Batman33165

So i know this is an old thread on both here on this site and Jeep forum but i am hoping someone can enlighten me with some step by step pictures?

Before someone else post it, here is the link but the pictures are not working....
http://www.jeepforum.com/forum/f11/r...ge-fix-684375/

To my understanding:

1. Run a wire from either the battery or the starter motor relay to a relay

2. 30 power, 87 to gauges, 85 ingnition source, 86 ground

3. the wire from 87 goes to an inline fuse or just to number 17 on the fuse box with a 7.5 fuse?

3a. If it goes to the number 17 do i need to connect it to the back of the fuse box or can i wrap one side of the pins of the fuse and stick it into the slot 17?

4. Hopefully not set the jeep on fire

cruiser54

Pix work for me in the link...........

BlueRidgeMark

No no no no no no NOOOO!!!!!!

Let's think about why we use fuses in the first place. We don't want fires, right? And how do we start fires?

We let hot wires contact ground directly without a load (a motor, a light, or something like that) to restrict the flow of current. With no restriction, we get too much current for the wire, it overheats, and bad things happen.

Since this is never planned, in a perfect world, we'd never need fuses. But, we don't live in a perfect world and sometimes wires rub on metal parts, wear through the insulation, and we start heating up a wire, sometimes enough to damage things, sometimes enough to start a fire, and sometimes people even die. Electrical fires are serious business, and fuses and circuit breakers are there to minimize the chance of having electrical fires.

So, let's put a fuse in, shall we? But where?

As close as possible to the power source, of course! We want to minimize the length of any un-fused wire. The shorter it is, the fewer chances of it getting shorted to ground.

So, that connection from the battery to the relay #30 terminal needs to be fused as close as possible to the battery.

Once that lead is properly fused, do you need another fuse inline on #87? No, everything from the battery to the gauge is already protected by that one fuse near the battery feeding the #30 terminal.


I would not use more than a 5 amp fuse, myself. A volt meter isn't going to draw any appreciable current. A 2 amp would be fine, and the lower the better. The ONLY reason for using a 10 or 20 amp fuse is because you have a load that needs that much. You always want your fuse to be as small as possible to support the load that will be placed on it.

The other place you need a fuse is on the lead going from your ignition source to the relay, #85 as you described it. A 1 amp fuse is plenty. These relays only draw about a quarter amp for the coil.


That's a great way to wreck the fuse box. Never shove wires in next to fuses.

I'm not sure on your year Jeep if there are any sources of ignition switch power there. Some fuse boxes have an empty port where you can get switched 12v. If you can find one, simply use a pushed in.

Otherwise, use a piggyback fuse connector.

Hmmm. Do you have glass fuses?

Then use one of these:

Batman33165

I appreciate the lesson in electronics and wiring... So If i understood you correctly i would put a (very) low amp inline fuse from my power source to 30, then another (very) low amp inline fuse on the ignition side to the relay, ground, and then what to I do with the fourth wire?

That is why I was hoping for pictures on the link I posted first.

I think it might be easier to get some pods and attach some new gauges. One new one just dedicated to the battery

cruiser54

Have you upgraded your cables and done Tip 18?

http://cruiser54.com/?p=110

BlueRidgeMark

Just like you posted above!




30 comes from constant 12v, battery (fused). 87 goes to your gauge. 85 to an ignition source (fused), 86 to ground.

You are just using the relay as a switch to keep the voltage gauge from being ON all the time.

Take a look at these relay diagrams from www.the12volt.com (That's a great resource, BTW.)


A relay is just a switch. We use a small current to operate an electromagnet (terminals 85 and 86), which pulls a spring-loaded arm that makes contact between either terminals 30 and 87a OR between terminals 30 and 87.

The spring holds the arm against terminal 87a, so 30 and 87a are normally connected.

30 and 87 are normally NOT connected.

If we want to switch something on, we use 30 and 87 for our circuit, and when we want them connected, we apply 12v to 85 and 86. This powers the electromagnet, which pulls the arm away from 87a, and connects it to 87, which then provides power to ... whatever we want. Could be fog lights, could be an air horn. In your case it's a voltmeter.




You'll still need to have a relay to keep it from being on all the time.

djgrayxj

Note from DJ
I believe the industry protocol for relays is the coil connector 86 is positive voltage and relay coil connector 85 is the ground connection.

BlueRidgeMark

Thank for that, DJ. I know there's a convention, I just never remember what it is. My bad.

Functionally, there's no difference, of course, but its generally a good idea to follow conventions. Makes life easier for the next guy troubleshooting.

Batman33165

Yes sir Cruiser, was one of the first things i did when i bought the jeep. Helped the instrument panel a lot.

there is more grounding/ improvements elsewhere i need to do...

So besides the relay and wiring part, the 87 that goes to the gauges.... Am i splicing a wiring? Because i can not really run a wire straight to the battery gauge. Here i am showing for the plugs that go into the back of the instrument cluster, but i see nothing about the battery gauge.

BlueRidgeMark

Oh, well, that's fun! No hint of a voltmeter.

What's the source of the diagram? Field Service Manual (FSM)?

Or one of the Haynes/Chilton variety?

cruiser54

The diagram is for a 91 to 92.....

Batman33165

yea i did notice that also... i will have to continue and googling online for the connector and its wires