Bad Blower Motor
Earlier this week a 2016 Ford Escape came in with a complaint of the blower motor only working on high. After confirming customer complaint, a visual inspection and then some research I found the vehicle had a blower motor resistor and not a blower motor module. So I printed off a wiring diagram and went to testing the blower motor resistor which to my surprise tested out good. I decided to pull out the lab scope and hook up a amp clamp to the fuse for the blower motor. The waveform I collected showed the blower motor was the problem. This made me wonder how many techs would have just thrown a resistor at it and a few techs I talked to said that's probably what they would have done. I know this is a simple case study but I have only been doing diagnostic work for a couple years and this made me want to give thanks to all those who help techs like me learn to do diagnostics. Sorry I don't have a after repair waveform since customer declined the work.
Did you check for TSB's? I think I recall that Ford put on out on this.
Good memory Peter! SSM 47797 regarding a bunch of Fords (but not the Escape) having bad connections at the blower control switch connection could certainly cause the Hi Blower Only symptom.
Tommy, Can you explain more on how the amp capture proves the blower motor is the reason for high only? Is the manual HVAC? What fuse was this taken from?
Hi Glen, You spark a really good question. Wondering if the poor connections at the control head that Peter referred to is the root cause of the no blower (on any speed but high) and the motor is just an old motor that runs but puts out a bunch of crappy hash. As a working analogy I've current ramped a few functional fuel pumps with similar nasty patterns. A nasty pattern pump might last for X…
Hi Tommy, Thank your very much for your case study. Peter Coll's comment got my curiosity regarding the TSB - so I looked for one. There is a Ford SSM (Special Service Message) 47797 for a bunch of Fords (but not the Escape) describe the assumed "crispy critter" terminal connections at the blower control switch. I would guess if a bunch of other Ford models had connection issues at the HVAC…
At the time of working on the vehicle i didn't find any tsb about the control switch. The vehicle has manual ac and I had my amp clamp hooked up at the 40amp blower motor fuse. It is fuse #10 in the under hood fuse box. David if you would like to use this waveform capture that would be fine.
I recently came across the same where other technicians and dealerships kept throwing parts and wiring overlays at it since the blower motor was replaced once before. Even more confusing when the client describes his problem as 'AC is not blowing cold' when he actually means 'AC does not blow air at all sometimes'. Some digging through my warranty paperwork and found the attached screenshots of…
HI Vincent - thanks for posting your scope patterns. Super easy to see the difference! Motors are motors whether they pump fuel or move air. May I use your images (with credit to you and DN) in an upcoming MACS (Mobile A/C Society) service report?
David, sorry for the late response! Feel free to use them with or without credits!