How hot is OK for an alternator

[XLD]

My Leece Neville 140 Amp alternator is too hot to touch when running. Is that normal?

[Tracy D'arth]

Just now, XLD said:

My Leece Neville 140 Amp alternator is too hot to touch when running. Is that normal?

Yes. The insulation on windings is probably rated at 150 degrees C, the electronics are in the air flow, so providing it has a cool air source they will survive.  Is the alternator rotating in the correct direction for the fan to pull air in from the vents in the back?  The fans are not usually bidirectional.

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[nicknorman]

If it is charging hard (batteries fairly low) then yes. The interstices of an alternator can get up to about 150C under full load. “Too hot to touch” is over 60C or so which is not that hot. Obviously the hotter it is the shorter it’s life, so make sure engine bay ventilation is as good as it can be.

[Detling]

Drip of water or spit on the metal body, if it just evaporates you are fine ,if it spits and boils it is over 100C which is probably a sensible top temperature, if it balls up and rolls around furiously you will probably be to late as that is about 200C. 

 

[Jen-in-Wellies]

23 minutes ago, nicknorman said:

“Too hot to touch” is over 60C or so which is not that hot. Obviously the hotter it is the shorter it’s life, so make sure engine bay ventilation is as good as it can be.

The human hand is a poor measure of temperature over about 40C, the point at which you can't keep your hand there indefinitely, and especially over 60C, where you recoil almost straight away. You'd want some actual measurements, like an infrared thermometer (infrequent red on this forum!), or some liquid crystal strips.

For most electrical and electronic things, every 10C rise in temperature roughly halves the life of the gadget, until you reach a temperature where something actually melts, or burns, or decomposes.

Jen