blowing "ign lps" fuse, can't figure out why - JeepForum.com
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post #1 of 16 Old 07-09-2020, 01:01 PM Thread Starter
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blowing "ign lps" fuse, can't figure out why

Hey all, thanks for any help you can provide. So, I just finished painting my jeep, and i had it all apart, including the dash completely out and disconnected everything. However, I was having some problems before, and I labeled everything and put everything back as it was before, so i think this is a preexisting problem from PO. It's had a nutter bypass so no computer or anything related. As title says, every time I turn the ignition i blow the ign lps fuse, which of course affects my gauges... I traced the small red wire coming from it and it goes to a splice of red wires, I think splice "R" on the wiring diagram (the version I have at least). It follows the wiring diagram, almost...one wire goes to fuel gauge, one goes to oil pressure gauge, and one goes to a light bulb, on the diagram the brake warning light bulb. On one of the wiring diagrams I have, there is another wire that goes to the quadratrac bulb, but I don't have that. Instead, one long wire goes all the way back to the fuse block, not to a fuse but to the backing plate that connects to the engine harness. This red wire is linked to another red wire that goes into the engine bay, but that wire is only about 3" long and is cut. However, I don't think it's related to that wire, as I actually just cut it near the spice (later reconnected it) and I still have the same problem.

It's difficult of course to show all this with pictures, so I have a pic of my new ice blue color mid-build, along with what my fuse box looks like. I've since changed the fuse amps to the correct values, e.g., Ign lps from 20 to 15 (was blowing out either way) and others e.g., the ACC was a 30 now it's a 10.

Anyone have a similar problem? What pics can I send? What can I do?

thanks,
Roy

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post #2 of 16 Old 07-09-2020, 02:00 PM
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Quote:
Originally Posted by royslaredo View Post
Hey all, thanks for any help you can provide.

So, I just finished painting my jeep, and i had it all apart, including the dash completely out and disconnected everything. However, I was having some problems before, and I labeled everything and put everything back as it was before, so i think this is a preexisting problem from PO.

It's had a nutter bypass so no computer or anything related.
The computer was powered by this fuse, was the computer harness removed?

Quote:
As title says, every time I turn the ignition i blow the ign lps fuse, which of course affects my gauges...
I traced the small red wire coming from it and it goes to a splice of red wires, I think splice "R" on the wiring diagram (the version I have at least). It follows the wiring diagram, almost...

one wire goes to fuel gauge, one goes to oil pressure gauge, and one goes to a light bulb, on the diagram the brake warning light bulb.
On one of the wiring diagrams I have, there is another wire that goes to the quadratrac bulb, but I don't have that.

Instead, one long wire goes all the way back to the fuse block, not to a fuse but to the backing plate that connects to the engine harness.
This red wire is linked to another red wire that goes into the engine bay, but that wire is only about 3" long and is cut.
However, I don't think it's related to that wire, as I actually just cut it near the spice (later reconnected it) and I still have the same problem.
Maybe this is the wire left over from the computer.
Make sure it's not pinched along the way.

Quote:
It's difficult of course to show all this with pictures, so I have a pic of my new ice blue color mid-build, along with what my fuse box looks like. I've since changed the fuse amps to the correct values, e.g., Ign lps from 20 to 15 (was blowing out either way) and others e.g., the ACC was a 30 now it's a 10.

Anyone have a similar problem? What pics can I send? What can I do?

thanks,
Roy
To save on fuses, You could plug in a 12 volt light into the fuse socket. When ever the light is on, you have current flowing. If it's really bright, you have a short.
The light bulb will limit the current so you won't melt any thing when it's shorted.

First thing I would do is disconnect the gauges. That would be the red wire attached to the "I" post on the fuel gauge.
These fuel gauges have been known to shift and short out to the speedometer housing when the cardboard insulators become cracked and crumbly.

Disconnect the oil pressure gauge also.

Check the harness to make sure it's not rubbing against something.


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post #3 of 16 Old 07-10-2020, 06:24 AM Thread Starter
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Thanks John,

"The computer was powered by this fuse, was the computer harness removed?"

... I wondered if that was it. Yes, the entire computer harness and computer was removed. I did the nutter bypass, and followed advice from this forum (which is great!). Still have everything in the basement.....

"Maybe this is the wire left over from the computer.
Make sure it's not pinched along the way."

....I've traced that wire from the "R" splice forward and back several times, and everything is in good shape not pinched or anything on the tub side. On the engine side, as I mentioned it's ~3" long and just cut. ....


"To save on fuses, You could plug in a 12 volt light into the fuse socket."

..... I'll try it. Would auto parts store have one that plugs directly into the socket, or do I have to wire it?....


"First thing I would do is disconnect the gauges. .....Disconnect the oil pressure gauge also."

.....Ok, I'll try it!

"Check the harness to make sure it's not rubbing against something."

Not sure what you mean here. Can you please be more specific. I guess you mean the wiring harness on the tub side of the firewall. It's all in pretty good shape. A couple of weeks ago I unwrapped the black tape from the loom so I could trace wires, and also cleaned things up a bit when I had it apart to paint the dash panel. most of it is in good shape, and where ever there was an exposed wire I taped it up.


thanks again!! I'll also take some more pics later today and post them....
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post #4 of 16 Old 07-10-2020, 08:26 AM Thread Starter
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Ok, update: I disconnected all the gauges, started.... fuse ok. Then connected in sequence the voltage gauge, oil pressure, temperature (on speedo housing) and finally fuel gauge, starting it between each connection. Only when I reached the fuel gauge did the fuse blow. I did rearrange some of the ground wires on the speedo housing this time (see pictures). could this be the reason? What next?

thanks!!!!!!!!!
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post #5 of 16 Old 07-10-2020, 09:41 AM
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Great pictures!

Is that a new fuel gauge?

There can be a couple things wrong with the fuel gauge.
It could of come loose and slipped a little and is now shorting against the speedometer housing. Thy wiggling it and see if itís loose.

It could be you have a full tank of gas and since you just painted the dash
, you have it hanging down so there is no ground connection so the regulator is not working and the gauge is pulling too much power. But Iím not sure it will be pullin >15 amps worth.

It could of also burned up inside and something is shorting out. You will have to check the resistance on the terminals to be sure.
There is a link in my signature that will give you the values it should measure.

Add a ground!!!
I canít emphasize that enough. Run it from one of the mounting posts that holds the speedometer in place. You have one there already but it may be ground for the dash lights.

c528116e-7261-41d0-bb4c-6b73058eaec7.jpg

Sometimes the harness can lay across moving items like the brake pedal and linkage or the clutch pedal and mechanism. Look in that area for wear.
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post #6 of 16 Old 07-10-2020, 02:33 PM Thread Starter
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Ok.... update. First, I wiggled the posts and nuts etc on the fuel gauge, no wiggle.. . That is the original fuel gauge, although I had it off b4, had installed an aftermarket one, and just put it back on / in b/c I liked the look better and thought it would work. It was working occasionally when I was playing around with the wires just a few days ago. I think it's still good and working, if I had to bet on it. .. next, I cleaned all the wires going to the post on the dash panel holding the speedometer, I ground off the paint (again) around the post, added grounding washers, and added a ground wire, which I connected to the same post and the other end into the engine bay and connected to the bolt post that the battery ground wire for grounding the tub goes on. .....but unfortunately, still having the same problem. With the fuel wires connected, the ign lps 15 amp fuse blows out. .. Could it be my dimmer switch, which I haven't connected yet and is just hanging and also touching the floor board... ?
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post #7 of 16 Old 07-10-2020, 07:17 PM
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No, It couldn't be the dimmer switch, That is on a seperate circuit protected by a Circuit breaker inside the headlight switch.

But you could of re-installed the fuel gauge at an angle. Easy enough mistake to happen.

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There are two little holes or divots in the speedometer housing that the gauge is suppose to be aligned with so it doesn't short out.

You might try loosening the nuts up and see if it drops into those holes a little better. Then tighten them back up.

Also try disconnecting the pink wire that goes to the fuel level sensor and the temp sensor wire on the temp gauge.


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post #8 of 16 Old 07-11-2020, 10:27 AM Thread Starter
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a quick update.. I took the speedometer out, and everything looks fine. Regardless, I took all the bolts off the gauge posts and wiggled everything around, and put it all back together. Then, the fuse did NOT blow out....but the fuel gauge isn't working. I have to let it run a bit to see if the temp gauge is working, and I'm gonna get a good voltmeter and check the gauge to make sure it's working. If not, I'll the "new" one back in......
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post #9 of 16 Old 07-12-2020, 04:40 PM Thread Starter
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Ok, I started the jeep and let it run and the T gauge was not working. I checked the resistance across the posts on the fuel gauge and to ground and they were all over the place and certainly did not read like they should have. So, I put in the other aftermarket gauges I had. Then, started it up again and fuel, voltage, and oil pressure gauge work, but now the temp gauge doesn't. In fact, when I started it, I think it blew it out because it shot up to "H" for about 3 seconds, then dropped and doesn't read anymore. My question now is, why is that happening and what can I do to fix it?

On a more positive note, I drove the jeep for the first time since early April...drives better than I remember. All the lights are working.... just put on the fender flares, aluminum rockers, and even put the "LAREDO" decal on the glove box lid. Getting there!!!
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post #10 of 16 Old 07-12-2020, 05:33 PM
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did you change both the fuel and temp gauges?

Sometimes the don't mix


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post #11 of 16 Old 07-12-2020, 05:47 PM Thread Starter
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No actually. just the fuel gauge.......
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post #12 of 16 Old 07-12-2020, 06:05 PM
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Nice job on the Jeep looks great.

Not to be a jerk but take those wire nuts out and replace with a proper connectors.
Wire nuts will vibrate off in a vehicle and cause a short.


Whats over that next ridge?
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post #13 of 16 Old 07-12-2020, 06:48 PM
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Quote:
Originally Posted by royslaredo View Post
No actually. just the fuel gauge.......
Depending upon what type, You could be sending unregulated voltage to the temp gauge and that might of what caused it to go full scale.

There are other things but lets work on one problem at a time.

Need to get a matching temp gauge.

Do you remember what one you bought?


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post #14 of 16 Old 07-12-2020, 07:02 PM Thread Starter
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Originally Posted by 4Low2G0 View Post
Nice job on the Jeep looks great.

Not to be a jerk but take those wire nuts out and replace with a proper connectors.
Wire nuts will vibrate off in a vehicle and cause a short.

Hi,
No worries, I already replaced them. Thanks for the bump on how the jeep looks. Going on a 3 year build...here's the thread I started but never finished because..I was working on the jeep...
https://www.jeepforum.com/forum/f22/...oenix-4380547/

WHen I have nothing else to do on the jeep maybe I can finish the thread.....
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post #15 of 16 Old 07-16-2020, 06:56 PM Thread Starter
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Ok John, to be sure, I ordered and replaced both the temp and fuel gauge with omix-ada ones. I put them in tight and think they are seated properly. I have to say the new ones are even cheaper then the ones I bought several years ago...there's no round metal housing, for example, just has all the insides exposed... .. I put them into the speedometer, installed that, reconnected all the wires and bulbs and basically put it all back together as it should be, then started the engine. Here's what happened: the temp gauge needle dropped (to the left) and went out of sight. The fuel gauge did register but much lower than what it was before. The gauge I had on there before was reading just over 1/2 tank, and this one reads just barely over empty and seemed to move much slower. After running for perhaps 30 seconds, the 15 amp ign lps fuse blew, and the temp needle jumped back to the "C" setting... sigh....any suggestions?
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