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Tachometer problem - not working

I recently purchased a 2002 IS300 Sport Cross. Everything was working on the car until this morning. The tachometer, MPG not working and the oil level light, and rear bulb indicator were on. What changed. Well here is what I found out. I had plugged in a USB phone charger to my cigarette lighter to charge my phone and started having the issues. Take out the USB phone charger and all issues go away. Weird but I can replicate the issue.

How does the cigar lighter have anything to do with the tachometer or any of these other dash issues?
 

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i know it’s been a few years since this thread, but i have searched everywhere and not been able to find a fix or resolution to this issue. i am having the same issues. my tachometer and mpg gauge stop working and at the same time the oil light and tail light indicator come on. this issue had gone away temporarily and then last night my horn went off randomly and i had to disconnect the battery to make it stop. now the tachometer issue is back and my security light is solid red all the time. even while driving.
please help..
 

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Do they share a ground connection?

Also sounds like your alternator or battery could be going bad; just by the sounds of it, I would test it before you're sitting on the side of the road. Random things in your electrical system do weird things when they go bad. Does the little battery light also come on? What is the voltage on the battery when the car is off and when the car is idling?
 

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the battery is fine. new within the last year. i have tried pretty much everything that has been suggested in this thread prior to my post. there is another thread that discusses part of my issues.. with a few posts who also had all of the same things going on as me and no resolution there either. i swapped the horn relay. replaced the horn fuse and the 10a guage fuse as well. my oils is good, my tail lights/brake lights all work fine. and i just disconnected both battery terminals to reset the ecu to see if that would help, all to no avail.
 

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When you recommect the battery does the horn continuously sound are have a rhythm like goes every other second for half a second long or something?

What is the voltage coming from the alternator at idle?
 

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i took out the horn fuse to keep it from sounding. when i put it back in today, it didn’t sound at all. but the other tachometer issues are still there. it seems to happen when the car is exposed to moisture. i can’t find any water anywhere. but the issues always happen after rain or snow. i don’t know how to measure anything on the alternator.
 

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I know this is an old thread that keeps coming back. Well I have the issue. But I am reading here on possible solutions. Mines is an 02 Manual. I do have 2 things plugged in. DashCam and my Iphone charger. Ill disconnect both next time I see it.
Happens for me mostly when my car sits in the sun. Every time I head to work at our new office with no shade, I see it on the return trip home. Its off and on. Same thing, tail light indicator and low oil and the tach drops to zero. Then it comes back and everything is fine but will do it again over and over til I get home. Strange, like Doctor.
 

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I know this is an old thread that keeps coming back. Well I have the issue. But I am reading here on possible solutions. Mines is an 02 Manual. I do have 2 things plugged in. DashCam and my Iphone charger. Ill disconnect both next time I see it.
Happens for me mostly when my car sits in the sun. Every time I head to work at our new office with no shade, I see it on the return trip home. Its off and on. Same thing, tail light indicator and low oil and the tach drops to zero. Then it comes back and everything is fine but will do it again over and over til I get home. Strange, like Doctor.
Bad connection. I would look at the ignition switch contacts. Or the cluster connections.
 
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