P38A Intermittent EAS Pump Thermal Switch

pwood999 · Jan 12, 2017

Was taking a long time to go from Motorway to Standard height this evening, so put Nanocom on when I reached my destination, and found the EAS telling me pump had overheated. Checked under the bonnet and it's stone cold. Ran the pump manually for 10mins to get enough air for the ride home.

At home the thermal switch says normal again, and the pump is running ok. Damn thing must have gone intermittent tonight

Lucky I have a spare thermal switch somewhere . . . just gotta find it and fit it this weekend.

Grrrrrr · Jan 12, 2017

Yes, those thermal switches can be a bit tempermental. I had a dodgy once once.

wammers · Jan 12, 2017

More than likely a dry solder joint. P38 electrics seem to be full of them.

pwood999 · Jan 13, 2017

Took the compressor apart today. It wasn't the thermal switch or a dry joint. The braid that connects the motor brushes was fouling on the brush springs, causing intermittent contact with the armature. Freed it up & reassembled, and now the motor runs reliably with good reading from thermal switch.

While it was out, I also renewed the piston ring & several seals (had spares in garage). Old ring was fairly loose in the cylinder, although not completely worn.
EAS working again.

tomcat59alan · Jan 14, 2017

[QUOTE="pwood999, post: 3906184, member: 6010
Old ring was fairly loose
You talking about Holiday Chicken ?

pwood999 · Jan 14, 2017

well it easily dropped down the hole when letting go

wammers · Jan 14, 2017

Incorrect or careless refitting of brush holder to compressor can result in brushes hanging on snagged braid causing the brushes to lose contact as they wear.

pwood999 · Jan 14, 2017

wammers said:
Incorrect or careless refitting of brush holder to compressor can result in brushes hanging on snagged braid causing the brushes to lose contact as they wear.

Yes, that's what the loose ring inside seems to be useful for (although only on some pumps). The smaller lip holds the brushes back nicely while fitting the end cap, and then pops off next to the bearing as the armature contact slide between the brushes. Trouble is, I have one pump where the ring doesn't fit through the PCB hole, but others where it does this job perfectly

P38A Intermittent EAS Pump Thermal Switch

pwood999

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

wammers

No longer with us, RIP

pwood999

Well-Known Member

tomcat59alan

Well-Known Member

pwood999

Well-Known Member

wammers

No longer with us, RIP

pwood999

Well-Known Member

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