Hoover vacuum brush roller motor only runs for a few seconds

[FM]

Help, please.  Bought a new brush motor for it, and it does the same thing, so figure it has to be a circuit board problem.  There's a lot of people on the internet with this problem but no fix. 

The main motor works fine.  When you press the brush roller button on the handle, the brush roller motor turns on, then shuts off after about six seconds.  It does it without the belt attached, so it's not a hair clog or similar on the brush roller bar.

Hoover 72400RM Air Steerable vacuum.  That may be a model number for refurbished versions of this vacuum.  Other models that look the same at least on the outside are Uh70400, Uh70402, etc. 

 Anyone heard of this problem before or has some ideas?  As I type this, I probably should have checked the resistor values already but have not.  And then I'm out of ideas.

One wire plug on the board goes to the lever/switch that disables the brush roller when the vacuum is upright.  That works properly.  The other plug goes to the brush roller motor.

[timenutgoblin]

If you're able to, check and replace the large red capacitor. It looks like an AC voltage-dropping capacitor. Also consider checking for any dry joints. Do you notice any components getting warm or hot? Please do not touch the circuit when powered up.

[james_s]

Is it in good shape mechanically? I have had this problem with my Dyson cordless vacuum a few times. If it detects binding it will stop the brush motor, so when it gets enough hair and lint and stuff wrapped around the brush and bearing it starts shutting off.

[Gregg]

Also check the surface mounted ceramic caps for cracks; Dave did a video about this

[FM]

Thanks.  It'd make more sense if the brush roller didn't turn on at all instead of turning on but then off 4 seconds later.   

No components hot.  I let the vacuum run for 5 minutes and pressed the brush roller button to turn it on (for 4 or so seconds) numerous times and checked it.

The roller can't be binding the motor because the belt is removed from the roller.  The motor is sitting in open air.

I don't have more than a handful of resistors around, so if I change the red cap it won't be soon. The numbers on it by the way are MPP 155j400V   and then www sdkj and then 1 or more letters that are blocked by the little red cap in front of the big one.

I don't see any dry joints.  Will try again on that and the cap for cracks tomorrow when there's natural sunlight maybe that will give me sight beyond current sight.



 

[cruff]

Some times you can't see a bad solder joint. I had an oven that would loose power on the control board and reset when cooling off after use, but would always come up to temperature again when I next needed it. Then it started resetting during a cooking session, so I took out the control board and examined the joints with a magnifying glass, but I didn't see anything obvious, and no components had obviously failed. I reheated the solder joints in the power supply section, and went so far as to redo the joints at the connectors. Since then the oven has been working properly.

[amyk]

Looks like a standard brushed motor, easy enough to hardwire a switch to turn the motor on as long as you want...

If you really want to fix it to stock, then you can try to trace out the schematic of the circuit board.

[DavidAlfa]

There's no other "smart" board controlling the power stage?

[FM]

Looks like a standard brushed motor, easy enough to hardwire a switch to turn the motor on as long as you want...

That's a question too. 
There's apparently many different model numbers for the Hoover "Air Steerable" vacuum.
The model number on mine didn't match up to anything, (maybe because it's a factory refurb), so I matched up the writing on its motor.

Bought a new motor for it from Amazon because the pictures looked like the original motor.
The original motor and those pictures say 120v/60hz.
But the motor that arrived has a label that says "DC" on it. 
As far as I know, if it's a DC motor, it needs the circuit board to not burn up.?  Or, the replacement motor is simply labeled wrong.

Pictures below of:
the original (rusty) motor.
Matching pic from the Amazon listing: https://www.amazon.com/Hoover-Nozzle-Uh70400-Uh70401-Uh70402/dp/B00Y348LT6/
New motor that arrived from that listing.
Both motors do the same shut off after 4 seconds thing.

[amyk]

Does it have a wound field (universal motor) or is it a permanent magnet type? From the pictures it looks like the latter, which would definitely be DC only, so there should be a rectifier on the board if so.

From a brief search at vacuum roller brush motors it seems they're all permanent magnet type, like the common "540" or "550" size, but wound for mains voltage.

[james_s]

Those are both permanent magnet DC motors.

[FM]

Thanks, everyone.  Having holiday guests stay over for days brings its share of chaos, but one of the guests used to work professionally with circuit boards, so I was waiting for them to look at the solder joints.  We re-soldered three "maybe there's a small chance they're bad but most likely they're fine" joints.  No change.   

About the only things left to try are reheating all the joints and changing the red cap.  I won't leave you hanging if there's a change.               

[CapLeaker]

I've had a couple of power supplies that behaved like that. In one case the trouble was the startup resistor to a PWM. Each time I applied power, the resistor would go from its normal value to practically open in 5 seconds, cutting off power to the PWM, then the PSU died until the resistor cooled off (unplug, wait, repeat). The other case was a dirty through hole from an inductor on one of the output rails. Again it would work good for up to 30 seconds, then quit, run time depending on temperature. The dirty through hole on the inductor made the voltage on the output drop and spike a little (unstable). It did it as long until protection kicked in. That surfaced after 10 years operation. The only way to fix that was to take the inductor out, clean the hole then re solder the component. Just a re solder didn't help.

Good luck on your venture!

[NOON Design]

I recently repaired a robot vacuum with a dead brush motor. It was physically restricted by hair etc that that had put too much load on the motor and back through the system. I ended up replacing the motor, the driver FET and a current sense resistor that was supposed to detect the clogging and shut it down. Your system may have a similar fault in the detection circuitry making it think there's something restricting the motor. If a resistor has overheated and drifted in value it will be giving incorrect voltages to the controller.

[FM]

Update. 
Changed both red caps.  No change.

That's probably going to be the end of messing with it.  Thanks, everyone. 

On the bright side, a couple hours after that didn't work, I changed some puffed up caps in my 10-year-old 1080p TV, and now that works again. Of course, I had already picked up a bigger and better 4k HDR TV less than half its age for $50 to replace it, and now don't have any use for the ancient 1080 TV that is barely worth anything. haha

But, with its puffed up caps, the fix seemed a high probability, so of course had to find out.

[jchw4]

I recently repaired another Hoover. Mine was very different, but the rusted motor suggests that the issue could be the similar.

In my case the front bearing rusted through and stuck on a shaft.
The bearing sits in a plastic front cover. This way it's not attached to the cover, it just sits there.

After it got stuck the shaft started rotating with the bearing sliding against the plastic housing.
In a second or two plastics melted a little bit, bearing got stuck and blew the fuse.

In my case it was a primary motor, so it was connected directly to the mains, had a regular fuse and no other electronics.

This way after it blew up the second fuse I knew that it was the motor itself that somehow killed the fuses. So I did not have another option but to disassemble it.

I feel that it could be your issue too. Like motor consumes too much current and the power supply cuts it off.

With functional bearing rotor shoud rotate freely. I.e. if you spin it by hand it should continue rotating for a few seconds (>5) after you stop.

In my case I could rotate it by hand and it did not feel stuck. But it stopped freewheeling pretty soon. So I found the issue only after the disassembly.

I did manage to replace the bearing (the front bearing was some very common "scateboard / rollerboard" type that are sold in packs on Amazon).

But disassembling (and assembling it back) was pretty difficult. I used a nearby makerspace with full size mechanical workshop for that. Press-fit bearings are relatively difficult to replace.

Upd: I missed the fact that you replaced the motor. But if they used a polyfuse it could degrade and start tripping at a lower current.