Lose of 12 volts to Propane Gas Detector.

[Zebrafive]

Hello to all, I am new to the forum and need help solving an electrical problem. I have a 5th wheel Prowler 22.
Several months ago my Propane Detector went into an alarm, and I could smell gas. I called a service man who said he "Tightened" up some connection and also that my Detector needed to be replaced. (Worked fine before he got there) I fould that he had removed the detector and just stuffed the exposed wire back into the panel wall (I believe that may have momentarily shorted) . Now when I measure the voltage, I have 12.57 VDC, however, when I connect a load...IE A new detector, my fingers.... the voltage drops down to about 3 VDC.
So I guess my question is whether or not the 12 VDC comes right from the 12 volt battery bar, or is there some type of buffer between the two that might be defective.
Thank you for any help you can provide....

Jim

 

[JohnDar]

The gas detector is normally wired direct to a 12V source so it’s always active. Because it activates does not stop it from working again once they’ve been cleared with fresh air. You can actually test them with the gas (no flame) from a butane lighter.

Check the manufactured date on the back. Typical life on them is 7 years. Replacing them is simple.


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[Zebrafive]

Thank you, John.
The detector is brand new and runs fine on a 12 VDC power supply I have in my workshop. The problem is with the 12 VDC supply in the camper. Anytime the detector is connected the 12 volts drop to around 3 VDC...However, all other 12 VDC items work and the battery bar measure 12 VDC from all breakers. There must be some other component between the battery and the 12 VDC wiring for the detector.

Thanks again for the reply.

Jim

 

[wdk450]

The dropping of 12VDC to 3 volts DC under load conditions is typical for blown indicator fuse panel (LED fuse blown indicators) fuse for that circuit. This is a little odd since by code, the propane detector alarm is supposed to be wired WITHOUT an external fuse, only being protected by an internal fuse within the detector for best power loss propane detection safety. With loss of 12 VDC supply, the alarm should BEEP to notify you of this condition until the alarm's internal backup battery runs out.

See if you have a 12 VDC fusepanel, connect a load to the circuit where the alarm normally connects, and see if an indicator LED lights on the 12 VDC fusepanel. Alternately, you could use an ohmmeter to individually check EVERY fuse on the fusepanel, and replacing any blown fuse.

BTW, you read 12 VDC on the end wire open circuit, due to the very high input impedance on the DVM causing a miniscule measuring current, supplied by the forward current of the unlit indicator LED on the fusepanel with the open circuit. When you apply a normal load the current path to the blown fuse does not bypass current around the LED as it normally does (the fuse is connected in parallel across the indicator LED) the LED conducts and lights, limiting the voltage across the LED to 3 volts as a normally connected semiconductor diode does.

 

[Zebrafive]

Thank you so much for all that info.

There is a fuse panel at the base of the Couch/bed in the living room. I was under the impression that these were all 120 VAC fuses.
I could not find a DC fuse panel in the camper, unless it's located in an area I am not aware off.

The LED indicator/fuse theory makes perfect sense. I will look into that. (There is 13.2 VDC at the battery so the 12.5 I am seeing on the meter shows the .7 diode drop.)

Thanks again!

Jim

 

[Bogie]

There is a fuse panel at the base of the Couch/bed in the living room. I was under the impression that these were all 120 VAC fuses.
I could not find a DC fuse panel in the camper, unless it's located in an area I am not aware off.

From pictures of a Prowler 22 5th wheel, the fuse panel you reference houses both breakers (AC) on the left side and fuses (DC) on the right side.
This is pretty typical arrangement.

 

[Zebrafive]

Below is a pic of the fuse panel. Are the DC fuses the row of blue automotive fuses at far right? It would make sense as I see a couple of white with orange tracer wires and thats the color of the detector wiring (Wht/Orn + and soild white -)

Thank you for the guidance.

Jim

 

[Bogie]

Below is a pic of the fuse panel. Are the DC fuses the row of blue automotive fuses at far right? It would make sense as I see a couple of white with orange tracer wires and thats the color of the detector wiring (Wht/Orn + and soild white -)

Yes. That's right. Hard to say about the exact wiring. You will have to investigate that circuit individually.

Also, though you didn't ask....FYI.... the unit on the bottom is the converter for the 12 volts and charging the battery.

 

[Zebrafive]

Your help, (Everyone’s) has been incredible. Quick, precise and friendly. (Campers Rock!)

Raining here today. (Rhode Island) but I will scope out and test the fuses and get back to you on what I find. (With all the info the forum has provided, I am sure that is the solution…..a bad fuse.)
I have a feeling its that little 1 AMP fuse at the very bottom….but I will check them all.

Thanks for verifying that expensive looking thing under the fuse panel. I thought that was the converter based on the cooling fins….looks like the one I have for my car. (But a reverse 12 DC to 120 AC)

Thanks again to all.

Talk soon.

Jim

 

[Zebrafive]

The rain let up so I went to investigate the fuse issue and below is the culprit.
Measures about 1.3 MEG Ohms. Just enough to allow a VOM reading for voltage but too much to run a load of any significance.

Thanks so much for all your great help!!!!

Jim

 

[wdk450]

With these automotive type 12 vdc fuses, besides measuring them with an ohmmeter, and looking for the small LED blown fuse indicator (from your pic I can't exactly see the LEDS, but I think I see the symbol for them printed in white ink next to the upper right of each fuse), you can usually look between the 2 terminal blades and SEE the blown metal U shaped fuse element. Again, to make the blown fuse indicator LED light there has to be voltage on the circuit, and a complete current path to ground (through a switched ON load, or a short to ground). Pulling out the fuse will simulate a blown fuse to test the indicator LED.

What part of Rhode Island are you in? Back in the early 70's I spent a lot of weekends in Cranston at my sister's 100+ year old factory row house on Maple St. at Park Ave., as I was in the Navy in the Norfolk area over a few years, and the rest of my family was in California.

 

[Zebrafive]

The rain let up so I went to investigate the fuse issue and below is the culprit.
Measures about 1.3 MEG Ohms. Just enough to allow a VOM reading for voltage but too much to run a load of any significance.

Thanks so much for all your great help!!!!

Jim

View attachment 68639

With these automotive type 12 vdc fuses, besides measuring them with an ohmmeter, and looking for the small LED blown fuse indicator (from your pic I can't exactly see the LEDS, but I think I see the symbol for them printed in white ink next to the upper right of each fuse), you can usually look between the 2 terminal blades and SEE the blown metal U shaped fuse element. Again, to make the blown fuse indicator LED light there has to be voltage on the circuit, and a complete current path to ground (through a switched ON load, or a short to ground). Pulling out the fuse will simulate a blown fuse to test the indicator LED.

What part of Rhode Island are you in? Back in the early 70's I spent a lot of weekends in Cranston at my sister's 100+ year old factory row house on Maple St. at Park Ave., as I was in the Navy in the Norfolk area over a few years, and the rest of my family was in California.

Hi Bill, I am In Warwick. Right next door to Cranston. My wife is from Cranston.
There are still a few row house areas left today, but most have been torn down as well as the factories they once served.
It's not the Rhode Island I grew up with......I guess no place is if you're over 60.