mattchan99

I believe I am having a problem with my new AEM analog boost gauge. During idle it is reading 0 to +2 psi and reading all the way to 35 psi on full throttle and on accelerator lift off it only vacuums down to -2 psi before it idles back above 0 psi. This gauge will always read positive boost but won't vacuum correctly. This is the -30psi to +35psi analog gauge. Can some one diagnosis this problem as the gauge itself. Also I have a Greddy Informeter that reads off the OBDII and it properly shows vacuum during lift off and idle. It shows it vacuums to -12.7 psi during lift off which is the max low on the reader and idles at -9 to -8.7 psi. I doubt it's the line I tapped into, I used the guide on evom forums. This is where I tapped right at the BOV line. Could this be a gauge calibration issue or sensor problem or both. I doubt it's wiring or voltage level from the fuse box.

AWDTerror

iTrader: (2)

Probably the sensor, I'm having to send my gauge back for the same symptoms, and I'm pretty sure it's the sensor(sending unit).

mattchan99

So your thoughts is the sensor. How are you replacing it? Did you send the sensor only or the whole entire package with both the sensor and gauge back to AEM directly through warranty or from the shop you brought your gauge from. So you think the gauge is not the root cause of all of this, like when I turn it on it does the full start-up check and sweep to -30 psi before situating at 0 psi and that is before I even turn on the engine so it looks like it zeroes out just fine. But when the engine is on it's a different story as it does go to vacuum state (negative psi zone).

stokEd

iTrader: (3)

Where are you taking power from? Does your gauge turn off when you start the car?

I had the same problems as the OP and it was a power issue. My switched power ( think I was using the cigarette lighter fuse) was cutting out when I started the car, shutting the gauge off momentarily. The gauge is setup to re-zero itself when it powers on and thus would show 0 psi at idle.

stokEd

iTrader: (3)

The solution is to use an uninterrupted power source for your constant and switched power.

I think my constant is from the sunroof fuse and I forget where I tapped into for switched power. I tried nearly every fuse in the fuse box before finding one that would work.

I can post up where exactly I'm getting power from tomorrow when I've got my car.

mattchan99

OMG you will be a god if you can fix this issue. Someone else also mentioned that on another forum but I did not understand what he mean. Right now I do noticed that when put the car on HOT which is key turned in one position to power the accessories, it's on but again when you full turn to ignition the gauge power shuts off and then turns on again when the car ignites. Can you take a pic of your fuse box setup so I can tap properly. Right now I did cigarette lighter. My wiring setup has both the constant and switch source wires into one connection.

stokEd

iTrader: (3)

Cigarette lighter fuse cuts out when you start the car so you'll need to get power elsewhere.

Sure thing. I'm out of town right now though, so it'll be tomorrow evening before I can get a picture up.

mattchan99

Yea I just noticed that. I have the 2 red wires which is the 12v constant connected to the dome lights and the pink wire + gray wire connected to the cigarette lighter fuse as the ignition switch to start the power but the problem like you state when you turn the key it cuts the power out and back on as the motor tries to turn over. I just tested my boost gauge by connecting both 2 red wires, pink wire and gray wire to constants and when I turn on the car it didn't cut out and properly displays -18psi during idle. Is that the correct vacuum reading for idle?

Also, however you setup your boost gauge for constant power and switch power, do you also setup a A/F (UEGO) gauge the same way?

On the side note, I blew a 10amp fuse when I tapped the sunroof for constant power haha but I have yet to blow the dome light one which I am tapping to now.

stokEd

iTrader: (3)

I think the gauge reads in inHg (inches of mercury,) but yes, 18-20 inHg is what you should expect.

Yes. I have the Analog Boost and UEGO and both are tapped into the same power. In fact, both gauges use the exact same wiring harness for power.

Oops. I guess I should have asked, do you have a sunroof?

mattchan99

Cool I can't wait till you get back home to take a pic of your fuse box setup. I already know that the gauges work now, it's just the power source for the switch operation is what i need. No my car is not equipped with a sunroof.

stokEd

iTrader: (3)

Working on it now.

mattchan99

good to know.

stokEd

iTrader: (3)

For my AEM gauges:

Fuse 3 - CONSTANT Power
Fuse 12 - IGNITION Power

stokEd

iTrader: (3)

In case you want/need to try other fuses for power:

tephra

iTrader: (6)

sounds like psia vs psig