Hey guys,

I have a 1993 E350 Econoline-based RV. The blower motor intermittently makes a horrible whirring/buzzing sound, usually if on position 3 or 4 (high). Doesn't stop until I turn the HVAC to Off. The blower motor vibrates quite a bit while making this noise (verified with my hand). The problem occurs even if the engine isn't running. This started a few years ago, and has simply gotten worse.

Since it runs OK at the lower speeds (until the problems start with the higher speeds), I think that means I can rule out something simple like debris?

Also, when the engine is under load (climbing hills, etc.), the blower fan cuts out. Could that be a resistor problem, or something else?

I poked around with search, nothing quite matches my symptoms.

Thanks.

Mike

 

This sounds like the blower motor itself is failing. Electrical problems as in with circuits etc don't induce vibrations or operating noises.

Why a blower motor would cut out during heavy demand on the engine escapes me. Is it possible the air flow is re-directed rather than a loss or great reduction in actual air flow?

 

I loathe blind part-swapping, but I'm leaning towards replacing both the blower motor and the resistor while I'm at it...


Mike

 

Remove the blower motor so you can direct-wire it to a 12 VDC source---if its the cause of your vibrations etc it should be obvious while its running.

Since you'd already be working in that area the resistor network could be visually inspected too. Just for kicks double check the wiring harness connector as they've been known to cause issues too.

 

Thanks for the help guys, here's a quick update...

Took out the resistor, that looked OK, except for some debris on it. Replaced it anyway.

Removed blower motor and pulled the wheel off to clean it. It also had some debris.

The debris was fibrous, like the fibers in the hood panel which has been chewed by vermin over the years for nest-building purposes. There was no sign of critters or nests inside the housing, I think the fibers just got pulled in over the years.

The plastic wheel has some slightly damaged fins, so I'll replace it to rule that out as a cause.

I did hook up the old motor (without the wheel) and tested it after replacing the resistor. It wouldn't turn at all on low, but did spin in the other settings. The shaft got pretty hot while testing it, not sure if it needs to be pulling air with the wheel to cool itself?

Anyway, plugged in the new motor, works great on low (I didn't bother with the other speeds, mainly out of concern about it overheating).

So, I'm chalking this up to a bad motor and wheel, and an iffy resistor...

I'll try to get some pics up later.

Mike

 

Ugh... Apparently, the motor design changed (the tube entry location doesn't match), and the tube design did as well. The new motor also didn't come with a new seal. The old seal was stuck to the motor (not the housing), so I can't re-use that.

So, now I need dealer parts (tube and seal) as well as a wheel, which comes up on the parts diagram, but the number isn't listed as being available from Ford. Advanced has one.

3 parts away from being done. Oh, and the new connector isn't going to be able to work with the wire retainer, so I'm going to have to MacGuyver something for that too. Good times...

Mike

 

OK, have parts...


The wheel (aftermarket) is metal (original was plastic).


The gasket doesn't have a sticky side. That ought to make installation a blast...


The tube looks fine.


Should be able to wrap this up over the weekend. Also working on a brake job on this unit...


Mike

 

Aside from dropping a screw into the engine bay, this went together easily and works great. I found the screw, which would have found its way into my rear tire for sure.

Used some double sided tape to hold the gasket in place while installing the blower.

Should have done this years ago...

Mike

 

Well, the new motor works great. No decoupling sounds at all.

However, the system does still reduce flow with various engine RPMs (usually under heavy load). Any ideas?

Mike

 

What does this mean exactly? How is flow reduced, what's actually happening when this is experienced?

 

OK, when running AC or Vent, flow stops. This is usually when climbing a hill or otherwise stressing the engine and tranny.

I'm wondering if it's vacuum related, but there are no issues with operation of the engine or tranny, and no codes.

Mike

 

Your changing air flow is definitely vacuum-related, most likely the reservoir for HVAC flow control has developed a leak or otherwise not holding vacuum in reserve when/if the engine is under load and producing less vacuum.

This is typically fixed by adding another vacuum reservoir and plumbing around the existing part because its too much work trying to find and replace it.

There are several threads about this issue, try this link: https://www.ford-trucks.com/forums/1...efrosters.html Read the entire thread as it offers several ways to effect this sort of repair.

HTH

 

Wow, that sounds exactly like the problem with this RV. Thanks!

Mike

 

I won't be able to play with this repair for a few weeks due to other commitments, but I'm sure I'll need to do the bypass.

I think that it would be great to pull those threads into a common thread, and make that a sticky at the top of the HVAC and van sections.

Mike