Bench checking 6 volt heater fan motors

[A. Amman #15293]

Would it cause any harm to check a 6 volt motor for functionality using a 12 volt lawn tractor battery and connecting it very, very briefly? 

Thanks,

A. Amman#15293

[Dave Shepherd]

Don't have access to a shop battery charger, they have a 6v setting.

[Walter Youshock]

That's what I was going to suggest.  I use my charger to bench test just about everything but radios.  Never had anything 6 volt, but a battery charger is relatively cheap and can pay for itself in a short period of time.

[A. Amman #15293]

Hey guys, thanks for the information.  I took a look at my motorcycle battery charger and it has a 6 volt, 6 Amp feature.  I hooked it up and got no sparking and no rotation.  I then hooked my volt meter to the charger leads and got no reading even with it switched on.  It seems like the charger "knows" it isn't linked to a real battery?  Is that possible?  The motors worked when tested several years ago, but I want to make certain as I have the front seat frame out of the vehicle and upholstery going in so I don't want to have any access problems with the heaters once seat is back in place.

A. Amman #15293

[Martin Michaels]

I keep a 6 v dry cell batterie with alligator clips on my bench for checking all 6 v problems. Marty

[J. Gomez]

Amman,

If you have no source for a 6V supply, to safeguard the fan connect a 12V bulb in series with the fan and the 12v supply. Depending on the bulb filament resistance the fan may run slow or not, an 8-10 ohm 25 watt resistor would also do the trick. This should allow roughly a 6v drop across the bulb or resistor.

Good luck

[A. Amman #15293]

Ok, so here is where I'm at on this deal.  I tested the motor leads to make sure that I have continuity through the windings and that checks out.  As long as the motor is in the heater housing with the ground lead attached to the metal housing, should it not run when I connect a hot wire to the positive side and my negative lead to the ground lead attached to the housing?  I did take the motor, put it on the bench, hooked up my leads, got a boat load of sparks but not any rotary motion.  I also grounded the motor to my tool box for good measure.  I make no claims to being an electrician so what's up with this thing?

Marty, I did try the dry cell 6 volt approach which I use to check wires and bulbs with but it did not spin this motor.  Not enough juice?

A. Amman #15293

[bcroe]

Modern DC motors have permanent magnet stators, and can only be
operated on DC.  But your 6 volt motor has a wound stator.  The simple
way to operate it, is connect direct to 6V AC, a transformer output.  It
will need a rather substantial current rating to properly operate the motor. 

In truth, I have operated vacuum tube/vibrator radios from AC.  Any
semiconductor parts or perhaps a fancy tuning control might rule this out. 

Smart battery chargers may have sensing circuits, that limit output until
a battery is detected to the terminals.  Use a battery with the charger. 

The 50s DC battery eliminators designed for radios (Electro D612T, etc),
won't supply enough current to operate the motor full speed.  But turning
the voltage up gradually should at least spin the motor, going a little higher
after starting surge before passing the 10A limit. 

To answer the original question, a VERY BRIEF connection of 12VDC to the
motor should cause no problems.  Be sure the fan is on the shaft so it can't
over rev; best to have it bolted down for the surge; expect QUITE an arc
when the circuit is broken a half second later. 
Bruce Roe  CLC # 14630

[bcroe]

I did take the motor, put it on the bench, hooked up my
leads, got a boat load of sparks but not any rotary motion.     A. Amman #15293     

With no power, can you spin the shaft freely?  If not the sleeve bearings may be frozen on the
shaft.  If the motor can be taken apart without damage, and the bearings polished up, it ought
to be good for a long time (keep it oiled).  If the bearings are so worn the armature has been
scraping, replace bearings (or motor).  Bruce Roe

[A. Amman #15293]

Thanks for the information, Bruce.  The motor shaft spins freely with no binding.  I will see what I can figure out and report back later.

A. Amman

[bcroe]

I will add, I was assuming it is a series motor, so any current must pass through
the brushes & armature.  It could have a shunt field winding allowing some
current to flow even if there are bad brushes or other blockage of armature
current.  A series-shunt combination works; I doubt its totally shunt.  Look
inside for ability to pass current through all elements.  Bruce Roe

[A. Amman #15293]

I could get nothing to happen with the testing I was doing so took the part down to our local starter, generator, alternator shop for a look over.  They could not get it to run either but the man who might be able to won't be back until Monday, so will see what he can figure out.

A.Amman #15293

[william_b_noble]

you can put it in series with a headlight bulb - a 15 to 30 amp bulb will protect the motor and also let you see how much current it is drawing from your 12V battery.  note you may have stuck brushes, a sharp rap with the back of a screwdriver or a rubber mallet may fix that

[Martin Michaels]

If you are getting a boat load of sparks and no movement of fans, I suspect you have a short in the armature.When the man gets back from the starter place he will be able to tell you. Are both motors having the same problem? Marty.

[A. Amman #15293]

Thanks J. Gomez and Bill N. for the light bulb in series tips.  Marty I have not tried the other motor yet but will tomorrow.

In the meanwhile I spent several hours googling various configurations of ways to search for blower motors, heater motors, 6 volt, etc. ad infinitum.  I found two sellers who deal in NOS and NORS stuff, one located in Texas and one in Michigan for all makes of vehicles.  There used to be a place in Milwaukee, Wisconsin by the name of B. S. Wisniewski or"Wizzy's" and they had virtually everything you might need for most Americam made cars.  They have been gone for years unfortunately. 

A.Amman #15293

[Martin Michaels]

If you need a replacement motor try Eddie Jones I dpnt have his number handy I will post it later. He is great I bought a lot from him& he is reasonable. Marty

[A. Amman #15293]

So, the Technician was able to repair the heater blower motor and what he found was a collapsed spring which he replaced as well as undercutting the commutator.  All for the bargain price of $25.00!  I'm very pleased that I get to keep my original motor.  I'll check the other one now and see if it's still operational or if it needs to go in for a "tuneup".

A. Amman #15293