Which wires to use for boost guage?

shemoves · Post by **shemoves** » Wed Sep 07, 2005 5:50 am

I am going to install a Greddy electronic boost guage. I need +12V constant, Ignition, and light sources. Where is the best place to tap these?

rallysam · Post by **rallysam** » Wed Sep 07, 2005 6:17 am

I thought it was pretty easy to tap ON-12V and dimmer-12V from the cruise control switch and mirror switch. The nice thing is that it's close to where people mount gauges, and you can get to it without taking apart the dash - just pop out those switch panels carefully with a screw driver and there they are. I did this for my A-pillar install.

I don't remember which wire is which. I disconnected the connectors, turned on the car, turned on the headlights, and turned up the dimmer. Then, I probed around with a multimeter. When you find 10-14V between two of the pins, you need to figure out what type of power it is - so turn the headlights on and off, adjust the dimmer, turn the car on and off, and see if the voltages do what you want them to.

gt2.5turbo · Post by **gt2.5turbo** » Wed Sep 07, 2005 7:56 am

cig lighter is a good one too

shemoves · Post by **shemoves** » Thu Sep 08, 2005 1:38 am

does cig lighter have dimmer or just the swithced power and ground? Thx for the tip rally.

gt2.5turbo · Post by **gt2.5turbo** » Thu Sep 08, 2005 2:38 am

i know the ring around mine dims and i tapped into that

shemoves · Post by **shemoves** » Thu Sep 08, 2005 7:12 pm

good to know GT...I'll look into that. Would you be able to tell me where the vacuum tube is that I need to splice in to?

rallysam · Post by **rallysam** » Thu Sep 08, 2005 8:00 pm

DependS on what you want to know.

To read what the engine manifold sees, most people tee off a small vacuum tube that comes off the intake manifold. You'll find it coming off the manifold on the passenger side near the top. It runs over across the airbox and up to the pressure solenoid which is mounted to the passenger side strut tower. I tee'd there.

You could also tee off the compressor to see what it's doing. I think there's a pressure hose that comes off it, but I've never looked into that.

gt2.5turbo · Post by **gt2.5turbo** » Thu Sep 08, 2005 8:38 pm

thats where i tee'd mine off but i did it right next to the manifold instead of after the stock plastic tee that connects the line above to the line directly into the manifold. Oh and if you decide to use the cig lighter power source i found it easier to remove the stereo unit out completely to access the wires. and if your car is a automatic the best way to go through the firewall is to pull the dimond shaped gromet on your firewall and notch it to fit the line though.

shemoves · Post by **shemoves** » Fri Sep 09, 2005 9:30 pm

excellent. Is the grommet behind the pedals?

rallysam · Post by **rallysam** » Fri Sep 09, 2005 9:38 pm

That's where I went through, a gromet somewhere near the pedals. Just make sure any cables you route past the pedals are tied up out of the way... relialby enough so that it won't interfere with your pedal operation under any circumstances. Intefering with the operation of the brake pedal is obviously pretty dangerous.

shemoves · Post by **shemoves** » Fri Sep 09, 2005 11:41 pm

Edit...how do I get the stereo out?

gt2.5turbo · Post by **gt2.5turbo** » Sat Sep 10, 2005 12:32 am

pull the cup holder and the ash tray, undo the screws behind the cupholder and above the ashtray, undo the six screws around the stereo (one each corner and one on each side). unhook the connections behind the stereo.. and wala

shemoves · Post by **shemoves** » Sat Sep 10, 2005 12:36 am

how the heck to you undo the screws above the ashtray...can't fit a screwdriver in there.

shemoves · Post by **shemoves** » Sat Sep 10, 2005 1:05 am

alright, so it seem that using the side mirror wires will be easier. Now, when testing with a multimeter...do I just make sure the black piece is grounded and put the red against the lead? also, which setting...DC V?

shemoves · Post by **shemoves** » Sat Sep 10, 2005 2:06 am

alright, got everything I needed off the switches...except 12v constant...where might I find this?

rallysam · Post by **rallysam** » Sat Sep 10, 2005 6:33 pm

shemoves wrote:alright, so it seem that using the side mirror wires will be easier. Now, when testing with a multimeter...do I just make sure the black piece is grounded and put the red against the lead? also, which setting...DC V?

I assume you got this figured out? Just in case, the answer would be to move both the red and black probes around in different holes until you found 10-14V between any two pins (positive or negative). If it's positive, then your black probe is on ground. if it's negative, then the red probe is on ground.

shemoves wrote:alright, got everything I needed off the switches...except 12v constant...where might I find this?

You mean you want to have 12V on even when the key is turned off? Do you really need that for anything? I used 12V switched on and off by the key, and I found it in those switch plates.

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Which wires to use for boost guage?

Which wires to use for boost guage?