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sbchero
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Last seen: 5 months 2 weeks ago
Joined: 05/30/2019 - 09:03
30-0306 boost gauge not reading 0 at rest

I have a 30-0306 boost vac gauge and when the engine is off or its even off just in the air it reads -4.7 vac.  i had sent it in to AEM (sensor and gauge) and was deemed working.  get it back and same thing.  I live near denver @ 5100 feet ASL.  its wired to ign on and on while cranking.  does the sender need to be grounded?  i currently have it connected remotely with a vac hose.  

not that i want to or should have to with a $200 gauge but is there a way to set zero or trick it to read zero with engine off?  

AEM_JG
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Last seen: 20 hours 29 min ago
Joined: 06/03/2016 - 08:12
The sensor in the kit is a

The sensor in the kit is a MAP sensor, which reads the pressure relative to sea level. Since you are at 5100 ft with a barometric pressure of ~85 kPa, the gauge is reporting exactly as it should. 4.7 in Hg equates to ~16 kPa, subtract this number from 101.3 kPa (baro pressure at sea level) and you have 85.3 kPa or 4.7 in Hg. Rest assured that the gauge will operate as normal with the engine running, reporting the correct engine vacuum and boost for your conditions at that altitude.

sbchero
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Last seen: 5 months 2 weeks ago
Joined: 05/30/2019 - 09:03
well that good that the gauge

well that good that the gauge is accuate but it still doesnt help as im not going to be doing math as im glancing at the gauge while im driving to get a reading.  guess ill go with a different manufacturer for my guages.  

AEM_JG
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Last seen: 20 hours 29 min ago
Joined: 06/03/2016 - 08:12
There is no math needed, the

There is no math needed, the gauge will report your intake manifold pressure accurately while the engine is running. The engine off value reports the ambient atmospheric conditions, which in your case, is 4.7 inHg.