_20240729_025111381.jpg

Actually, the battery boost input signal to PCB#6 is ground - not 12 volts.

Nope, I was not on the Monaco engineering team.  Just a 17 year owner of my 2008 Dynasty doing all my own service and an electronics background as an amateur radio operator who built my own station back in the 60's and a PhD in electro chemistry building and machine code programming a micro computer in the 70's. 

I enjoy an electronics challenge.  The Kongsberg chassis multiplex system sure was a challenge to understand and repair.

  • Like 1
Link to comment
Share on other sites

Posted (edited)

Next time I have the access panel off again, I'll probe around. Entirely possible I forgot grounding that wire vs powering. I removed the relay since the big boy didn't help much to start the genset.

I assume the CCM is getting the CAN signal since the other buttons work. I guess for a bonus, I could scope it while pushing the solenoid trigger button on PCB6 😁

Edited by trailmug
Link to comment
Share on other sites

31 minutes ago, trailmug said:

Next time I have the access panel off again, I'll probe around. Entirely possible I forgot grounding that wire vs powering. I removed the relay since the big boy didn't help much to start the genset.

I assume the CCM is getting the CAN signal since the other buttons work. I guess for a bonus, I could scope it while pushing the solenoid trigger button on PCB6 😁

PCB #6 supplies a constant 12 volts to one side of the big boy coil and pulses the other side to ground.  The square wave basically is providing 8 volts across the coil for continuous duty without burning up the coil. 

When you press battery boost, the rear CCM mosfet is sending a constant ground signal to PCS#6 which then shuts off the pulsed ground signal converting it to a constant ground 

The PCB #6 does have push buttons on it to remotely operate the battery boost and battery disconnect (salesman switch) from the RRB.  If big boy is engaged with the pulsed ground signal and the familiar hum, when you press the remote battery boost, the hum will go away because the pulsed ground is now a constant ground.

Yes, since the dash switch module lights up, it's very likely to generate the correct digital battery boost code.

  • Thanks 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...