Amps in blower

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eitanuch

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Hello
I've just took up the blower of my car for repairing. It's a VW polo 2008.
I want to make sure it works correctly so I took some measurements and I found out it takesup to 16 Amps at 12 Volts. Does it make sense? At first I thought it might has a problem because 16 Amps sounds too much.
 
Not really... It has a 30amp fuse.. But 16 amps will put a toll on the resistor pack.. The blower on VW cars have a resistor pack in the air flow near the heater blower.. Once the blower gets tired these resistors blow.. Then you only get high speed and no lower speeds.. There is also a flywheel diode that gets damaged as well..
 
Are these parts inside the blower? I took it off completely (powered the motor by an external PS) and couldn't see any of those.
Can I repair it anyhow, besides cleaning?
 
Looks like this


Completely separate to the blower... The diode is at the back... It will be in the air flow somewhere..
 
I always put diodes in series... Manufactures never allow for motor wear.. They always assume you'll replace it.. My last polo worked for years after I upgraded the diode.. Get two 10A diodes and parallel them up...
 
Did you test it off the auto? If so this is where the current will be at maximum.
If a radial or axial fan, the current will Decrease as the air flow decreases or is restricted in any way, vent louvers etc.
Max.
 
Well I think I'll test that tommorrow again, connected to the auto's circuit.
I've tested it off the auto as I mentioned...
 
hyedenny said:
I hope you're not talking about that thermal fuse -- that's not a diode!
Click to expand...
LOL!! That must be why it worked so well!! I've always thought it was a diode.... If this is correct, a thermal fuse will blow again... so a diode will work as I said... Otherwise, its a new fan unit!!
 
I have seen another type of protection used on heater blower resistor packs, where it seems a shunt is under tension and then soldered.
Excess current draw from the motor heats the shunt enough to melt the solder and the shunt springs away, opening the circuit.
Can't remember which manufacturer used it though.
 
16 A isn't too much, but at 10 years old take a look at the brushes and inspect for brush wear and uneven wear on the commutator. 16*12=192 Watts or about 1/4 HP.

Even though brushes may not be available, I did visit a vacuum cleaner store to pick out suitable brushes for the motor in one of my vehicles. It had an issue where the blower would fall through it's friction mount. When I found out, the OEM fix wasn't available anymore. I was able to file the brush to fit and shrink the brush holder with a soldered brass shim.

The speed resistors are usually in the plenum and cooled by the blower. When they die, you loose all speeds but high.
 
I'll reply to eitanuch and mikster on this issue.
I drive a 1998 Dodge Ram half-ton van with a blower resistor assembly having a thermal fuse. I get only full blast fan speed when that fuse blows, off-the-shelf thermal fuses are underrated for the fan's 17A current draw. The 25A fuse in my fan circuit caused the harness wires to melt together resulting in no fan speeds available. I'm designing a switching circuit using an R-2R ladder and MOSFET, with 311 and three CMOS IC's.
 
I've (recently) seen larger fans in cars take 20-25 Amps with a much higher initial surge. Most newer cars are now using PWM to control the fan speeds on both the radiator fans and heater fans.
 
picbits said:
I've (recently) seen larger fans in cars take 20-25 Amps with a much higher initial surge. Most newer cars are now using PWM to control the fan speeds on both the radiator fans and heater fans.
Click to expand...

Citroen have been using PWM to control their heater fans for a VERY, VERY time, certainly back last century. I only know because a friend of mine is a Citroen fan, and asked me to repair one out of an old Citroen he had.
 
Nigel Goodwin said:
Citroen have been using PWM to control their heater fans for a VERY, VERY time, certainly back last century. I only know because a friend of mine is a Citroen fan, and asked me to repair one out of an old Citroen he had.
Click to expand...
Didn't some of them have a TO3 transistor as their output stage ? I vaguely remember being asked to repair one once.
 
picbits said:
Didn't some of them have a TO3 transistor as their output stage ? I vaguely remember being asked to repair one once.
Click to expand...

I can't remember, it was a good while ago now - but I seem to recall it was actually a nice simple repair (and didn't require access to the car).
 
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