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Discussion Starter #1
The setup worked a couple years ago. I tested the motor with a car battery and it works. I also put the meter on the outputs of the computer power supply and I get 5 volts on the red and 12 on the yellow. When I connect the motor to the power supply the motor doesn't turn at all, I measured with the meter while all is connected and I get a very low reading .1 - .2 - Can't figure this out, any advice? Thanks.
 

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Don't most of the computer power supplies need a resistor to turn them "on"?
Are you sure you aren't shorting the motor out with incorrect connections?
What voltage are you trying to use. That will have an effect on the amperage rating of the power supply. Is it possible that the motor is not connected properly? These are the things that come to mind right off the bat. What is the wattage of the power supply? If this has been in storage for awhile I would check all connections to make sure they are tight and clean, no corrosion, there are many other possibilities but these are probably the most common. Good luck. The low readings almost sound like a direct short to ground.
 

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If memory serves, connecting the green wire to ground will turn a supply on. On most supplies, there is an always-on supply at 5v so you might see a little voltage on the other wires as well.

Does the supply have fan that's running?
 

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Do you have a speed control on the set-up? If so try to take that out and direct connect the motor and see if it runs.

Is your ground wire connected to the ground at the motor plug? I have found that if I take out a screw on the motor case and hook the ground directly to the case instead of the plug wire i get better results.
 

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Test to see if there is a voltage sag or drop. Make your connections, but include two sections of bare wire, just enough to get a multimeter's probes on them. If you get a non-load voltage of 12 VDC, but under load the voltage drops significantly, then the power supply is dying. For whatever reason, it cannot handle the current draw from the wiper motor.

Something to consider:

"At any rate an average wiper draws 5 amps, rising to 10 to 12 amps under heavy/stall load. Supposing the motor efficiency is 60% then the total power maxes out around 4 x 10 x 12 watts = 480 watts input and 0.6 x 480 watts output power ."

So if your CPU power supply is rated for 350 watts (which is typical) and your wiper motor is drawing 480 watts, you're cooking it to death.
 

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Discussion Starter #6
If memory serves, connecting the green wire to ground will turn a supply on. On most supplies, there is an always-on supply at 5v so you might see a little voltage on the other wires as well.

Does the supply have fan that's running?
The unit has a on/off switch and the green/black is bridged, fan is running. As i said before, this setup was working a couple years ago and its been in storage since. The connection is pretty simple, 2 wires out of the motor, black to common and one of the 2 wires, yellow for 12v or red for 5v to the other lead. No speed controllers, the 5v was the perfect speed for my application. I think Bryan316 is right, the power supply must be frying under load.
 

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If it worked before and nothing has changed, safe to say it's the power supply that has gone south. Might be worth a quick look inside the PS, see if any of the can capacitors have bulged on top. They only last so long and are easily replaced if you can solder.
 

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Discussion Starter #12
I found another power supply in the garage, hooked it up and the motor started spinning. The old unit was on the way out. The witch will be stirring the cauldron this Halloween. Thanks for all the replies.
 

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I am confused...Are you connecting the motor to both 5vdc & 12vdc at the same time? (1 lead to the 12vdc, and the other to 5vdc.)
 

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I am confused...Are you connecting the motor to both 5vdc & 12vdc at the same time? (1 lead to the 12vdc, and the other to 5vdc.)
No, he's not doing that. Any DC load needs a positive and a negative connection to function. So you would either use the 12v and a negative or the 5v and a negative.
 

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No, he's not doing that. Any DC load needs a positive and a negative connection to function. So you would either use the 12v and a negative or the 5v and a negative.
Correct, common (black) and I'm using the red wire (5 volts) which gives me the slower speed I need. If you want the motor to spin counter clockwise just reverse the wire connection.
 

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Yep, this brings back a horrible memory... I used to use a computer power supply and it ran my haunt for a couple of years then it died just hours before showtime for Halloween 2016. Your experience just further confirms the trouble with using them. I have decided not to use them. Even though these Power Supplies are used only a few hours every year compared to the years of use in the computer... I guess they breakdown due to their age and perhaps the +12V supply may not withstand heavy and/or inductive and/or spiky loads. What I've done instead was to purchase a beefy 12V power supply to run my haunt and I use some PTC fuses so I can isolate individual circuits against shorts. Another solution is to have several smaller 12V supplies (but appropriately sized) for each prop / light / etc and I have extra on hand for spares. Either way, I've standardized on the power connectors (voltage and polarity) so I can swap them out quickly if needed. So far I've been lucky.
 

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Yep, this brings back a horrible memory... I used to use a computer power supply and it ran my haunt for a couple of years then it died just hours before showtime for Halloween 2016. Your experience just further confirms the trouble with using them. I have decided not to use them. Even though these Power Supplies are used only a few hours every year compared to the years of use in the computer... I guess they breakdown due to their age and perhaps the +12V supply may not withstand heavy and/or inductive and/or spiky loads. What I've done instead was to purchase a beefy 12V power supply to run my haunt and I use some PTC fuses so I can isolate individual circuits against shorts. Another solution is to have several smaller 12V supplies (but appropriately sized) for each prop / light / etc and I have extra on hand for spares. Either way, I've standardized on the power connectors (voltage and polarity) so I can swap them out quickly if needed. So far I've been lucky.
Since this incident, I found another computer power supply and other smaller wall plug-in type units. I don't run the prop continuously, it's connected to a motion sensor under the overhang by my front door, this might cause the spike loads you are talking about. Also the old unit had been stored for 3 years in a musty area of the basement, the casing was a little rusty, the electronics may have been affected by the moisture. But you're probably right about the application possibly putting too much strain on the unit, we'll see.
 

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What I've done instead was to purchase a beefy 12V power supply to run my haunt and I use some PTC fuses so I can isolate individual circuits against shorts. Another solution is to have several smaller 12V supplies (but appropriately sized) for each prop / light / etc and I have extra on hand for spares. Either way, I've standardized on the power connectors (voltage and polarity) so I can swap them out quickly if needed. So far I've been lucky.
I shortened the quote , but this is what I've suggested to many others and do myself. Currently i have very little in the way of props but i do have a power supply set up that is plenty capable of supplying 5 and 12 volts . Separate power supplies but set up on i1 board along with a 16 relay board that will be going into a regular cabinet along with the controllers and possibly the pneumatic valves.The power supplies are very reasonably priced and work very well. We use them in the plant I work at.
Here's a link to the ones I use http://www.mpja.com/Hengfu-Switching-Power-Supplies/departments/465/
 

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From the sounds of it... I'd worry that the Power Supply might give out on you without warning, like it did with me. And rust / moisture and electronics don't mix... well... not for very long and then there you are. It would be sad if your prop gave out on you Halloween night.
 

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I've replaced many power supplies in computers over the years. They have a lot of hours on them by the time we get them so it isn't unusual for them to go bad. I found that it was always a good idea to at least turn the computer on before pulling one for haunt use.
 
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