AC—oil or no oil?

chast wrote:
Five year old Dometic rooftop air has required service by Dometic each year since installed. Seems to need a new control unit each time. Anyway, thought I’d do a little PM like blowing out the fins, etc. I mentioned that I was going to oil the motor shaft and was told by a self-proclaimed expert that I should not do this? What say you?

I don't know about Dometic but my 12 year old Coleman a/c fan motors have been replaced because of bad bearing fan motors, no where to add oil, the cost of a new motor is only around $150 or so, easy to replace if your handy..

I believe some motors these days use graphite bushings that make it unnecessary. Just an idea but not used to this particular application. This could account for someone telling you to not lubricate, like door locks use graphite or oil but not both.

wolfe10 wrote:

jkwilson wrote:
Sealed bearings are sealed, so oiling accomplishes little. Oil is the wrong lubricant for a bearing in any case, so once the seal fails the motor’s days are numbered unless you remove the seal and grease the bearing regularly.

Let's make sure we are talking about the "care and feeding" of the same type of bearing/bushing fan motors.

I am not aware of any RV roof A/C's with sealed bearings. All I have worked on have sleeved bushings.

Agree, one with sealed bearings would be an upgrade and would be treated entirely differently. A link to one for an RV roof A/C would be appreciated.

Sealed ball/roller bearings would NOT be an upgrade. Note how all shaft bearings used in a home environment are sleeve bearings for a reason. Ball/roller bearings are noisy beyond belief in a home environment. Look at everything that has a shaft in your home. It is supported with sleeve bearings. Ball/roller bearings make so much noise and vibration that they can not be used in a printing press, as the vibrations shows up in the print.

Richard

jkwilson wrote:
Sealed bearings are sealed, so oiling accomplishes little. Oil is the wrong lubricant for a bearing in any case, so once the seal fails the motor’s days are numbered unless you remove the seal and grease the bearing regularly.

Let's make sure we are talking about the "care and feeding" of the same type of bearing/bushing fan motors.

I am not aware of any RV roof A/C's with sealed bearings. All I have worked on have sleeved bushings.

Agree, one with sealed bearings would be an upgrade and would be treated entirely differently. A link to one for an RV roof A/C would be appreciated.

Sealed bearings are sealed, so oiling accomplishes little. Oil is the wrong lubricant for a bearing in any case, so once the seal fails the motor’s days are numbered unless you remove the seal and grease the bearing regularly.

Many of the motors today have a fiber washer (slinger ring) on the shaft inside the cover that would prevent any oil dripped on the shaft from actually getting in to the wicking material that keeps the bearing lubed. You almost need to disassemble the motor to get at the wicking and put the oil right on it where it will do the most good.

In the old days, they used felt pads for wicking. More recently it looks more like shredded tissue paper. Like Brett said, non-detergent oil - 20w preferred.

The wicking is meant to last about 5-6 years. All these comments are for sleeve bearings. There are very few ball bearing motors out there in residential air conditioning systems.

It certainly wont hurt anything. Wipe off any excess afterward though.

Can't imagine NOT oiling with a light viscosity non-detergent oil like sewing machine oil when you are up there.

Older units even have plastic plugs that you can remove to allow oil to go into the bushing areas. On newer units without those oil channels, putting a few drops on the shafts next to the bushings will allow some to wick in.

Would appreciate the reasoning behind not lubing the fan motor bushings.

Oil it, I do mine. Won't hurt anything.