Bosch alternator varnish / paint experts required! - PeachParts Mercedes-Benz Forum

Stretch · #1 02-16-2011, 09:58 AM

G'day All,

Mad question:-

Does anyone know what sort of paint I should be using on the internal parts of a Bosch alternator?

At the moment on top of the insulating varnish there is a red primer-like coating. Does anyone know if this is just normal red oxide or not?

JohnS · #2 02-16-2011, 10:08 AM

The red paint is a red insulating varnish. It is often referred to as Glyptal, which is a trade name, there are others. It is also commonly used to paint internal engine parts as a way of covering porosity. You can probably get it at a hot rod supplier, Eastwood may even carry it. The clear insulating varnish is a specialty product, in industry, if a winding needs to be touched up, you would use an aerosol generically called "air dry varnish" (air dry as opposed to baked, which is the way the varnish is dried when the unit was manufactured). Grainger carries both these products in their Sprayon brand. That would be red insulating varnish and clear insulating varnish respectively.

Stretch · #3 02-16-2011, 10:16 AM

Quote:

Originally Posted by JohnS

The red paint is a red insulating varnish. It is often referred to as Glyptal, which is a trade name, there are others. It is also commonly used to paint internal engine parts as a way of covering porosity. You can probably get it at a hot rod supplier, Eastwood may even carry it. The clear insulating varnish is a specialty product, in industry, if a winding needs to be touched up, you would use an aerosol generically called "air dry varnish" (air dry as opposed to baked, which is the way the varnish is dried when the unit was manufactured). Grainger carries both these products in their Sprayon brand. That would be red insulating varnish and clear insulating varnish respectively.

Thank you very much.

The internet is amazing when you know the correct key words.

Here it is

http://www.kpg-industrial.com/products/insulating_varnish/

and here

http://www.sprayon.com/products/red_insulating_varnish

funola · #4 02-16-2011, 11:22 AM

Hey Army, you going off the deep end restoring the inside of an alternator?

Alternators are also wound with enameled wire aka magnet wire.

"Enameled wire is wire (such as magnet wire) coated with a very thin insulating layer. It is used in applications such as winding electric motor coils, speakers and transformers. It is also used in the construction of electromagnets and inductors.

The core material is copper or aluminum, coated with a thin layer of a polyurethane, polyamide, or polyester etc resin - the so-called "enamel". Aluminum is lighter than copper, but has higher resistivity."

macdoe · #5 02-16-2011, 12:26 PM

Hello, What would be an effective and safe cleaner to use on the internal parts of an alternator before using the primer and varnish when restoriing the internal parts of an alternator?

Stretch · #6 02-16-2011, 01:45 PM

Quote:

Originally Posted by macdoe

Hello, What would be an effective and safe cleaner to use on the internal parts of an alternator before using the primer and varnish when restoriing the internal parts of an alternator?

I'm being careful with brake cleaner and before I spray on some new varnish I'm going to use that Eastwood pre-paint stuff.

I'm not 100% certain it will stick as I haven't tried it yet.

Stretch · #7 02-16-2011, 01:47 PM

Quote:

Originally Posted by funola

Hey Army, you going off the deep end restoring the inside of an alternator?

Alternators are also wound with enameled wire aka magnet wire.

"Enameled wire is wire (such as magnet wire) coated with a very thin insulating layer. It is used in applications such as winding electric motor coils, speakers and transformers. It is also used in the construction of electromagnets and inductors.

The core material is copper or aluminum, coated with a thin layer of a polyurethane, polyamide, or polyester etc resin - the so-called "enamel". Aluminum is lighter than copper, but has higher resistivity."

Yes indeed - that's the next one.

This time I'm even going to include some new fangled elctrickery testing with one of them new fangled multimeters...

...the luddite is getting a bit more technical this time as it looks like my rotor has been hitting my stator!

Johnt49 · #8 02-16-2011, 04:01 PM

Glyptal is good stuff, but overkill for your application.
Been using this for years. I've built hundreds of starters & alternators over the last 30 years and usually use a parts washer with mineral spirits for cleaning.

layback40 · #9 02-16-2011, 07:02 PM

Quote:

Originally Posted by Army

Yes indeed - that's the next one.

This time I'm even going to include some new fangled elctrickery testing with one of them new fangled multimeters...

...the luddite is getting a bit more technical this time as it

New bearings needed!! Dont use cheap ones. I think there is still a grade for alt bearings. They spin fast !!
The original varnish is a thermo set product & so should handle most cleaning solvents. Petrol is fine for cleaning it.

Stretch · #10 02-17-2011, 03:24 AM

Quote:

Originally Posted by layback40

New bearings needed!! Dont use cheap ones. I think there is still a grade for alt bearings. They spin fast !!
The original varnish is a thermo set product & so should handle most cleaning solvents. Petrol is fine for cleaning it.

Yeah may be - having had another look at it today I get the feeling that I've got a re-manufactured unit that has had bad bearings before... what I'm saying is that I can not detect any play by hand. When I reassemble it I'll measure it. Thanks for the tips.

Stretch · #11 02-17-2011, 03:25 AM

Quote:

Originally Posted by Johnt49

Glyptal is good stuff, but overkill for your application.
Been using this for years. I've built hundreds of starters & alternators over the last 30 years and usually use a parts washer with mineral spirits for cleaning.

Thanks for the information. Do you have any other tips?

layback40 · #12 02-17-2011, 06:36 AM

Quote:

Originally Posted by Army

Yeah may be - having had another look at it today I get the feeling that I've got a re-manufactured unit that has had bad bearings before... what I'm saying is that I can not detect any play by hand. When I reassemble it I'll measure it. Thanks for the tips.

If you are not replacing the alt bearings when its apart, best at least, if you can prize one of the covers off without damaging each one & add some grease to the bearings.

Stretch · #13 02-17-2011, 10:04 AM

Quote:

Originally Posted by layback40

If you are not replacing the alt bearings when its apart, best at least, if you can prize one of the covers off without damaging each one & add some grease to the bearings.

Good point - I'll see what I can do.

I expect that once "we've" sorted out that measuring timing with the glow plugs method my engine will run so smoothly I'll be able to hear a faulty alternator bearing...

(Small print - this is a smart arse European being sarcastic)

Stretch · #14 02-19-2011, 01:43 PM

I've been PMing Johnt49 about the subject of coating varnish on alternators (I understand he's pretty experienced!) and here's what he has to say:-

QUOTE:-
"There's no hard & fast rules about using varnish. It obviously isn't going to have the insulating properties of the original applied by the manufacturer, but when in doubt or where you can see the need go ahead & use it. When I was rebuilding for resale I always used it because customers wanted to see every part had received the "re builders attention". For my own use I use my own discretion.

I usually coat alternator stators just because they are the most stressed part of the unit. Don't apply it too thick or you could have a clearance problem with the rotor & cause the windings to retain too much heat. You hardly ever see a rotor drag against the stator because the rotor runs on ball bearings instead of bushings that will wear & cause miss alignment. The stators are prone to over heat when too much is demanded of the alternator (charging dead batteries, jump starting, not replacing a weak battery, etc) Alternators are designed to maintain a fully charged battery, not be a "battery charger".

" END QUOTE!

layback40 · #15 02-19-2011, 06:39 PM

Quote:

Originally Posted by Army

I've been PMing Johnt49 about the subject of coating varnish on alternators (I understand he's pretty experienced!) and here's what he has to say:-

QUOTE:-
"There's no hard & fast rules about using varnish. It obviously isn't going to have the insulating properties of the original applied by the manufacturer, but when in doubt or where you can see the need go ahead & use it. When I was rebuilding for resale I always used it because customers wanted to see every part had received the "re builders attention". For my own use I use my own discretion.

I usually coat alternator stators just because they are the most stressed part of the unit. Don't apply it too thick or you could have a clearance problem with the rotor & cause the windings to retain too much heat. You hardly ever see a rotor drag against the stator because the rotor runs on ball bearings instead of bushings that will wear & cause miss alignment. The stators are prone to over heat when too much is demanded of the alternator (charging dead batteries, jump starting, not replacing a weak battery, etc) Alternators are designed to maintain a fully charged battery, not be a "battery charger".

" END QUOTE!

Army,
Thats good advice.
Down here, any alts that are of the open design like you find on a car, that we have on equipment like tractors that work in dusty conditions, get the inside of their alts "sand blasted" as the fan draws air through for cooling. All the exposed wire ends up bright shinny copper. Any time an alt is off, we get the insides re-varnished by an electric motor re-winder.
We have an old scraper that is electric steer & elevator. Every few 1000 hrs of use its electric motors need re-varnishing. It runs over 400v 120 hz so any insulation break down would probably cause lots of sparks, maybe a tingle in your hands too.