[fritter]

Last Easter I bought a twin cylinder air compressor off Ebay,

The price was great, around $70 with free shipping.
I soon found out that you get what you pay for.

Upon unpacking the box I found one of the plastic air filters broken.
No biggie these things happen and I thought I'd try it out anyway.

Connected the cables to the battery, flicked the switch and....

Nothing! It was dead.

A pleasant email was sent to the Australian seller and they asked for a picture of the problem.
I considered taking a photo of myself standing next to a flat tyre and looking sad as I didn't know how else to show it not working.

Instead I took a photo of the broken filter and explained the problem again.
No response.
Several more emails proved that they had no interest in replacing the compressor.
So I opened it up and took a look inside.

What I found was that the earth wire wasn't connected at all,
and the quality of the soldering of all connections was extremely poor.

After re soldering the earth it worked great. Inflated my 29 inch tyres from 10 to 25 psi in about 40 seconds.

Then the third time I used, it the power switch broke.

Here's what I did to fix it. It's a good reliable compressor now.

The offending compressor.



To open it up. Use an allen key and a small spanner
to remove the the two screws holding the triangular metal plate in place.
It's painful because it's threaded all the way through.

Push the plate up out of the way.
This is what it looked like the first time I opened it.
Disconnected earth.


Take the plastic cap off the green wire and solder the black wire to it.
Make sure you screw the cap back on after soldering as there's no insulation on the +12v at the switch.



I recommend replacing the switch to avoid an almost certain failure later on.
Jaycar part number SK0984 is a direct replacement.
However, it is only rated for 6 amps and as the compressor draws about 36 amps a larger switch would be a better choice.
You just need to increase the size of the slot in the plastic housing to do this.
A hand held nibbling tool would be ideal.

To remove the switch, slide a small flat bladed screwdriver down the vertical sides, and pull the switch towards you..
It's held in place by a couple of plastic tabs.

Mine disintegrated instantly. Check out the soldering!



Pull the wires out and solder them to the new switch.



Ziggy thought it was pretty interesting.



Install the switch by pushing it into the slot until you hear a click.

Reassemble the metal plate, and tighten the screws.

You now have a great (?) air compressor that should be reliable.

Most of these cheap compressors appear to the the same.
I'm guessing they all come from the same Chinese factory.

I hope this helps others who tried to save a buck and were left feeling ripped off.

[dungbeetle]

i bouight a cheapo compressor a couple years ago. it blew up our air mattresses 3 times then the magic smoke came out of it.
i did the same with emails but ended up making a claim thru ebay and got all my money back:D
the refund policy for ebay and paypal are awesome and i have never had trouble getting my money back when i been ripped off.
i have another cheap compressor on its way from china so if this one packs it in ill refer to your notes here.

[foonji]

I bought the same type one over a year ago and it's still going strong, it spent most of its life under the sierra bonnet.

When I first got it, I removed the switch and plastic crap.

[fordem]

I have a different brand of cheap compressor - although I notice the cylinder head is a casting very similar to those shown.

Anyway - the switch on my compressor controls a relay which controls the motor - you might want to consider that, rather than switching a 36A load with a 6A switch.

[fritter]

Relay is a good way to go.

Especially if you're going to mount the compressor somewhere and switch it from the cabin.

I went for a quick fix the night before a trip.

Definitely recommend a higher rated switch though.

It's on my to do list.

[atari4x4]

Ziggy approves

the little white plastic cap thing that had the loose wire is the thermal overload cut out to stop the motor from cooking it's self when working hard.

[jonno_racing]

atari4x4 wrote:

the little white plastic cap thing that had the loose wire is the thermal overload cut out to stop the motor from cooking it's self when working hard.

ah ya dont need that

[oozuk]

Those twin motor compressors are a heap of shit!! I had one and it kept failing and pulling in excess of 50A + I stripped it down and ran twin core 6mm wire directly to the brushes and I got one trip out of it. Turned out the main shaft on the compressor was bent and it kept polling out. Also the alignment points of the motor bearing end plates were rubbish!! It was near impossible to ensure the motor was running true centre in the magnet assy.

Biggest waste of $90 ever, and to add to it, I modified the compressor my fitting larger flowing brass fittings to the compressor heads and hard wired and mounted to my Suzuki tray, so chance of refund was Nil.

[fordem]

atari4x4 wrote:

Ziggy approves

the little white plastic cap thing that had the loose wire is the thermal overload cut out to stop the motor from cooking it's self when working hard.

That little white plastic cap is nothing more than an insulated crimp splice - a metal sleeve in a plastic cap. You strip the wires, stick them in the sleeve, and then crimp the sleeve onto the wires with a pair of pliers.

If it were a thermal cutout it would need to be physically mounted to the motor (for heat transfer) before it would work - and it would have two crimp connections to the wiring.

[fritter]

fordem wrote:

atari4x4 wrote:

Ziggy approves

the little white plastic cap thing that had the loose wire is the thermal overload cut out to stop the motor from cooking it's self when working hard.

That little white plastic cap is nothing more than an insulated crimp splice - a metal sleeve in a plastic cap. You strip the wires, stick them in the sleeve, and then crimp the sleeve onto the wires with a pair of pliers.

If it were a thermal cutout it would need to be physically mounted to the motor (for heat transfer) before it would work - and it would have two crimp connections to the wiring.

That's correct. there's nothing else in there.

The idea is that you push the stripped wires in and twist the cap before crimping.

I prefer soldered.

[fordem]

For certain types of connection, a properly done crimp is superior to soldering - especially when vibration is expected - which is why the majority of terminal connections in a car are crimped.

When the molten solder wicks into the stranded wire it prevents it from flexing and the connection eventually breaks right at the joint.