Can someone with a Hughes Autoformertell me if it is normal to measure around 10 ohms of resistance between the hot and neutral prongs of the plug? I was expecting infinite resistance, so hoping to see if this is normal or not.Initially I thought it was the plug, because there was some corrosion and melting on on the hot terminal, but I cut off the plug and the bare wire measures the same.Thanks

That implies a 12A draw. What is the actual amp draw?

A DC resistance of 10 ohms sounds rather believable. Offhand I would expect a lower resistance, based on a rather simple understanding of how it may be set up, but I don't have any specific values or very detailed design info to be be very certain. The DC resistance of transformer coils is by design quite low since any resistance there simply results in inefficiency and heating. The primary (and also the secondary, or at least a portion of it, since it's the same winding in an autotransformer) would presumably be connected more or less directly to the plug.Signs of excessive heat at the plug prong is due to a poor connection right in that area, either where the wire attached to it, or between the prong and the spring fingers in the socket it was plugged into, or between the wire and the socket. Replacing the plug is a very good idea if you find it in that condition.

How long has it been since the plug you had heating problems was disconnected.If a plug is left for a long time corrosion will build up and cause a high resistance connection.I have a Hughes Autoformer that was permanently mounted in my trailer. I had used the plug connectors and they were never disconnected as I always used the Autoformer. After about 5 years I discovered the same heating and melting problem you described.I removed the plugs and made a permanent connection with wire crimps which I soldered after crimping. This required opening the case of the Autoformer which I did not mind as the Autoformer was way out of warranty.If you do not want to wire direct I would recommend disconnecting and reconnecting the plugs after each trip. This will break the corrosion that forms.

Autoformer is not an isolation transformer but rather one big coil with several tap points to get the different voltages. How would it work with an open circuit? There is no power switch.If this is about the plug melting, this is fairly common during high usage as many pedestal connectors are worn, pitted, dirty and corroded causing a poor connection and some heat.

I would guess it is normal without breaking out the meter. A transformer tends to be right close to a short circuit at DC levels. But at AC it is a much higher Impedeance This is true of all inductive devices.

Autoformer issue | Good Sam Community

wa8yxm
Explorer III
Jul 21, 2020
Cummins12V98 wrote:
If you want a FACTUAL answer simply contact AutoFormer!

THeir response was already up -thread

For the person who ask. I'm not good at drawing with the computer and do not have the kind of tablet that would let me draw it.

So I will describe

I needed to, as I recall buck about 10 volts
So it was a 10 volt transformer.. Primary connected to incoming power. I "Broke" one lead of the device's power transformer (A tube tester by the way) and put the secondary (10 volt) winding of the buck transformer in such a way that it was out of phase so it "Bucked" the incoming power.. Worked great Was able to dial the needel to the calibration mark every time.

Simple really.
time2roll
Nomad
Jul 21, 2020
I don't know any company that is going to supply a schematic except to an authorized repair facility.
MEXICOWANDERER
Explorer
Jul 21, 2020
You'll get a better response asking a battery company about their plates.

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