My instrument lights have been "dim" a while. I have LEDs installed and half don't turn on consistently. I noticed an improvement when I installed the headlight relays, I assumed the voltage going to the instrument cluster lights also went up a bit.

I know there is a dimmer switch on the headlight switch. My headlight switch isn't brand new, but a few years old and still seems fine.

I'm assuming my issue is low voltage, getting to the LEDs.

Has anyone ever tried fixing that? Maybe putting a relay in? The dimmer switch would no longer dim, but it generally doesn't with (cheap) LEDs anyways. But it could be used to turn them on/ off (when it gets past the cutoff voltage of the relay).

Just curious of everyones thought on this.

 

LEDS do not need a relay, if the voltage is low, I would suspect the dimmer unit, or possibly a poor connection somewhere

 

Headlight switch is just the dimmer, right?

I know LEDs don't "need" a relay in the sense that they are low power but if a poor connection/ high resistance connection somewhere a relay would compensate by bypassing all of the plugs, 29 year old wires and running through a potentiometer (headlight dimmer), wouldn't it?

Searching the forums and internet - dim instrument lights seem very common. And the suggested solutions are always to replace the headlight switch/dimmer , but I seldom see reports by those having issues to confirm it fixed it. This has been happening since I bought the XJ and even happened since I replaced the headlight switch. If it's a poor / high resistance connection somewhere my alternative is to take everything apart, clean connections again, maybe get a new flexible circuit, and likely run new wires. Why not bypass a tonne of that work and splice in a relay if I measure low voltage at the source? Or is that no difference really to just running or splicing new wire?

 

I might be answering my own question a bit too.

If I splice in a relay, might as well just run fresh wires/ connectors unless there is a big voltage drop across the dimmer. Which I could imagine happening.

But if there WAS a big voltage drop across the dimmer, it might not trigger the relay. LED cutoff voltage might be similar to the relay switching voltage. So that may not work anyways.

But if there was a big voltage drop across the dimmer and if it was a systematic issue (like if headlight switches needed replacement every couple years) I could run the instrument lights off of the radio backlight relay and have the instrument lights just set to on/ off triggered with the headlights. Would bypass the dimmer switch completely.

Again, only if dimmer is causing a large voltage drop and isn't reliably fixed with new headlight switch.

And my issue is honestly, likely not the switch, but is probably wiring or connection somewhere else. Which I might as well just repair.

I just needed to talk this thru I guess!

 

Yes, but you'd be masking the problem. See my sig, #1.

 

I'm confident it's not my grounds. I maintain those frequently. The issue had been there the entire time I owned the Jeep including after maintaining all of my grounds and replacing power/ ground wires.

I'm generally on the same page as you; see my last post.

My thinking is that if the dimmer switch has a voltage drop that's systematic - like a design issue (including a design that's not compatible with new technology like cheap LEDs rith cutoff voltages) - then I would think a relay or /and bypassing the dimmer would be no different of a solution than the headlight relay kit that many of us install and not masking the problem, but fixing a design issue. Which again, I don't know if it a design issue actually exists. I was just spitballing.

But yes, if it's a poor connection, not clean contact or broken wire then I might as well just fix it without a relay. I don't see a relay helping in those cases and that kind of "repair" would annoy me (same as if I spliced a wire in under the dash to replace a broken wire without removing the old wires. It's just...wrong..).

But I think I should probably check my LED bulbs and determine if I need to find some that operate at a lower voltage. Even if I need to spend a few bucks each, take a hit on brightness or go with a more green, yellow or red hue , if it's an issue of having slightly lower voltsge than needed then getting LEDs that function at a lower voltage is probably the simplest solution. LEDs range - based colour and circuit design - some turn on at 6 V, some at 9 V or higher. I have blue LEDs which take the most voltage to drive. As I understand it, for bulbs with 3x LEDs you need 3x3 Volts minimum (possibly more depending on the circuit) to drive a blue LED. For say, red, that's 3x2 Volts. Or a bulb with only a couple LEDs on it could work at a lower voltage. While 9 volts should be no problem, it's possible the bulbs that I have a higher minimum than that, like day 10 or 11V, and that might be too much to demand from a 30 year old Jeep. *Shrugs*

 

Rather than rewiring or bypassing your current system based on a whole bunch of speculation, why don't you go in and actually measure the voltage drop across your dimmer and wire runs? That will give you a real answer. And rather than speculating about your LEDs, why not pull their specs to see if they have a high cutoff voltage? You installed the LEDs, right? So look up what you put in.

Seems like a dedicated hour or two with a multi meter will put you miles ahead of internet spitballing.

 

I'm sorry if this thread seemed like more than spitballing or if it wasn't welcome.

Yes all those things would happen and yes I am pulling specs in my LEDs like I said I would. But the company I bought them from did not provide the specs so this is much more time to find out (much faster to just buy one I can find the specs to).

Sorry for raising hypotheticals, vocalizing my hypothesis before testing and wasting everyone's time.

 

Keep things simple:CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE INSTRUMENT PANEL GROUND

NOVEMBER 17, 2015 SALAD 14 COMMENTS EDIT

The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼” or 5/16″ head on it.

This ground point is responsible for handling the ground circuit for the following items: Dome lamps, seat belt and key warnings, transmission power/comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.

The problem is that where the ground point is located does not share good contact with the chassis where the ground should be. The solution is simple:

• Make up a jumper wire with #10 gauge wire about 10″ long. On one end, crimp on a ¼” round wire terminal. On the other end, crimp on a 3/8″ round wire terminal.
• Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
• Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely. Use a coating of OxGard at all ground contact surfaces when attaching the screw and nut.

**Special note for Comanche owners: Make your jumper wire 12″ long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**

 

Thanks! I've been planning on doing something similar with the dash ground, but want to install a fuse panel down there for ignition switched auxiliary power. I have the circuit designed but I wasn't sure the best place to connect the the ground to.

If I run a wire of appropriate gauge from the ground terminal on the fuse box to the 8mm stud you describe above - will that still be an appropriate location for ground for the added load? I am still thinking of trying the dash ground to the fuse box/8mm stud you point out, so that will all be tied together.

I'm doing the fuse box quite soon so I'll give this added ground a try as a first step.

 

Have you checked the voltage on that circuit yet?

 

Not yet. I just finished tracing wires, probing and diagnosing another issue (which coincidentally caused the instrument lights to go out, due to a blown parking brake light fuse) so I have to get the wires and harnesses in the kick panel back together and tidied up. Once that's buttoned up I will try this.

 

Why I initially created this thread
Just to give a bit more context on where my head was at when I first created this thread, I had been googling the issue since I had just fixed another issue on the circuit that was causing my instrument lights to go out.

From my google searches, I was under the impression it was a common issue with the instrument lights being dim, and I could not see many solutions posted. This is why I was coming off, maybe a little hot, with specifically asking if anyone has done anything like a relay before (because, again I was under the impression this was a common issue that doesn't get resolved, and I was wondering if I missed some fix somewhere on this).

After this thread kind of went sideways, I pulled those searches back up and quickly threw them into a table.
I've only found a total of 17 issues in my google search (fewer threads, but often a number of people posting or highjacking those threads with their own issues) related to the instrument lights.
So not a massive problem. Enough for my google searches to have pages of results, but nothing nearly as common as the headlight issues or door lock/ power windows issues.

Since I had that in Excel already I threw together a few pie charts to visualize how the issues were distributed.



So based on this, most of the issues people have are due to the light just straight up not working. And the majority of those were due to a short and blowing the parking brake fuse (actually a similar issue to what I had just resolved). On top of this are posts of people just asking about LEDs, which isn't really an issue, but just seemed to pad my google search results.

So I was way off base in what I assumed the scope of this issue was. I thought it was something more widespread than it is and was just trying to collect information and ideas when I first created this thread.

I'm guessing others in this thread were aware that this isn't a common issue in itself, and I'm guessing that's why we were misaligned.

What I am actually doing about MY issue
Now, the thread is clearly turning into an investigation into my own issue.
I totally welcome advice on actually fixing it. And although maybe it wasn't obvious, I personally don't do anything without testing first. I am VERY thorough and structured. Just because I was raising a hypothesis earlier or spitballing doesn't mean I was going to jump into doing anything without testing. I just got finished with 2 days of tracing wires, and a few weeks ago spent a day cutting out and repairing other wiring problems from the PO of this Jeep. I have a multimeter and use it. I'm not some cowboy cutting up my wiring harness ***** nilly.

In general, this is my plan. I lay this out now (based on the pesky hypothsis I raised earlier in the thread) so I can just work through it in a structured way down in my garage. I don't like going in without a plan:

1. I've got to get most of the wires back in place after my previous repair. Mostly need to connect the connectors in the kick panel, tidy up fuses, etc to make sure that's all good before I try to diagnose another issue
2. It's happening anyways when I install my aux power fuse box so I might as well do it right away - I'll tie the interior ground into the M8 stud as Cruiser suggested. This will just be adding the ground, not adding the fuse box. I'm keeping it simple and one thing at a time.
3. Test voltages for the lights, and maybe continuity on the flex circuit (it tends to look tarnished).
4. Test continuity at the lights/ gauges to ground
5. If low voltage at lights, work backwards. Focus on voltage at headlight switch next and work backwards.
   1. If low voltage at headlight switch/ dimmer switch then look at replacing the switch (unlikely; pretty damn new switch but I would need to rule it out first)
   2. If low voltage behind headlight switch, then.. could be anything. Look through connections, clean connections, check for pinched wires, etc.
6. If sufficient voltage at lights, try other LEDs with a known min voltage

Seem reasonable?

So the question is:
What's a reasonable voltage to have at the light sockets? 11.5 V? More? Less? When should I start looking at the headlight switch?

 

That would be a good place to have a relay triggered by the ignition and a dedicated power wire from the battery. The ignition switch and wiring is marginal for the amount of power going through it already.

 

Yup. That's exactly my plan 🙂