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Old 05-07-2003, 10:24 PM   #1
latinskllz
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Default Using a 30amp Bosch Relay STDP to connect four Greddy Gauges and TEC-II Switched 12v.

I have three Greddy 52mm gauges and a Electromotive TEC-II Engine Management system. I was thinking of using this schematic for wiring my gauges and the source for 12V switched for the TEC-II:

Notes:

- All three gauges are electronic and need : 12v constant, 12v switched, ground, and illumination. The wire size of the gauge harness is about 22-24awg.
- The TEC-II has two wires coming out : 12v constant and ground. The 12v constant needs clean DC power( so this is going to the positive batt terminal.) The Wire Size is 10awg.
- The 12v Switched that the TEC-ii needs comes out from the harness connector and uses 18 gauge wire.
- The TEC-II current draw is between 6-12amps depending on number of cylinders.

Here's the schematic:

I bought a 100 watt amp kit from a audio shop here that has a loom of 16ft power wire with a inline 30amp fuse using 10awg power and ground wire. It also comes with 10ft of 16awg speaker wire.

I was thinking of using a relay (SPDT) bosch 30 amp to power the 3 gauges and later on an extra gauge as well as supply the 12v switched for the TEC-II. If I understood the Relay schematic, I could wire as follows to the relay:

1) 10 gauge power wire with inline fuse from battery positive to the 30 (before connecting this to the relay, tee off the power wire to the dash to supply the constant 12v for gauges.
2) ground the relay by connecting 10 gauge wire to good ground connected to 85
3) find the ignition harness which is 10 gauge size and solder 12 gauge power wire to it and route it to the 86
4) run a 10 gauge power wire from the 87 to the gauges(including the TEC-II 12v switched) and connect all four gauge 12v switched power wires to this single 10 gauge wire

Now all I have to do is find the illumination wire and tap into that for all the gauges and then find a common ground for all the gauges and connect the ground using 10gauge.

The length of wire used in each step above will be approximately:

1) from battery to the relay: 5ft --------- from the tee to the gauges--------2ft
2) max 3ft
3) 3ft
4) 2-3ft

How does this schematic sound? I am having trouble finding info on the current draw for the gauges, but I suspect it to be no more than 1amp each?

Any insight is greatly appreciated...the 10 gauge wire may be too thick to run these items but I wanted an experts opinion.

I don't want to tap in different areas for my gauges.

Kevin
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Old 05-07-2003, 10:33 PM   #2
tdxflex
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the 85 and 86 terminals on the relay don't need big wire, probably only need 16ga there. the point of a relay is to use a small current source to control a larger one. the main current is coming from the 30 to the 87. the wiring is right though, 85 ground, 86 ignition controlled, 30 battery with fuse, 87 to your tec-ii, gauges, and anything else you need ignition controlled power for, as long as current stays under the relay's specs in this case 30amps. the gauges don't pull a lot of current, you can just tell by looking at the size wire they come with stock. there's probably something about exactly how much in the manual. 30amps for a few feet, i'd say you'll be more than safe with 10ga wire for the 30 and 87 connections.
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Old 05-07-2003, 11:02 PM   #3
latinskllz
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Quote:
Originally posted by tdxflex
the 85 and 86 terminals on the relay don't need big wire, probably only need 16ga there.
Well the 12v ignition from the actual ignition harness is 10 gauge so that's why I thought about running 10 guage to the relay.

Is it ok to use 10 gauge on all the terminals on the relay and then switch to 16awg for each gauge and the tec-ii switched 12v?

Thanks for the quick reply man...should I mount the relay in the engine bay or inside the cabin by a bolt :P
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Old 05-07-2003, 11:16 PM   #4
tdxflex
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when you tap into the ignition wire, that length of wire to the relay will be so short, 16ga and 10ga will essentially be the same thing. also the relay will only draw <1amp between the 85 and 86 so that's all you need to base your wire size on.

i would mount the relay under the dash, probably use the least amount of wire there, and the just zip tie it to something. get the ignition from something like the key cylinder, you can ground on that bolt holding that metal plate that's supposed to protect your legs in a crash (you'll see a ground that's already being used there). so that's already <1ft of wire for your 85 and 86 terminals. go through the grommet above the clutch pedal to get ot the battery, maybe 3-4ft max, then to your gauges, can't be more than 2ft for each of your gauges and tec-ii. 16ga to each gauge is not a problem, for the tec-ii is just being used for the switched 12V? 16ga there should be fine also. all of the switched voltages are just controls so i think 16ga would be safe.

edit: totally forgot about the fusebox under the dash. you can use an empty one for your power instead of going to the battery. i haven't done any of this stuff in a while sorry about that. that should cut down your length of wire even further.

Last edited by tdxflex; 05-08-2003 at 03:59 PM.
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Old 05-08-2003, 12:00 PM   #5
Austin
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There's no reason to use your TEC output to power your gauges. Use it for something cool...

You can pull every type of power you need for your gauges off the fuseblock.
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Old 05-08-2003, 02:14 PM   #6
latinskllz
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Quote:
Originally posted by Austin
There's no reason to use your TEC output to power your gauges. Use it for something cool...

You can pull every type of power you need for your gauges off the fuseblock.
I'm not using my TEC Output to power....I'm just using a relay to have the source for 12v constant and switched....the tec-ii needs a 12v switched in addition to the 12 volt constant and ground...

Am I making sense out of this?

kevin
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Old 05-08-2003, 03:55 PM   #7
Austin
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Ah, I see... I misunderstood what you were saying.

You're saying you're going to use the same constant 12v, switched 12v, and ground connections for the TEC and your gauges, right?
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Old 05-08-2003, 05:33 PM   #8
latinskllz
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Quote:
Originally posted by Austin
Ah, I see... I misunderstood what you were saying.

You're saying you're going to use the same constant 12v, switched 12v, and ground connections for the TEC and your gauges, right?
YES! :P

Basically I want to run a 10 gauge power wire from the battery with an inline 30amp fuse to the relay, then basically power those things up from there :P

The tec-ii current draw is 6-12amps depending on number of cylinders....make sense? Do I have a valid schematic?
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