EAS Compressor Overheat

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rasheed

rasheed

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Splitting this off my previous thread as related but slightly separate issue. Got hold of a pressure meter which we Tee'd between the compressor and the reservoir. Found that compressor cuts out at 9.5bar which is fine. Some people say it should be 10bar but that might just be my meter. If we deliberately let some air out the compressor will kick in again at about 7 bar. So I assume pressure switch is fine. On the other hand when lowering the car to access and raising back to extended it depletes the tank obviously and pressure drops to about 5 bar. Now when the compressor comes on it doesn't manage to get the pressure back to 9.5 bar in one go. Instead it overheats and cuts out for 3 minutes (so temp switch also fine), then after a rest it starts again and we get to 9.5. There's no air leaking from the exhaust and you can't keep your thumb on the compressor out line (blue) for more than a couple of seconds. Soapy water test on all connections found no leaks.

My question, doesn't it seem to be overheating a little quickly? Ambient temp about 30 degrees and car stationary so while engine fans blowing and EAS box lid off, no driving airflow (whether that makes a difference?).

Why might it be overheating so soon? I would guess from the above that there are no internal leaks, it just doesn't like running for more than 5 or 6 mins before taking a rest. Could it be that actual motor components getting too hot? How is it actually meant to be kept cool? Your kind thoughts gentlemen!
 
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either your exceeding it's duty cycle due to wear causing it to be less efficient or the thermal switch has gone faulty
 
Wammers has beaten me to it.
Badly worn brushes or commutator would cause the motor to overheat, assuming that your thermal switch is o.k. You might want to start with a thermometer.
 
Cheers fellas, was leaning in that direction so its good to have you concur. Dogsbody, I have an IR thermometer (somewhere!) should I take readings straight off the barrel or somewhere else and what sort of readings would be considered normal?
 
rasheed said:
Cheers fellas, was leaning in that direction so its good to have you concur. Dogsbody, I have an IR thermometer (somewhere!) should I take readings straight off the barrel or somewhere else and what sort of readings would be considered normal?
Click to expand...

I've never measured one and haven't got an IR thingummy.
Hang on I think SWMBO has got a cooking thermo somewhere, back in a bit.
 
Well that's me sleeping in the spare room for a while - and where the hell do I buy a new cooking thermometer?
Anyway it was all a waste of time because my pump hardly gets warm, mind you it is only a few months old.
Sorry mate but at least Datetek came riding to the rescue - again.
 
Dogsbody's in the Doghouse because of my compressor! :eek: You're a good egg DB but ya shouldna outta done it! Almost feeling guilty now. Will down the rest of this beer in your honour, friend. :beer2:
 
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wammers said:
Problem with the brush gear/commutator or rear bearing i would think Rash.
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There's a little brass socket right at the back into which the shaft fits. Should that be tight onto the shaft (ie should it turn with the shaft) or is it just a pocket and the shaft should turn freely inside it? I ask because there is some play and I don't know if its meant to do that.
 

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rasheed said:
There's a little brass socket right at the back into which the shaft fits. Should that be tight onto the shaft (ie should it turn with the shaft) or is it just a pocket and the shaft should turn freely inside it? I ask because there is some play and I don't know if its meant to do that.
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Brass bush is a sintered oilite bearing there should be a pad behind it to hold oil. It should be held tightly by cage and not turn freely within it. If shaft has been tight in bearing and bearing has been turning within cage you will need to sort that or get a new back plate. Shaft should turn freely in bearing. If if all else is good but shaft is tight clean it with some 600 wet or dry until it is free then apply some oil to bearing and pad behind it. Clean commutator with same wet or dry grade, it looks ok from photo and reassemble.
 
rasheed said:
Shaft turns freely. Can't see any pad though.
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Sintered bearings are pourous pressed from powder then cooked then soaked in oil. Usually they will have a felt pad behind them as an additional oil storage. The compressors have a known fault that the bearing becomes loose in their cage or the cage breaks away. If the bearing is tightly held by the cage and needs force to move it then it will be ok. Shaft should be a snug fit in bearing without being tight. Can't see anything in photo that would cause overheating or any sign of it to be honest.
 
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gfromleeds said:
Ahh your getting into teratory were id just get a new one
Im not into the little fiddly stuff just give me a big hammer any day
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nah its half the fun of ownership. soon with the help of this forum i'll be able to build a P38 from some cereal boxes, milk tops and string but I might need to ask a grown-up first.

wammers said:
Sintered bearings are pourous pressed from powder then cooked then soaked in oil. Usually they will have a felt pad behind them as an additional oil storage. The compressors have a known fault that the bearing becomes loose in their cage or the cage breaks away. If the bearing is tightly held by the cage and needs force to move it then it will be ok. Shaft should be a snug fit in bearing without being tight. Can't see anything in photo that would cause overheating or any sign of it to be honest.
Click to expand...

Thanks ever so much Tony. Am replacing the brushes and rebuilding. Might put a dab of grease on the tip of the shaft for luck but that's about it. I did find the aluminium cylinder on the compressor end was a little worn and perhaps not sealing absolutely perfectly so as I have a new one on hand that'll be changed too. Piston ring seal seems fine and appears to seal well with the new cylinder. So no major repairs but the "pit-stop" can't have hurt. Will let you know how it all runs tomorrow.
 
Sorry, should have closed this thread. The little servicing and replacing the cylinder has done the job. Runs quiet, fills tank fast, all good. Been moving house this last week, loading it to the gills, lower and raising from access height, self-leveling and all the rest and worked just like it says on the box.

Thanks for the tip on the orange wire though. Sure I'll need it for next time!
 
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