compair 75 wont stop building pressure

by guy
(melbourne australia)

compair 75 compressor keeps building pressure to the point it cuts the 3 cylinder diesel motor out or overheats the motor,


i use it mainly to operate a jackhammer,any advice appreciated thanks, guy
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Guy, it sounds to me as though the unloader valve / throttle assembly needs work.

If your manual doesn't cover that, maybe a reader here can comment.

Cheers,

Bill

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Feb 23, 2012
compair 75
by: john

check the unloader diaphrams on the opposite side of the air intake for the compressor end and make sure that the air line from the reciver ( the end were the taps are ) has not come off there might also be a tap on this line so make sure it is open , or it will not let the signal air to the unloader through, find an on line manual for it , the air lines and fault giudes are there

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compair c29p stalling

by steve lawrence
(worcester uk)

hi i have a compair c29p it starts and produces plenty of air and when i close the oulet valves the unloader starts to move but the engine stalls . any ideas??

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1983 Compair holman compresser spits its hydro-lick oil out?

by Aaron kilkenny
(derby England UK)

hi iv got a 1983 100 psi compair holman road compresser with a welded air receiver fitted inside

the unit is over heating and spits its hydro-lick oil out out of the welded air unit

is there a filter i need to chage or certain oil i need for it? aaronkilkenny@live.co.uk or 00447971325098

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COMPAIR 150 - motor won't start under load once belt is attached?

by Shrew
(Nottingham, England)

Hi,

i have a COMPAIR 150, twin piston compressor, which is powered by a Lafert LM90 single phase 240v, 2.2kw, motor.

having bought it used, it initially worked fine, then began to struggle to start, within 24hours.

i found a 8mm bolt was used for a plug fuse! so upon putting this right, it simply blows a regular 13amp in an instant.

i replaced both the run and start capacitors, and have now replaced the motor start relay too, all for like for like parts, genuine where i could,

it will run on my bench, plugged into the nearest socket outlet, no problem at all, 100%.

so i remounted it on the compressor, attached the belt, wired it directly to the spur which is one the same circuit as the socket it was test plugged into, and approximately 10ft away, and it simply won't spin up, just stutters round, dimming the lights through current draw. there are no other major current draw appliances on the circuit.

take the belt off, starts up fine, changes over from start to run capactitor and winding in an instant, just a momentary dimming of lights and voila, she's up and running, 2800rpm,

the compressor turns by finger very freely, no out of the ordinary resistance at all, so i can't believe it is responsible for killing the efforts of a 2.2kw motor!

i have run the belt progressively slacker, to the point that i can peel it off the pulley by hand without adjustment to the tension, so can't be that.

I'm at a loss!

can it be as simple as its is right on the cusp of critical undervoltage/current supply to prevent loaded start up?

what amps should i expect this to draw upon start up?

please help bill????

i have spent a small fortune so far, a motor shop has tested my windings to satisfaction, and i'm no further forward and losing business!

aaaghhhhh!
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Hi Shrew.... aaaaghhhhh indeed!

I'm am puzzled though. I did some resarch on your air ocmpressor, and the Compair model number 150 only ever returned info on a tow-behind air compressor.

So, I know nothing about your model. :-) Having said that, and based on what you have done so far, here's what I would do next.

Empty the tank and pull and clean the tank check valve.

Ensure that the intake filter is pristine, and you might even try to run it without the filter to see if that might (remote I know( be the source of the problem.

The next area would be the intake and pressure valves (that's a teardown, unfortunately) and if none of these are the issue, then I would surmise you have a load related pump failure.

Sorry.

Bill


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Jun 09, 2012
Cap Test.
by: Anonymous

You can test a capacitor with a multimeter set on ohms. You will see your meter giving a reading, increasing untill infinity, reverse the meter leads on the capacitor and the reading should also reverse. Check it first on your run cap so you can see it happen.

_________________
And, you could also see the page on this site for instructions on how to test a cap too.

~B.

Feb 14, 2012
More Info - old motor fires into life no questions asked
by: Shrew

Hi Bill, thank you for your response, and here is an update for you.

i have re-attempted from an empty tank, no change at all.

i removed the motor to bench test yet again, but before i did any testing, i fitted my old old old motor from my last compressor,

this motor is probably half the horspeower, Kw, and rpm, but it fires into life no questions asked,

so does this eliminate the air pump, and valve issues you mentioned?

i hope so, cos i know little about the lafert motor, but even less about compressor pumps!


so, back to my bench testing, right now, i would say that according to my multimeter, which has a capacitor test option, the 40uf run cap comes in at 41.34uf, fab! but the start cap, zilch! and i should be getting 130-150uf according to the label.

but this is brand new, surely it hasn't failed already?

is there a condition that can blow ther starter capacitor so quickly?

do you have any advice on identifying and testing the winding tails that come through into the terminal box?

cheers

shrew
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Well, if you changed the motor and it ran the compressor perfectly, that pretty much rules out a mechanical issue on the pump.

I don't fix motors, I do not profess to be an electrician, so you and I both will have to wait and see if a knowledgeable visitor can help with your other questions.

Clearly though, from what you've written, it's the cap or motor that's the problem.

Cheers,

Bill



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