MASTER - parts cross reference list

[content22207_2]

Right. But now the external housing would be positive, meaning that it can short out much easier to blow a fuse by simply touching it.

Evaporator box is made of plastic -- non conductive (just like the car itself...).

Plastic evaporator box mounted to a fiberglass dashboard -- I'm good.

Bill Robertson
#5939

[content22207_2]

Right. But now the external housing would be positive, meaning that it can short out much easier to blow a fuse by simply touching it.

Exactly what does Robert think happens if you touch a power wire to a negative ground housing?

Tomato tomato....

Bill Robertson
#5939

[Josh]

Right. But now the external housing would be positive, meaning that it can short out much easier to blow a fuse by simply touching it.

I agree, electrifying the external housing is kind of dumb.

but i dare not challenge the genius that is bill...

[content22207_2]

Um, negative *IS* electrified. In fact that is the source of DC flow -- current flows from negative to positive (Ben Franklin got it backwards).

In the late 40's/early 50's some car companies went through a phase of trying to sort everything out with positive grounded vehicles, but they never caught on.

On a metal bodied car current flows through the entire car structure back to the battery. Works much better than DeLorean's daisy chains of ground wires.

If you ever wonder why steel fasteners weld themselves to your PRV, it's because the engine is electrically charged all the time. Add moisture and the dissimilar metals become miniature batteries, sharing electrons until they become one.

Irrespective, the evaporator box is electrically neutral because it is non-conductive, just like the plastic distributor cap that insulates ignition voltage from the negative grounded distributor body.

Bill Robertson
#5939

[Farrar]

In the case of the blower motor, you wouldn't be blowing a fuse, anyway -- just tripping the auto-reset breaker. If nothing else, that would make troubleshooting easier...

[content22207_2]

This whole tempest in a teapot is nothing more than a controversy in search of a crisis. There is no difference between touching a positive lead to a negatively grounded frame and touching a negative lead to a positively grounded frame -- effect is exactly the same: a short circuit (objective is not to touch either...).

If the evaporator box itself was negatively grounded then there would indeed be a problem because a positively grounded blower motor frame would essentially be a giant positive lead. But the evaporator box isn't grounded -- it's a big piece of electrically neutral plastic. Moreover, it is attached to an electrically neutral fiberglass underbody. Without a complex web of ground wires, the entire car body is electrically neutral for crying out loud (try disconnecting that bolt behind the parcel shelf and see what happens...).

Bill Robertson
#5939

[Farrar]

a controversy in search of a crisis

Isn't that what the internet is for?

[Josh]

I dont need a lecture on DC circuits.
As mentioned it woudnt make much to ground out the casing and trip the fuse / breaker.
How about if your evaporator is leaking or the drain tube is plugged. Seems like a bad time having water contacting the casing.

Anyway i'm done with this. The only opinion you value is your own, as you are the all mighty bill.

[content22207_2]

Everybody running around with their hands in the air does realize that a traditional steering wheel with integrated horn is positively charged all the time? (Not the non-conductive ring you hold onto, but metal superstructure inside the horn portion is charged just waiting for you to mash it against the column ground).

Bill Robertson
#5939

[content22207_2]

the all mighty bill.

Is it possible your personal prejudices are interfering with technical discussion?

Bill Robertson
#5939