Re: [Amc-list] F('ing)ailing parts 2

[Keleigh Hardie <keleigh3000@xxxxxxxxx>]

OK, I'm familiar with one such application. VW/Audi cars in the mid to 
late Eighties had two switches. A normally open switch that closed at .6 
bar, (hooked directly to the light, it worked just like you're used to) 
and a normally closed switch that opened at 1.8 bar and was monitored by 
a electronic relay that turned the light on and made a terrible screech 
if the switch opened above 1500 RPM. These things were notorious for 
intermittent random activation, and nowadays if you open the relay on a 
lot of these cars you'll find someone had broken the circuit board out 
of it and tossed it (the low pressure switch would still work normally 
if you did this). Don't ask how I know  ;)

Keleigh

Swygert, Francis G MSgt 436 CES/CECM wrote:
> Date: Wednesday, March 7, 2007 12:19 PM
> From: Keleigh Hardie <keleigh3000@xxxxxxxxx>
>
> One small nit:
>
> "An oil pressure switch closes the contacts as soon as the engine is
> started and the contacts stay closed until the engine is shut off."
>
> Most standard oil pressure switches are the other way around, I think.
> There is power to the light whenever the key is on. If there is no
> pressure, the switch is closed, grounding the light and turning it on.
> When you  start the engine the pressure opens the switch, removes the
> ground and turns the light off. Only if there is a relay or electronics
> involved do they work the other way around...
> ----------------------
>
> And I agree with you Keleigh! But this particular switch, which is
> spec'd as an oil pressure switch in some application (don't know what!)
> works in reverse. Contacts are normally open, and close under pressure.
> It's not a typical US oil pressure switch, must be a foreign application
> -- or an obscure/old US application. It's been *mistakenly* cross
> referenced as a substitute for the pressure type brake light switch.
>
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