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| Small ¾ hp portable air compressor problem (Page 1/2) |
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williegoat
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APR 02, 06:27 PM
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This is an old Campbell-Hausfeld “Power Pal” model MT5001.
I have had this compressor for about 30 years and had not used it in probably over 10 years.
I replaced the pressure switch because it was bad. I also replaced the unloader valve, regulator and check valve.
It will build pressure but will not restart unless I empty the tank. This is why I replaced the check valve.
The unloader valve seems to be working. I can hear it.
Also, I think the check valve is working because if I remove the unloader line with a full tank and the motor not running, there is no pressure there.
With any pressure at all in the tank, the motor struggles and will not start, but starts fine after I bleed off the tank.
What am I missing?
I should have just donated it, but now I have spent about $60 in parts and the damned thing is sitting in the corner laughing at me.------------------
"Don't shoot me, Joe!"
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Marko
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APR 02, 06:55 PM
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Could it be a weak starter capacitor on the motor ?
Not giving it a big enough whallop to get the armature turning under a small load, but it turns under no load ?
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williegoat
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APR 02, 07:04 PM
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| quote | Originally posted by Marko:
Could it be a weak starter capacitor on the motor ?
Not giving it a big enough whallop to get the armature turning under a small load, but it turns under no load ? |
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Thank you for your reply.
You know, that was going to be my next guess, but I don't know where it is. I don't find it in any parts list/diagram, so I might have to do some exploratory surgery.
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IMSA GT
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APR 02, 10:53 PM
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| quote | Originally posted by williegoat:
Thank you for your reply.
You know, that was going to be my next guess, but I don't know where it is. I don't find it in any parts list/diagram, so I might have to do some exploratory surgery. |
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Unfortunately it may be IN the motor.
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Marko
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APR 03, 01:34 PM
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williegoat
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APR 03, 04:33 PM
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Yes, thank you. I will probably tear that front plate off tomorrow.
I have a bigger compressor in the garage, but I thought it would be nice to have this little one out back for blowing the dust out of computers, cleaning my bicycle, etc.
I can still fire it up and fill the tank, then shut it off so it doesn't try to start and burn something up.
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williegoat
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APR 03, 07:33 PM
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I took the front cover off the motor and there is nothing to see in there, so I will use it like it is for now. It is not something I need, I was just bored.
Thanks to everyone for your help.
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theogre
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APR 03, 10:18 PM
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The bleed valve, the one opens when compressor is off, may seem to work but can have wrong/bad "check valve" and Compressor still sees full pressure and won't start.
In this case will burn start coils and switch that runs it.
bv is often a "T" on cv but should be:
comp-----bv----cv---tank
Start coil or switch is likely burn or have crap in the switch.
Quick look at pdf doesn't use start or run caps.------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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williegoat
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APR 03, 11:18 PM
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| quote | Originally posted by theogre:
The bleed valve, the one opens when compressor is off, may seem to work but can have wrong/bad "check valve" and Compressor still sees full pressure and won't start.
In this case will burn start coils and switch that runs it.
bv is often a "T" on cv but should be:
comp-----bv----cv---tank
Start coil or switch is likely burn or have crap in the switch.
Quick look at pdf doesn't use start or run caps.
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The unloader valve T's off of the discharge line just upstream from the check valve, just as it was originally designed. Both valves are new.
As I described above, when I disconnect the unloader tube from the unloader valve, there is no bleed from the check valve, so the check valve is holding pressure in the tank as it should. After reconnecting the tube to the unloader valve, the motor will still struggle when there is any pressure in the tank. Both valves are new and are functioning properly.
The switch is also new and is functioning properly. It will start when the tank is empty, and shuts off when the tank reaches about 92 psi (I dialed it down from the original cutoff setting of 120). It cuts back in at about 45 psi, but cannot run against the pressure. If I bleed the tank back down, it will again fill it to the cutoff pressure.
As I said above, I could not find any caps in the diagram and could not find any by visual inspection.
This compressor only cost about $150, 30 years ago and I have certainly got my money's worth out of it over the years. I am just the kind of guy who hates to throw something away if it can still be of use to someone.
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theogre
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APR 04, 02:16 PM
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there is a Switch Inside the motor that should run the Starting coils. Item 32.
Not external switch that sets max pressure and trips the bleed/blowoff valve in many compressors.
Even if the 32 switch is new, can have iffy start coil and fail to start right.
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