Help me fault find my air compressor

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elpenguino

3392 posts

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#284199 6-Apr-2021 20:00

Gzers,

I'd appreciate your advice. I inherited this compressor which is a nice compact unit although the tank looks like mebbe 6-9 litres.

The problem, it does not increase the tank's air pressure according to the little gauge.

When the motor runs, the gauge doesn't move - not even a little bit.

What I have done so far is disconnect the pipe from the compressor head, circled in red. When I ran the motor with my thumb over the outlet, I could feel a little pressure building under my thumb.

Should I feel LOTS of pressure? i.e. should the compressor blow my thumb off the pipe?

If it's not the compressor I'm not sure where to look next.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

gzt

17003 posts

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Lifetime subscriber

#2687533 6-Apr-2021 20:05

Broken gauges are common.

SomeoneSomewhere

1787 posts

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Lifetime subscriber

#2687540 6-Apr-2021 20:26

The pressure switches often have a pipe going to them for an 'unloader valve' - this empties the pressure out of the compressor itself (but not the tank) when it stops, so the motor can start easier when it cycles again. If that valve gets stuck open, you'll never build up pressure, but you should hear hissing.

You should be able to build up noticeable pressure with your finger on the output pipe even just spinning the motor by hand. You might be able to pull the cylinder head and check the valves appear to be OK.

elpenguino

3392 posts

Uber Geek

#2687542 6-Apr-2021 20:29

gzt: Broken gauges are common.

When I undo the water drain plug on the tank there's no hiss. Not even a little bit.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

Bung

6402 posts

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#2687544 6-Apr-2021 20:32

If you aren't getting any pressure there won't be anything for the gauge to measure. It could be a broken reed valve. See https://www.about-air-compressors.com/make-your-own-compressor-reed-valve/ for ideas.

elpenguino

3392 posts

Uber Geek

#2687545 6-Apr-2021 20:37

SomeoneSomewhere:
The pressure switches often have a pipe going to them for an 'unloader valve' - this empties the pressure out of the compressor itself (but not the tank) when it stops, so the motor can start easier when it cycles again. If that valve gets stuck open, you'll never build up pressure, but you should hear hissing.

You should be able to build up noticeable pressure with your finger on the output pipe even just spinning the motor by hand. You might be able to pull the cylinder head and check the valves appear to be OK.

On this one, the silver pipe goes directly from the head to the tank, then branches off to the pressure switch (orange).

Does that mean it can't have a unloader valve?
I can examine more closely for one, now I know they're a thing.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

elpenguino

3392 posts

Uber Geek

#2687546 6-Apr-2021 20:40

Bung: If you aren't getting any pressure there won't be anything for the gauge to measure. It could be a broken reed valve. See https://www.about-air-compressors.com/make-your-own-compressor-reed-valve/ for ideas.

Ok, might be time to take the head off. After reading the page.....

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21