[T3] Breather cap

[Jim Adney]

On 23 Aug 2017 at 19:25, Bobsnotch at aol.com wrote:

> Yup, we killed 2 used starters going out and back to Colorado in the 
> type 34. I know the heat from Kansas probably didn't help, and it was
> very hot  in the car (116*F in the shade at 4:30pm). 

It's hard to see how any reasonable amount of heat would damage a starter 
that's not running, but the starter solenoids contain a large copper coil that 
will get hot from the environment and from engine/transmission heat.

When copper gets hot its resistance goes up.

When the resistance goes up it draws less current.

Less current means less magnetic field.

Less magnetic field means less force on the core.

At some point, the core won't move, and nothing happens.

In most cases, this all returns to normal once the starter cools back down. I 
don't know what happened to Bob & Sue's starters, but this is most likely. If 
they wore out brushes, then they must have been at the tail end of life 
already.

Adding a relay to the starter solenoid circuit is a way to reduce the 
resistance in the path from the battery to the solenoid. This can make up for 
the increase in the solenoid resistance. Some people find it useful, but in 50 
years of driving Type 3s, I've only had 1 instance where I had to let the car 
cool a bit before it could be restarted.

My experience, however, is only with 12 V cars. I think there's some 
evidence that a relay is more helpful in 6 V cars, where a bit of voltage drop 
is more significant.


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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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