General generator question 500N 1958-59

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General generator question 500N 1958-59

mimmo

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finished up the interior and now the generator light came on! Car was parked for some time so i'm hoping its just the brushes. Output voltage is erratic but the most i can read is 4 volts. I've removed the top cowling, fan nut, strap, nuts holding it to the cowling but other than a small amount of movement i can not get it free from the cowling. The fan is free on the shaft. Am i missing something or is it just frozen in place?
 

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mimmo,

The generator is held on to the tinware with two bolts as well as being secured by the mounting strap. If you've removed them plus the impeller and fan belt, it should just come out.

According to the information that I have the generator should develop ~14V at anything above 3000rpm (~ 1500rpm engine revs). Early cars (engine numbers up to 056195) were fitted with 180W generators with later ones fitted with 230W units. If yours is only reading 4V at a reasonable engine speed, it needs a service. Bearings and brushes are available and cheap. Armatures are also available, but hopefully that bit is OK.

Chris
 
thank you Chris,
Looks like mine is the older type (motor 043658).

I've removed what you described, I'll give it another try tonight. i can already feel some movement on the front bearing so will have to replace. Where are folks buying the brushes. I was going to pickup the closest size brush i could find and filing for fit.
 
Turns out the generator must be pulled up and out of the cowling as opposed to sliding it straight back and out of the cowling.
The brushes are in great shape. The armature seems ok too, all communicators tested fine. Anyone know if the field windings should have resistance, mine has very little resistance.
The generator spims up easliy when hooked up to a 12v battery but only generates 1.2v at about 2000rpm.

thanks
 
mimmo,

I've attached a couple of output graphs taken from the shop manual. The earlier generators should put out about 8A at 2000rpm.

Resistances are measured at 20degC (68degF) and are 0.145 (+/- 0.01) ohms for the armature and 8 (+0.1, -0.3) ohms for the field winding. This applies to both the 180W and the later 230W generators.

The manual gives the following trouble shooting guide for a system where the warning light does not go out even at high rpm:

1) broken connection between terminal 67 of generator and terminal 67 of regulator
2) oxidised or dirty regulator contacts
3) internal regulator contacts broken
4) broken or grounded field winding
5) broken or grounded armature winding
6) worn brushes
7) dirty commutator

If the warning light does go out but only at high rpm, the following:

1) short circuited field windings
2) field winding grounded to frame
3) large number of armature windings shorted

If this is the case then the problem needs to remedied as soon as possible or the voltage regulator may be damaged by the abnormally high excitation current that results from the low field winding resistance.

The manual also gives advice where the warning light glows feebly at highish rpm. In this case it is the bulb that is a fault - it is glowing at too low a voltage.

Some of this sounds bad, but I'm sure you'll get it sorted.

Hope all this helps,
Chris
 

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Thanks for the info Chris, this helps.

I'm sure theres something a miss with this generator , I should be getting 12volts at 2000 rpm. The field windings are measuring 6.7 ohms at 72F, which is below spec but i'm not sure if that would result in only 1 volt at 2000 rpm and 3 volts at 3000rpm. Thanks to your info i'll measure the armature resistance now.

In the meantime i'm having a generator sent from a breaker in Italy. Need to get this car back on the road.
 
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