Scratching head over lighter plug wiring (Sirocco Fan)

Submitted: Saturday, Sep 30, 2023 at 16:07

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Member - silkwood

I'm just installing a Sirocco 12v fan in the RTT. I've wired it to a cigarette (socket) plug so I can also mount it on the side of my canopy if required.

I have wired it to the common inlet from my house batteries, this inlet runs the led light (works fine) and a 12v blanket (works fine). All wiring and fusing is adequate. I have the female socket wired via an anderson connector, same as the wiring for the blanket. The wiring to the socket connector shows 12.75v at the pins (checked the wiring to the light and blanket, same...). However as soon as I plug in the plug from the fan it shows 1.95v. Tried a usb outlet (which glows blue when power available) and it shows 4.2v!?

Both the fan and the USB outlet work fine from the other outlets attached to the same system, just not this one in the RTT. So I purchased a second outlet... same result!.

With the wiring oversized for the use (fan draws very little) and all fuses intact (and working on other outlets) I cannot figure what is going on.

Any suggestions?

Cheers,

Mark

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Reply By: Allan B (Sunshine Coast) - Saturday, Sep 30, 2023 at 18:34

Saturday, Sep 30, 2023 at 18:34

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Mark, it sounds very much as though you have a high resistance somewhere along the line, probably at a junction point. You get 12.75v at the socket with no load but when you ap[ply a load the voyage drops.
Try plugging the fan in and then use your voltmeter to read from the terminals at the socket and work back along the cable, measuring at each accessible junction. This should indicate the point at which you are losing the voltage.

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Allan

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Follow Up By: Member - silkwood - Saturday, Sep 30, 2023 at 20:33

Saturday, Sep 30, 2023 at 20:33

I'll check that out next.

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Mark

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Follow Up By: IvanTheTerrible - Saturday, Sep 30, 2023 at 21:47

Saturday, Sep 30, 2023 at 21:47

Or the cable is to small or the run to long. With that voltage drop that big a bad joint would be very hot

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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 30, 2023 at 22:16

Saturday, Sep 30, 2023 at 22:16

Well Ivan, using Mark's supplied values, I have calculated that the wattage being dissipated is about 2W so that would not be a great deal of heat, although certainly warm to the touch.

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Allan

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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 30, 2023 at 22:23

Saturday, Sep 30, 2023 at 22:23

Mark, I should perhaps have pointed out that the loss may be in the negative return path so you need to check that also.

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Allan

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Follow Up By: Member - silkwood - Sunday, Oct 01, 2023 at 16:58

Sunday, Oct 01, 2023 at 16:58

Turns out I never learn lessons! The fault was in an Anderson 2-to-1 connector I purchased at a camping show a couple of years ago. I bought two as they were cheaper than making my own up.

The part about not learning was that the first one was wired backwards, had me wondering why my 12v oven wasn't working. This one had a faulty crimp, hardly connecting at all to the second Anderson plug.

Beware of cheap electrical gear at camping shows!

Thanks for the assistance, fan working perfectly now.

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Mark

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