My vacum stays between 19-21in hg normally depending on the weather but everytime i turn on my headlights it comes down almost two points (usually to 18). is this normal? I really dont see how/why this could happen given its a mechanical gauge.

also how the f**k do you spell vacum/vaccum/vacumm, doesnt look right

 

vac·u·um (vky-m, -ym, -ym)



[Modified by DeepSi, 4:55 PM 2/15/2003]

 

mine does the same....usual

 

so its not just me. why/what could cause this though. engine not propertly gounded, bad alternator?

 

load on the engine....causes a voltage drop.......
same thing happens if you step on the brake...lights dim for a second....
the load drops the engines rpm a tad causing the vacuum to drop.....

btw it's spelled v a c u u m.........