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1991 Cherokee Laredo, 3.5" Rubicon Express lift, 31" BFG Mudders, Smittybuit F/R Bumpers...
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Discussion Starter · #1 ·
So, I decided to pull the dash gauge cluster out and replace all the bulbs with red LED bulbs as they generate less heat, are more power efficient, and I like red interior lights at night.

But, the back of the dash doesn’t show polarity on the Mylar traces so I was not able to determine accurately which trace is positive and which is negative. For incandescent bulbs it doesn’t matter, but for LEDs it does. When I put the dash back in and tried testing I immediately blew the console fuse (7.5 amp). I tried this process four more time and finally gave up and put the old bulbs back in.

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229504


I have original Jeep shop manuals for the ‘91 but following all the schematics is beyond my capabilities…

Does anyone here have experience with this kind of upgrade?
 

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I haven't done the upgrade, but I do have some experience with the dash. So you need to find the ground and positive?
 

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1991 Cherokee Laredo, 3.5" Rubicon Express lift, 31" BFG Mudders, Smittybuit F/R Bumpers...
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Discussion Starter · #3 ·
For the main cluster I was able to use a multimeter to identify, what I thought, were all the grounds. I then oriented the bulbs in what I thought were the correct positions. For the smaller bulb area (left side sitting at the wheel) that was not possible. So I tried using the schematics to identify positive and negative. But, in four tries, I was not able to get it to work. I’d reinstall the dash, reconnect the battery, and then start the engine. Every time none of the gauges worked and the dash fuse blows.

I’d expect that the LEDs simply wouldn’t light up if the polarity wasn’t right so I’m not sure why the fuse is blowing. But, swapping back to incandescent bulbs fixes everything… very strange. And I can’t imagine that the LEDs are pulling more power than the incandescent bulbs did, but maybe…
 

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They shouldn't be. But, if you don't use a resistor in things like tail lights the flasher won't work right. The grounds if you follow the copper ribon on the back wull be the ones that go to multiple bulbs. For instance, on the left side in your pic it is the one shared by the dash light and far left signal light. All the rest in the main dash share the same ground that goes all the way around from the left to the right side and back to the plug. On the idiot light side, grounds are also shared, but not all of them share that ground. It depends on what the lights indicate
 

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I installed a kit a few years ago from OneWayLight. When I put the LEDs in the dash, it was a game of guess and check. Never blew a fuse, the LEDs just didn't light up until they were in right. Never had an issue. Of course LEDs have come a long ways in a couple years so things may have changed, but the ones I used are great. They even dim a little when using the dimmer switch.

Might look into other types or manufacturers for yours. Some have built in resistors and some don't (or at least the didn't). Good luck!
 

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And your question is?
 

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1991 Cherokee Laredo, 3.5" Rubicon Express lift, 31" BFG Mudders, Smittybuit F/R Bumpers...
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Discussion Starter · #8 ·
Not sure who the “and your question is” is directed at, but I’ll assume me…

I didn’t really have any question beyond the original info. When I tried to install replacement LED “bulbs” into the instrument cluster I was not able to easily determine which trace on the “board” was positive and which was negative. Several were obvious and tested out fine using my multimeter, but others were not. And strangely, the cluster fuse blew every time I connected things back up. So, I just put the old bulbs back in and stayed incandescent.

The question, if I didn’t directly ask it before, would be, why would using LEDs (polarized) cause the fuse to blow? I’d think the worst case would be some LEDs simply wouldn’t work if they didn’t get put in the socket with the correct polarity. I did not expect to blow a fuse. Resisters would be required for the signal bulbs, but I don’t think they’d be needed in the cluster.
 

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It wasn't you MadMacks, it was to lurddab. He quoted me and had nothing after the quote. Just trying to understand his message
 
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