Community Forums

adamdan · 09-15-2015, 06:32 AM

hi, I have a 1971 ford E=300 motorhome- I cannot find an ac/dc converter, is it possible with this old of an rv that it does not have one and it is just 110v direct? please advise

John USA · 09-15-2015, 06:47 AM

What kind of interior lighting does it have?

adamdan · 09-16-2015, 09:26 AM

the lights are 12v but im wondering if they run straight off of my back-up battery- and then is it possible that the outlets in the rv are 110v direct.
is this possible

John USA · 09-16-2015, 11:23 PM

Anything is possible.

Disconnect your battery, and see if your 12v lights work or not.

If they still come on, then your converter is really hidden!

If they don't come on, then your theory is probably right.

guardrail53 · 09-16-2015, 11:56 PM

Follow your elect. cord into the MH, and it will lead you to your converter! Look under the fridge, in the bottom of the cabinets, under a access panel? Your cord will lead you where to look! Also look in the back of the MH, but they put the converters in crazy places sometimes! Have someone unplug and replug the cord in while you are in the MH, listening for it to kick on. Also look at the lights after plugging it in, they should get brighter if your converter is working! It could just have tripped breakers, which are on the back side of most, some behind a access panel! Good Luck! Rail!

KSagal · 09-18-2015, 08:07 PM

One other test you can do, but you must be careful.

Turn off all lights. Unplug the land line. Disconnect the house battery. (Engine off of course)

Be sure all battery lines are safe and separate, no touching anything.

Plug in the land line.

Measure the voltage across the two house battery cables.

If there is an inverter, you will have voltage on those cables, no question. If you have no voltage, you may be right, there is no inverter.

I would have to presume that if there is no inverter, then the house battery gets charged from the engine when running. This may be another way to test what is going on...

Libero · 09-18-2015, 08:15 PM

KSagal, doubt there is an inverter, but if you are talking about a converter - having problems with the logic. Most chargers have a safety relay, no battery voltage then no voltage present at the disconnected leads. But perhaps a 71 model does not have that feature - in any case NO INVERTER most likely,

KSagal · 09-18-2015, 08:51 PM

I may be using the wrong term. An inverter makes AC power from DC power.

I am not so sure what makes DC power from AC. I call them all inverters, but perhaps it is a converter.

Bottom line is that something, somewhere has to charge that house battery. Even in 71, I would not guess that the battery never gets charged. (Again, it may be charged from the engine alternator, but I would not guess that is the only way)

In my MH, the house battery is charged from a converter that is powered by 120v AC, and delivers about 14 volts DC to the house battery.

Now, if my formula above is followed, and a multi meter is set to measure the DC voltage between the disconnected positive and negative leads, and there is a charging circuit (from the converter) it will read somewhere north of 12v DC.

If there is no charging circuit, it will read 0v DC.

Libero · 09-19-2015, 07:57 PM

KSAHAL - Suggest you try what you propose on your rig. e.g. disconnect the house battery/batteries and then apply 120vac to the rig and measure the voltage at the disconnected battery cables. It may read 0V DC because the safety relay could have shut the charging circuit off. Don't recall if they did that in 71 but many, perhaps most, shut the charging circuit down if low or no voltage connected. I had a TT in 71 but it did have a converter/charger but never had any problems.

KSagal · 09-19-2015, 08:25 PM

Quote:

Originally Posted by Libero

KSAHAL - Suggest you try what you propose on your rig. e.g. disconnect the house battery/batteries and then apply 120vac to the rig and measure the voltage at the disconnected battery cables. It may read 0V DC because the safety relay could have shut the charging circuit off. Don't recall if they did that in 71 but many, perhaps most, shut the charging circuit down if low or no voltage connected. I had a TT in 71 but it did have a converter/charger but never had any problems.

You may be right. I was speaking from a perspective of theory, not personal experience.

Perhaps a better test would be a simpler one...

1. Unplug the shore power.
2. turn on a number of 12 volt lamps or devices
3. Measure the voltage at the house battery. IF the battery was good, and relatively charged, it should be in the neighborhood of 12 volts with a load.
4. Plug in the shore power line.
5. Again measure the voltage at the house battery. If there is no converter, the voltage should remain essentially the same.
If there is a converter, the voltage with the same load should be higher, because it is also charging.

What say you Libero? Would that test be okay?

I was not giving advice I would not take myself, but I know I have a converter that charges my house batteries. I just am not that familiar with these things, but I am learning...

By the way, my MH has a power distribution system that uses shore power to do many things, including charge the house batteries, but it does not charge the truck batteries. That is one thing I will be adding, as well as an inverter.

This time I am sure I mean inverter, because it's function is run off the 12 volt DC system (house batteries or alternator) and produce 120 volts AC.

Libero · 09-20-2015, 02:42 AM

KSsgal - Yes, your test will validate if a converter/charger is present and working. Good place to start. But this will not determine if one is there and not working. A converter/charger is likely not far from the batteries if it exists. In 71 the technology was much less advanced and this would not be a very small device. But aftermarket products could have been installed. If there is no change in voltage at the battery with the AC connected, as you proposed, I would trace the wires, visually at first and then using my signal tracer for hidden wire routing. I would draw a schematic of the entire coach showing wire routing - have done this with every RV I have owned since the 60's. Hope the OP reports back with his findings.

Piker · 09-20-2015, 03:11 AM

WARNING:

For anyone who wonders... you can't just grab a cheap $50/$100 modified sine wave inverter and plug it into your coach's electrical system. The modified sine inverters work much differently than regular "house" electricity. Instead of having a single hot line with 120v, a single neutral line, and a ground... they actually have two 60v hot wires (black and white) and a ground. The hot wires are out of phase with each other and cycle @ 60hz to "simulate" 120v. Not sure, but it's kind of like the difference between 120 vs. 240. Mind you... I'm not an electrician... but a little experimenting with a voltage meter tells the tale. Always do your own research...

At any rate, if you try to hook the neutral from your inverter... which is actually HOT... to the neutral in on your coach's service panel... which is bonded to the ground... you will instantly fry the inverter.

You will either need a true sine wave inverter, or use a couple smaller inverters to use as "point of service" type installations. I wired a modified sine inverter under the dash in our rv with a power strip just for charging phones and electronics. It also works to power the TV when we're dry camping.

I would think adamdan's RV has a converter somewhere... it probably just doesn't work? Not sure though as it's a pretty vintage unit. A new "smart" converter by progressive dynamics can be had for around $150.

-cheers