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27 Volts!!?? What is going on?


Chad A
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2003 Monaco Signature 42 Triple Crown, 525 ISX. 

 

I appear to have an electrical gremlin somewhere but I need help understanding what is going on. 
 

About a year ago I installed some USB outlets in the dash where the cigarette lighters were. I installed the ones that read the voltage going to them and have a little display on them.

 

I got into the coach this morning for a short run of 45 miles each way on a day trip. As I headed down the interstate the USB chargers started climbing in voltage. Finally settling on 27.2 volts after climbing for about 10 minutes. I get where I am going and shut her off. Sitting here and the volts are at 22.3. My VCM is reading 13.9 while driving and never gets above 14.2. 
 

Any ideas on what could possibly be going on? I don’t want to burn out any electronic pieces in the coach. I also don’t know how where to start looking. I turned the salesman switch off and on and it made no difference. 
 

Thank you in advance. 

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If your voltmeter shows typical battery voltage and the usb outlets show something different, then believe the battery voltage and throw out the cheap usb outlets.

The USB outlets should have a voltage reducer built into them to get 5 volt output.

If you really had 27 volts, you would have fried a whole bunch of things already.

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I have not had a chance to hit anything with the multimeter yet as I left it at home on my workbench in my shop today. The other weird thing is my Sony monitor for the back up camera starts to scramble every time the voltage goes above 15 volts. If it drops below that the picture is clear. Above that it scrambles and will shut off when the reading is over 17 volts. 🤷‍♂️

I have 2 of them and they both read within .1 volt of each other. My Sony monitor will not even turn on now which effects my VCM ability to work correctly. 

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You probably have a defective volt read out on your usb outlet.   Just another thought, do you know for sure that the usb outlet is wired to the chassis batteries, or could they be wired to the house????

I would start with the voltmeter checking at the usb outlet for, input voltage.  Are you only getting the high voltage reading on the usb readout?  If you do have an actual voltage going above 15vdc, as said above, it will start effecting all kinds of equipment.  You definitely have something going on, but need to understand what your actual vdc readings are to share more ideas.   Don't want to send you on a wild goose chase.  Check voltage running and not running, plus at the dash and at the batteries.

 

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The USB outlet with digital read out i had used to go the other way, in that it would drop voltage, when i wired it, i purposely wired it to the coach batteries, often times on a trip it would take usually 45 min before it would start dropping voltage. One particular trip i became so frustrated i skinned the wires enough so as to connect my DVOM, sure enough the read out would drop, however the DVOM stayed  rock solid on the same proper operating voltage as the main battery which was 14.2

Yes it ultimately effected my phone charging when it would do that, so my conclusion was my Fluke DVOM cost over $300. An the USB charger was like $16..  working with automotive electronics over the years i had come to know all circuits have “noise” and that these little gadgets do not have the circuitry to deal with it. My advise is either your getting alot of noise “ more than usuall” that needs attention which could be caused from a failing monitor or its the $20. China made USB charger. Disconnect the charger, drive the coach an see if the screen still wigs out.

My biggest lesson of Electrical noise was when cars would start running poorley or even shut down while driving, the discovery was caused from one or more of the ignition coil on plugs causing noise so much noise it would back feed to the engine computer to scramble the commands, once we determind which coil was the culpret a new coil was installed an problem was resolved…. I dont mind saying it took awhile to sort that problem out!!!

FYI our minds are continually processing input which forces us to act accordingly, when my reader would start dropping voltage down to like 8 volts i would reach over an start my generator knowing it would power the inverter to charge the what appeared to be batteries going dead… What made me challange the USB charger was the generator ALWAYS turned over like normal, which if those batteries did in fact have low voltage i guarantee you it would not have started. Like your self if your system was dealing with abnormal high rate of charge any other electronics woul in fact let the smoke out and lights would be burnt out.

 

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Go buy a cheap meter and start at the batteries. Run the engine while metering. Your comment about voltages going over a certain point and the Sony acts up screams of a voltage regulator issue.

Batteries low on water may be contributing to the issue by not putting enough of a load on the alternator. 

If you see the voltage higher than it should be at the batteries you need to inspect them as suggested and putting a load by turning the inverter on and running the microwave might give you a clue if the voltage comes down a bit with the load. 

Those inexpensive usb chargers are screaming of a problem you do not want to ignore. Your Sony may have paid a price already and hope it is only a fuse.

When voltages go higher or lower than components are designed for they can have runaway currents flow where they should not and let out as much smoke with low voltage as they do with high voltage. 

Again, forget the expensive meter left behind. Borrow or buy another one. It does not have to be Nasa grade 

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So, I checked the voltage at the batteries and all is well. 13.6 volts. Each battery has its water topped off so all is good there as well. 
 

Engine running or not running does not make a difference on batteries or the weird voltage. 
 

What do I check next? I would really like to not tear the dash out again as I don’t know how many more times it can take it before it just falls apart. I can’t believe it has lasted this long with it just being plastic and supporting all that weight. 
 

Thank you for the ideas. 

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You have proven that it is a piece of junk. If you are hesitant to remove the dash (I would be too) then just leave it be. Is there a way to remove the power to it so it won't mess up your Sony monitor screen?

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There is no way to remove them other than to take the dash out again. I put them in when I replaced the dead radio head unit. 
 

So, another question. All I did when I put those in was to take the wiring off of the cigarette lighters and connect it to the usb inserts. Why would that cause my voltage to spike or appear to spike or cause my monitor and VCM to go wonky?

 

I understand the basics of electronics but this one has me baffled. 

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9 hours ago, Chad A said:

There is no way to remove them other than to take the dash out again. I put them in when I replaced the dead radio head unit. 
 

So, another question. All I did when I put those in was to take the wiring off of the cigarette lighters and connect it to the usb inserts. Why would that cause my voltage to spike or appear to spike or cause my monitor and VCM to go wonky?

 

I understand the basics of electronics but this one has me baffled. 

As others have stated, your problem is the USB adapter.  Since you have a basic understanding of electronics, you know that the adapter you installed is taking 12 VDC (nominal) and reducing it to 5 VDC for the USB.  The adapter is obviously junk and the display is not reading accurately.  Furthermore, the electronics that are reducing the 12 VDC to 5 VDC are introducing the interference you see on your display.  I think you’ll also find that this device is causing interference that you can hear on the radio.  Bottom line is get rid of the USB adapter.

Dan D, 2012 Diplomat 43DFT

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