Help needed. Boost gauge install... the electrical part!

SnakeMedic

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Admittedly I suck at electrical - home or auto. I have no idea why. People try to explain it and I just forget it.

Anyways, going to be putting a boost gauge in and just wondering best spot/way to tap into the power for the lighting on it. I assume tying it to the gauges, but where is the best access to do this? (I also am not 100% sure on where to tap into the vac lines, but that is a different story, LOL).

Yes, I know. I am a total noob when it comes to installing a boost gauge. Never done it before!!!

Thanks for any help/advice! I did try a search, but either it must not be the right way to search cause I could not find anything concrete.
 

mcglsr2

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It's really not that bad. I'm assuming your car is a 98 based on your sig - I've got a 95, so I won't give wire colors and stuff because I don't know if it will be different for you.

Is your gauge lit by LED or a normal bulb? Wiring it will essentially be the same, but you should be aware that if it's an LED gauge, it might not dim like the rest of your gauges. Not really a big deal, just a heads up.

Where are you installing the gauge? A good place to tap off for lights is right at the light switch knob. Under the dash there will be a wire that will carry the voltage for the lights when you turn the lights on. Just tap off that wire, to your gauge. If you want a different place, then anything that comes on in your interior when the lights come up will work - like if you have +12v accessory/cigarette lighter things that light up when the lights are on, you could tap off that as well. It depends on where you want to install the gauge, but I personally recommend right at the switch.

Vacuum/boost is also pretty easy. I'm assuming your gauge is mechanical (it came with a white/clear nylon tube that you are supposed to hook up) - if your gauge is electrical then the process will be different. Under the hood, just find a good source of vacuum/boost. Typically, the best place to hook into is at the intake manifold. There should be several lines coming out from this guy (hooked up on the underside, I believe), pick one of those and Tee into it.
 

SnakeMedic

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DANG.

Thanks for the info. Yes, it is mechanical. No, it is not LED. It will be a pillar mounted gauge, so pretty close to the light switch.

You make it sound so easy. I am sure I will mess it up the first try somehow. LOL. Time will tell!!!

Thanks again!
 

mcglsr2

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DANG.

Thanks for the info. Yes, it is mechanical. No, it is not LED. It will be a pillar mounted gauge, so pretty close to the light switch.

You make it sound so easy. I am sure I will mess it up the first try somehow. LOL. Time will tell!!!

Thanks again!

Nah, you got this. The absolute hardest part of the whole thing is finding that wire you want and then splicing in to it - and that's not that bad. Once you've done that, the rest is even easier.
 

kb1982

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If you pull out the headlight switch , and disconnet wiring harness connector, you will see the top pin that is closest to you. That pin supplies power to the dash indicator when the switch in on, with the cool dimming crap and all. You could tap into that wire, which is what i did with my autometer boost gauge thats is on the a pillar. Most gauges say not to connect them to the dimmer, but all of 5 of my autometer gauges are and it doesnt hurt anything.
 

ttocs

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funny wiring is the part that has never scared me.

I can't say I would recommend tapping any extra powered items to the headlight harness as it and the switch are known to be a weak point in the electrical system that will melt when it pulls too much current.

You are literally 8" above the ignition harness and with a test light/meter you can find the wire in 5 secs and it has plenty of extra power to supply things.
 

mcglsr2

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funny wiring is the part that has never scared me.

I can't say I would recommend tapping any extra powered items to the headlight harness as it and the switch are known to be a weak point in the electrical system that will melt when it pulls too much current.

You are literally 8" above the ignition harness and with a test light/meter you can find the wire in 5 secs and it has plenty of extra power to supply things.

I believe he was looking for a wire that carries voltage when the lights are on; not a wire that always carries +12V. Unless I mis-read the original post.
 

kb1982

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funny wiring is the part that has never scared me.

I can't say I would recommend tapping any extra powered items to the headlight harness as it and the switch are known to be a weak point in the electrical system that will melt when it pulls too much current.

You are literally 8" above the ignition harness and with a test light/meter you can find the wire in 5 secs and it has plenty of extra power to supply things.

Really isnt any other way around it if you want your gauges to light up when you turn the headlights on. The bulbs from autometer usually are 2.4 to 4.9 watts, not a lot. The way the switch is designed, you cant use a relay that closes when grounded, and a relay that uses power from the switch would draw as much as the light bulb.
 

SnakeMedic

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If you pull out the headlight switch , and disconnet wiring harness connector, you will see the top pin that is closest to you. That pin supplies power to the dash indicator when the switch in on, with the cool dimming crap and all. You could tap into that wire, which is what i did with my autometer boost gauge thats is on the a pillar. Most gauges say not to connect them to the dimmer, but all of 5 of my autometer gauges are and it doesnt hurt anything.

This is what I was thinking. You don't happen to have a picture of this, do you? Just to make sure I don't misinterpret which wire you mean and completely screw it up!!

funny wiring is the part that has never scared me.

I can't say I would recommend tapping any extra powered items to the headlight harness as it and the switch are known to be a weak point in the electrical system that will melt when it pulls too much current.

You are literally 8" above the ignition harness and with a test light/meter you can find the wire in 5 secs and it has plenty of extra power to supply things.

Really? It was my understanding (which is definitely very limited) that one gauge light won't draw much of anything and should not over match it and melt. Interesting....

I believe he was looking for a wire that carries voltage when the lights are on; not a wire that always carries +12V. Unless I mis-read the original post.

Correct. I just want it to come on when all the other gauges are on. I can't imagine I am the first person to do this...

Really isnt any other way around it if you want your gauges to light up when you turn the headlights on. The bulbs from autometer usually are 2.4 to 4.9 watts, not a lot. The way the switch is designed, you cant use a relay that closes when grounded, and a relay that uses power from the switch would draw as much as the light bulb.

That is what I thought. Not a whole lot of current drawing for a gauge light. It is an autometer.

Hmm.
 

ttocs

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your absolutely right that one gauge should not over load the circuit but the circuit is known to get hot/melt even with out anything else hooked up to it. I know more then a few people that had to replace the harness and the switch for no good reason. Again the ignition harness is only a few inches away and is really the correct way to wire into it.
 

kb1982

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Your headlight switch connector is gonna melt anyways sooner or later. It was just a poor design by FORD. The wiring was to small of a gauge. If you do get a replacement pigtail, they are larger gauge wires. Hell, the switch coulda been made to carry very little power through it if they would have used relays, or power was distributed directly to the lights from the fuse box and then the switch just grounded the circuts. But enough rant. The first picture shows the switch as how it is mounted in the car. The switch labeled I is the one that has the rheostat on it, and allows dimming of the dash lights, which will dim yur guages as well if hooked into it. Like I said previously, some guages say not to hook it into a rheostat, but im not sure about your gauge, heck im not sure about mine even, but it is hooked into it, and dims with my dash. My oil pressure gauge,boost, water temp, voltage, and tach all have the lights powered off of I. Every gauge i have ever hooked up in all my vehicles have been wired to the rheostat, but then again Ive never used any gauges that had led bulbs or hids or anything funky. The second pic, is the same as the first, just flipped for easier reading. And the third, is a burnt connector, that happens without anything extra wired in.


 

mcglsr2

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Yup, use "I" from above - though it's actually a 1, not an I ;) As said, it's dimmable, and will go into a fuse (#13 on the interior fuse panel, 10A). You can either wire in the gauge light before the fuse, but I'd recommend doing it after the fuse so you pick up the benefit from it. Your single gauge bulb should not affect it/cause it to blow. The wire color coming out of the light switch connector *and* out of the fuse panel is Light Blue w/ Red stripe.

ttocs, he can't use the ignition harness (I'm assuming you are talking about the ignition switch harness) - what wire on that harness is for lights?

Edit: Oh, and LED gauges will most likely draw even less current than their incandescent brethren - there's nothing wrong with using LEDs. In fact, all my gauges are LED ones, not the normal bulb kind. No problems.
 

SnakeMedic

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Ah! Thanks for the pictures! That is what I was wanting. I think even I couldn't screw that up!

Now.... I just gotta find the right vac lines to tie that into and I am golden!

Thanks everyone for the help. Certainly improving my knowledge!!
 

SnakeMedic

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Think I found the right vac line. Comes off the SC and into a t before hitting the plenum/intake. I could t off of it before it has a t. Shouldn't be a problem there at all. Now getting the tubing into the passenger compartment. You guys just cut a little hole in the existing grommet?
 

mcglsr2

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Think I found the right vac line. Comes off the SC and into a t before hitting the plenum/intake. I could t off of it before it has a t. Shouldn't be a problem there at all. Now getting the tubing into the passenger compartment. You guys just cut a little hole in the existing grommet?

Yup. It's even easier if you access to a tool like this - it's great for running things like your boost host and wires through grommets. If you don't, then just poke a tiny hole and force the tube through. If the tube isn't quite strong enough and it wants to bend before going through the grommet, tape it to a coat hanger and use that to help.
 

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