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I could really use some help. I recently purchased these items:

12V DC 2.5A Blower
12V 6A 72W Power Supply

I hooked the positive wire of the blower to the positive terminal on the power supply. I then connected the negative wire of the blower to the negative terminal on the power supply. When I plugged the power supply in, the blower twitched, stopped, twitched, stopped, etc... I unplugged the power supply. I tried reversing the wires. I Googled & Googled quite a bit and everyone is saying just what I assumed ... just get an AC/DC power supply that provides more amps than what the blower says it draws which is exactly what I think I did. This just doesn't work.

Am I missing something? I suppose it's possible that the blower draws significantly more amps on startup than listed.

Looks like should work

Hey, Nails. Your supply is adequate. Should even be for start up inrush current, but some motors just suck a lot of current on startup.

I deal with this sort of power supply all the time. Make sure the AC plug into the power supply is FIRMLY inserted.

If that doesn't do it, connect the blower to a sizable battery, like a 12-volt car battery, to see if it works and
narrow it down to which is bad. Supply or blower.

What fizzix said - your purchase decisions aren’t the problem, just need to troubleshoot to find where the problem is

Thanks guys! In all my Google searching and reading questions/answers and reviews, I came across another guy who had a similar condition. He just left a bad review for the blower.

I'll try what you recommended. I have a tester, but it doesn't appear to read amps. I really wanted to get a good reading on the power supply.

Test the power supply for volts.

I just did and it reads 12V DC.

Then the power supply is ok, so the problem is the fan. You could try powering up the fan and starting it spinning with something other than your finger, but even if that does get it going, it's still an unreliable POS.

I may try cycling it on & off many times with a 12V battery. Maybe that will break it in or something.

If that doesnt work then I'm returning it all.

Sometimes a switch mode power supply will not start with a load attached, usually if the starting current of the load is high. Try putting a switch between the blower and the supply. Turn the supply on first then the blower. You might find this works where a direct connection does not.

I connected it to the battery in my truck and it kicks on perfectly. I cycled it on & off MANY times and no issues at all.

When I plug the power supply in it takes a few seconds, a red light illuminates, only then does the blower twitch for a second, the light goes out, a second or two off then it twitches again with the light and the cycle repeats.

zed255 wrote:Sometimes a switch mode power supply will not start with a load attached, usually if the starting current of the load is high. Try putting a switch between the blower and the supply. Turn the supply on first then the blower. You might find this works where a direct connection does not.

I just tried what you recommended. I plugged the power supply in, after a couple seconds the light illuminates, I waited several seconds then plugged the blower in. It twitched, the blower & light turned off and the cycle continued to repeat.

I think it's got to be the power supply.

My intention is to connect the power supply to a controller which turns the blower on and off as needed automatically. Installing a manual switch would not work for me.

What is the blower for

The blower I bought is for ventilating the bilge of a boat. It's a 12-volt DC inline blower. The product states its 2.5A DC. I bought a power supply which is 6A DC. it should work.

NineInchNails wrote:I just tried what you recommended. I plugged the power supply in, after a couple seconds the light illuminates, I waited several seconds then plugged the blower in. It twitched, the blower & light turned off and the cycle continued to repeat.

I think it's got to be the power supply.

My intention is to connect the power supply to a controller which turns the blower on and off as needed automatically. Installing a manual switch would not work for me.

I agree that it is the power supply. If you can check the volts while starting the fan, my guess is that you will find that the power supply is cutting out.

BTW, you should be able to use the same controller to switch either the AC to the power supply, or to switch the 12V DC to the fan.

That's likely a switch mode power supply and doesn't have a linear output that is controllable.

Switch mode supplies operate over a wide range of AC input (our store-bought ones like this are 220vac down to 100vac, like yours) WITHOUT fluctuating the DC output.
They are engineered to maintain solid 12vdc over varying AC input.
Your controller just likely will starve the supply and it'll go from a locked in 12vdc to immediate Ø volts.

Switch mode supplies are not like the old transformer to rectifier DC supplies of old.

NineInchNails wrote:I connected it to the battery in my truck and it kicks on perfectly. I cycled it on & off MANY times and no issues at all.

When I plug the power supply in it takes a few seconds, a red light illuminates, only then does the blower twitch for a second, the light goes out, a second or two off then it twitches again with the light and the cycle repeats.

Sounds like your power supply is bad or doesn't like the motors inductive load
A 10 micro-farad or bigger capacitor in parallel with the motor might help

I'm going to return that power supply. I'm thinking about getting this one:

Schumacher PC-6 120AC to 6A 12V DC Power Converter

I assume this power supply is a different technology and hopefully has enough power to run the blower. I'm still shopping around, but this one quickly caught my eye and has great reviews.

Item Weight 15 pounds
There's a transformer in this one

The Schumacher will still not work because it is only providing 6A, the same an your other one..

What you need is a 12v 15 - 20A power supply, similar to the 6A you already have, but of the 15-20A size..

Reason is that your 6A does not have enough amps at the start to make the fan turn.. experience the same situation with an electric window opener, which was rated at 4A, but it took a 20A power supply to make it work, that why it worked on your 12V car battery, which has over 200A available..

Mars

Well that sucks. I'll keep my fingers crossed hoping it works. If it doesn't work I'll return it. I found a 20A one for $17.

NineInchNails wrote:Well that sucks. I'll keep my fingers crossed hoping it works. If it doesn't work I'll return it. I found a 20A one for $17.

I'll bet a jug of my finest, that the old school transformer power supply will spin the motor

shadylane wrote:Item Weight 15 pounds
There's a transformer in this one

I'm with you Shady .
If it is indeed a Basic Transformer , rectifier and filter Cap setup , it will have no problems starting a 2 amp motor .
Question is whether it has a regulator circuit or not . If it has then you could run into over current trip issues again .
A regulator will maintain exactly 12 volts regardless of mains supply variations or load requirements ( so long as the maximum current isn't drawn ) It is the preferred power supply for sensitive electronic equipment .
If there is no regulator then the Nominal output voltage can be anywhere from 11.5- 16 V depending on load .....this is not a problem for things like motors .

Agree with previous comments about switch mode power supplies not being able to supply start current . I tried running a windscreen wiper motor off an old AT power supply once , it would shut down instantly even though it was rated for 3x the current the motor drew when running .

NineInchNails wrote:Well that sucks. I'll keep my fingers crossed hoping it works. If it doesn't work I'll return it. I found a 20A one for $17.

Well done feel bad.. I spend two months on the project and 60 dollars, between a 6A, then a 10A, then a 15A, until I got the 20A, then all was fine.. and every electrician kept telling it should work.. the key word was " should ", as they didn't know themselves and were not honest about it..

The 20A will work, below that, it's iffy..

Mars

StillerBoy wrote:

NineInchNails wrote:Well that sucks. I'll keep my fingers crossed hoping it works. If it doesn't work I'll return it. I found a 20A one for $17.

Well done feel bad.. I spend two months on the project and 60 dollars, between a 6A, then a 10A, then a 15A, until I got the 20A, then all was fine.. and every electrician kept telling it should work.. the key word was " should ", as they didn't know themselves and were not honest about it..

The 20A will work, below that, it's iffy..

Mars

Well at least in my case Amazon Prime makes buying & returning things VERY easy and free return shipping. They even refund you once UPS scans the package instead of waiting until they receive the return. I'm determined to get it right even if it means spending $40 on a proper power supply. I found a 20A for around $18 and another for around $37.

The power supply should arrive today so I'll report back ASAP.

I intend to install a 5A fuse inline as the blower recommends. That should protect against any potential amperage spikes, but I don't know if that will guard against any potential voltage spikes or if that can cause any harm.

You can use an MDL-5 fuse (it's a "slow-blow" 5-amp intended for ramp up and spikes).

NineInchNails wrote:Well at least in my case Amazon Prime makes buying &returning things VERY easy and free return shipping.

Amazon is super, that's why they have become the number retailer, total customer satisfaction, which almost all the other retailer have forgotten about..

Interested to hear back on the 20A power supply.. and I would use a lower amp rated fuse, maybe a 1 or 1.5, but certainly not 5, as it will be way overrated to your blower with is rated at 2.5A..

Mars

StillerBoy wrote:

NineInchNails wrote:Well at least in my case Amazon Prime makes buying &returning things VERY easy and free return shipping.

Amazon is super, that's why they have become the number retailer, total customer satisfaction, which almost all the other retailer have forgotten about..

Interested to hear back on the 20A power supply.. and I would use a lower amp rated fuse, maybe a 1 or 1.5, but certainly not 5, as it will be way overrated to your blower with is rated at 2.5A..

Mars

That's strange. The blower has a sticker on it that specifies using a 5A fuse. Fuses are cheap so it shouldn't hurt if I start small and scale up only if needed. Thanks for that input.

The new power supply works PERFECTLY ! ! !

It kicks the blower on instantly and the blower runs consistently. No initial lag or any irregularities what so ever.

Thanks guys! MUCH appreciated!