VDO boost gauge showing 2" of vacuum when car off, problem or normal?

[EdwardNorth]

Hey all,

My boost gauge is showing 2 inches of vacuum (first tick mark) when the car is off. It is a VDO boost gauge. What I am wondering is, does this mean that the needle is out of calibration and it is indicating improperly when the car is on? For example, one tick mark in boost is 1 PSI, but the same tick mark in vacuum is 2 inches. Am I indicating 1 PSI too low in boost? Or is it normal for these gauges to be slightly off when the car is off? My Autometer boost gauge on my FD shows dead centered at 0 when it is off.

Also, the gauge always shows about 20-21 inches of vacuum for my Talon at idle.

Thanks guys!

 

[Coup D E'Tat]

My VDO is the same way, and I'd also like to know this.

 

[Defiant]

Until you get into the more expensive devices, Bourdon tube gauges are only good approximations. If you want to fuss with it, hook it up to a MityVac with a couple of other gauges and find how close it is.

You can try to get it zeroed by twisting the mounting nut on the back, where the vacuum port enters the body. Go gently but firmly. You're trying to move the whole guts of the gauge.

 

[Maranello993]

Hey, if you could be more specific on how to do that adjustment it would help a lot. I accidentally pulled my boost signal off when putting my wideband gauge in and while putting it back on, it messed up even more. It used to read 1 tick mark low when the car was off, but now it reads TWO and when I moved it around more it is almost THREE tick marks too low, 6" Hg. I really want to get this fixed so I can quickly and reliably read the gauge. The only things on the back of the gauge are the two electrical inputs for the bulb and a boost fitting that seems to be glued or something. Should I twist the base (it's hex shaped) with a wrench? It seems that the more I mess with it, the more it goes down.