Why is my solenoid real hot?

[Bartso]

i was using a heavy duty solenoid there was practically no load going through it and it kept playing up sometimes it would engage sometimes it wouldn't checked everything voltages are where they are spose to be but the solenoid was too hot too touch.
Is this a bad earth, thing is though it is earthed with everything else and everything else works

[-ET 4wd-]

G'day Bartso,
All i know is heat in electrics means resistace so im guessing if the solinoid is new check the motor itself may have cr@p in the brushes or they are on the way out or the field coils are rusty from copping a drink of mud.

Pull the thing out pull it apart clean it all out and see how that goes if no good ditch it and try a new one to eliminate voltage as the problem.

Also try thicker cable to the starter. and maybe a 30 amp relay wire to the solinoid wire, had to do that on hot chevs to start them when they got warm (drag racing trick)

Good luck,

Steve.

[F'n_Rover]

Put a meter across the contacts when its activated and loaded up, you dont want to see much.

You could also try disconnecting the load from the solonoid. See if it still gets hot when activated, if not its arcing causing the heat. This is bad.


If it still gets hot, its just the coil. BTW has the coil got a wattage rating ?

[-Scott-]

This is a little wierd.

If you are using the solenoid within it's ratings, without excessive load through the contacts, it's difficult to understand why it's getting hot.

Any parasitic resistance in the coil circuit will reduce the total current draw, so total power dissipation (V x I) will be lower - not higher.

Using the wrong coil voltage will cause over-heating, but intermittent pull-in suggests your voltage is on the low side.

Theoretically it's possible that your contacts are arcing at high frequency: borderline voltage will only just pull in the coil, causing the load to switch on. Increased load on battery reduces battery voltage below the hold-in value, so the contacts open again. Voltage rises, coil pulls in, contacts close, battery voltage drops again. And so on. IF this is happening (long shot) arcing of the contacts will create excess heat, and an in-line ammeter is likely to measure a low DC current. IF this is happening, you may be able to measure a high AC current through the points, or a significant AC voltage across the contacts.

Another possibility is heat-sinking. It's possible the coil is a high power design, relying on the coil being firmly mounted to the vehicle body/chassis in order to dissipate heat. If it's only sitting on your bench, that may explain the heat - but doesn't explain the intermittent pull-in.

Got any links to a website for your solenoid?