SmokeyBare
Well-known member
There are two fans on an A/C unit... one blows the cold air through the Duct work inside the RV.... the second blows air across the Condenser coil on the roof of the RV.
To decide which fan is causing the problem... turn the "FAN" switch from "AUTO" to the "ON" position... this will turn on the blower inside... but not run the A/C. Now check to see if it's causing the vibration.
I'm betting it wasn't that fan... Soooo next switch the "Heat-Cool" switch to "Cool"... If the vibration shows up... you now know where to look. ON the Roof of the RV... under the A/C Cover.
Not sure it's a place you want to go... but if you do... be sure to have the unit "OFF"... and look for any damage or bent fan blades... look for "Mud Dobber" nest built on one of the fan blades... spin with your fingers and see if they are all running in line... no wobble....
Good Luck with your investigation...
To decide which fan is causing the problem... turn the "FAN" switch from "AUTO" to the "ON" position... this will turn on the blower inside... but not run the A/C. Now check to see if it's causing the vibration.
I'm betting it wasn't that fan... Soooo next switch the "Heat-Cool" switch to "Cool"... If the vibration shows up... you now know where to look. ON the Roof of the RV... under the A/C Cover.
Not sure it's a place you want to go... but if you do... be sure to have the unit "OFF"... and look for any damage or bent fan blades... look for "Mud Dobber" nest built on one of the fan blades... spin with your fingers and see if they are all running in line... no wobble....
Good Luck with your investigation...
abinns
Member
Thanks for the quick responses. I've done your recommendations. It appears to be the fan. It is quieter on High, but still vibrates. Low fan rattles the windows. I've checked behind filter and looked for loose objects, but found nothing . Haven't been on the roof to look under cowling. It has to cool down outside first. It's still cooling really well.
Rickhansen
Well-known member
Don't wait too long, any significant vibration is bound to be hard on the fan motor bearings.
Abinns
Check the squirrel cage on the fan for dirt dobbers nest. The exact same thing happened to a friend of mine last fall when we arrived at a GS ralley. His unit had been parked in storage for a couple of months and he did not check out the AC before he left. When he fired up the AC it sounded as if the roof was going fly off. We climbed on top and pulled the shroud off and the fan there seemed good. We then took off the cover inside the unit and the nest was in the squirrel cage of the circulating fan. Be carefull when you start poking around. The same thing happened to me many years ago in a TT and the problem was a wasp nest!!!!! Ouch! they tend to attack when disturbed! Good luck.
Check the squirrel cage on the fan for dirt dobbers nest. The exact same thing happened to a friend of mine last fall when we arrived at a GS ralley. His unit had been parked in storage for a couple of months and he did not check out the AC before he left. When he fired up the AC it sounded as if the roof was going fly off. We climbed on top and pulled the shroud off and the fan there seemed good. We then took off the cover inside the unit and the nest was in the squirrel cage of the circulating fan. Be carefull when you start poking around. The same thing happened to me many years ago in a TT and the problem was a wasp nest!!!!! Ouch! they tend to attack when disturbed! Good luck.
abinns
Member
Update: You were right....dirt dobbers nest on the squirrel cage. Fortunately we had the bedroom AC for last night so we didn't have to keep running it. Should have suspected dirt dobbers nest....we have them everywhere in our shop....even get up into our chairs inside their covers....up jacket sleeves....But, many thanks for the quick information and heads up. Easy fix in the cool of the morning.....
Ronnie and Anita Binns
Quitman, AR
2008 Big Horn 3600 RL
2008 Chevy 3500 Dually
Ronnie and Anita Binns
Quitman, AR
2008 Big Horn 3600 RL
2008 Chevy 3500 Dually
