Date:         Thu, 5 Jul 2001 17:05:16 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: headlight problem and "bad "grounds. SVX
Comments: To: pensioner <al_knoll@PACBELL.NET>
In-Reply-To:  <001201c11de4$64285b80$14a6fea9@900b>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 03:25 PM 8/5/2001, pensioner wrote:
>Bad grounds.. contrary to info presented on the list.  A bad ground will not
>cause a switch to overheat.  Overheating switches are caused by contact
>resistance at the high current contacts in the switch.  The dimmer

Right (as you know).  To amplify a little, the total power dissipated in a
circuit gets distributed proportionally to the resistances in the
circuit.  In a headlight circuit you ideally want zero resistance
everywhere except the headlight filament, in which case all the power would
go there.  In an actual circuit you have resistance in the wires, the
crimps, the push-on terminals, the switch contacts, all of which dissipate
power, i.e. heat up.  A higher-than-normal resistance anywhere along the
circuit will cause that part to heat up more than expected.  This causes
things to melt, and makes the headlights soggy and hard to light.

As the rogue resistance goes up and up and up, the total power dissipated
in the circuit goes down, so eventually you reach a point where nothing
overheats (but the lights don't light either).

david


David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"