I have an AEM X-Series 30-0306 gauge that finally figured out why erratic readings.

Was noticing at idle on startup and a while after is around -17, -21 or so coasting/engine braking.
But after well warmed up, more so on hot day is idle at -24 and -28 coasting.
But today after a drive I noticed when engine off, key still in it was -7 Vac? Unplugged hose
and the same. Let it cool down some and was -5. After a few hours when cool was at 0.
So of course my boost readings are all over the place.



Seems the sensor is affected by heat.....Guess I should not of mounted in engine compartment on firewall.
Will need to find coolest place inside, without routing too much hose or wire.
Behind glove box area somewhere out of the way.

Anyone else have one of these or an electronic gauge?
Where is your sensor mounted?

 

I used to have one of these , and I've experience the same issues as you.

I've changed the sensor 2 or 3 times which were only lasting about 4 months in summer heat.
Mind you I live in Canada and the summer here are way cooler than most state of America.

When you add the cost of buying the sensor 2 or 3 times and you start to realise that a basic analog Autometer boost gauge goes for only 10 more bucks than a AEM sensor the solution is pretty obvious.

Long story short put that thing in the trash where it belongs and buy an Autometer

 

Yeah, I am leaning towards replacing with an analog. Do miss the sweep of needle vs digital.
Today I did move sensor to inside, temporary setup. Seems more consistent reading on a short drive.
But was at -7.7 vac after parked with engine off, key still on. A few hours later back to 0.

 

I have the same unit and live in Canada. Have not noticed this issue mine is mounted under the steering column. I will pay attention to it thought if multiple people are reporting issues.

 

Now I recently heard possible altitude issue also....if not going back to zero when off...above 6000 ft. So that may of been part of it also?