99 EB Explorer a/c volume surges while driving

[iajet]

It is most noticeable when I back the setting off of max just a bit. Thoughts?

Thanks

 

[J_C]

You mean flow rate like the blower motor is changing speed, or could there be a vac problem and some is getting diverted to the defroster duct?

 

[iajet]

Yes, like someone is manipulating the setting and turning it up then down every few minutes.

 

[J_C]

I'd suspect the motor brushes or bushings/bearings are going out. These are not normally user-servicable, IIRC it's a stamped or welded together design. You might be able to pry it open or drill out rivets and substitute screws to reassemble (if you can find the typical LONG, thin screws used for that) and lube the bushings or check the brushes, but most often it's time to replace it.

If it is time to replace it you can try to get the plastic squirrel cage fan blade assembly off first. Sometimes they come off and sometimes they break, which will tell you if you need to buy the motor with a new fan blade assembly or can reuse the old one.

 

[iajet]

Thanks

 

[J_C]

In theory it is also possible that instead of the blower motor, that your console switch (or whole head unit if it's EATC, auto climate control) is failing. However that would tend to be more reproducable sitting in the driveway and measuring for a voltage change with a multimeter, on the fan power connector.