Charge light resistor

[Oldbrowntarga]

1981 sc getting Valeo alternator. Have studied factory service bulletin and am comfortable with the install. Question is, does the Valeo #432776 still require a resistor added to the charge light bulb? Host doesn't offer one or mention this modification in product info.
Thanks in advance.
Philip

[speednme1]

I don't know about a resistor but there is a Diode
https://www.digikey.com/en/products/detail/onsemi/1N4006/976986

[famoroso]

What's the service bulletin number?

I just had a Valeo installed in my 1987. If it needs something else, I'd like to sort that out.

[timmy2]

You will be fine Frank as your ‘87 was an internal voltage regulator already.
For external VR models you place a 91 ohm (100 will work) 5 watt resistor across the charge lamp wires to add a load so the internal regulator will activate and charge the battery.

[famoroso]

Originally Posted by timmy2

You will be fine Frank as your ‘87 was an internal voltage regulator already.
For external VR models you place a 91 ohm (100 will work) 5 watt resistor across the charge lamp wires to add a load so the internal regulator will activate and charge the battery.

Roger that. Thanks!

[mike sampsel]

Originally Posted by timmy2

You will be fine Frank as your ‘87 was an internal voltage regulator already.
For external VR models you place a 91 ohm (100 will work) 5 watt resistor across the charge lamp wires to add a load so the internal regulator will activate and charge the battery.

I have not added the 91 ohms to mine, the alternator gets my battery voltage up to 14 volts, with AC on, and headlamps and fogs and rpm at 1200, below 1000 the voltage goes to about 12 volts as expected so it seems to be charging fine.

I wonder if I should add the resistor anyway?

[spoke]

Originally Posted by mike sampsel

I have not added the 91 ohms to mine, the alternator gets my battery voltage up to 14 volts, with AC on, and headlamps and fogs and rpm at 1200, below 1000 the voltage goes to about 12 volts as expected so it seems to be charging fine.

I wonder if I should add the resistor anyway?

The resistor is just there to provide more current to get the alternator started. It's called bootstrapping as the GEN light provides some current to the rotor of the alternator to start the alternator. The resistor is to provide more current to make sure the alternator gets started. If your alternator starts up every time then you may not need the resistor. If you start your car and the GEN light stays on until you rev the engine, then the resistor is needed.

[Oldbrowntarga]

As it turned out, no resistor was needed because I was unable to locate a new Valeo alternator anywhere.
The problematic Paris Rhone alternator had been rebuilt 2 years ago but was intermittently
overcharging. Two Porsche shops pointed to the voltage regulator as the problem but I had previously tried other regulators and the problem remained.
After bending a few ears at a local PCA sponsored cars and coffee, I got a referral to a rebuild shop, Chelmsford Auto Electric in Tyngsboro, MA.
Took alternator in this past Monday, picked it up and reinstalled on Wednesday. Put on over 250 miles and it performs perfectly.
Just wanted to take a moment to highly recommend this shop to those of you that may need rebuilding services in the future.

[mysocal911]

Originally Posted by Oldbrowntarga

1981 sc getting Valeo alternator. Have studied factory service bulletin and am comfortable with the install. Question is, does the Valeo #432776 still require a resistor added to the charge light bulb? Host doesn't offer one or mention this modification in product info.
Thanks in advance.
Philip

Should have just rebuilt the original SEV Marchell 70A alternator, i.e. external regulator, which was very reliable.

Note: Paris-Rhone and Valeo are the same alternators.

[Walt Fricke]

Dave - do you mean the Marchall is very reliable, or the external regulator which serves it? My '77 911 had an external regulator, and I am fairly sure it was of the coil and points variety. I think those are subject to the problems old distributor points of the era had - pitting and so on. Or had Porsche changed to solid state external VRs?

On my hot rod track car I am using an older alternator, and use a solid state external VR from a 914. Small, light, and works just fine. Might just be dumb luck that it matches what the alternator needs, though.

[mysocal911]

Originally Posted by Walt Fricke

Dave - do you mean the Marchall is very reliable, or the external regulator which serves it? My '77 911 had an external regulator, and I am fairly sure it was of the coil and points variety. I think those are subject to the problems old distributor points of the era had - pitting and so on. Or had Porsche changed to solid state external VRs?

On my hot rod track car I am using an older alternator, and use a solid state external VR from a 914. Small, light, and works just fine. Might just be dumb luck that it matches what the alternator needs, though.

Both! The good point of an external regulator is that one can always isolate a charging problem easier, i.e. reg or alt.
Plus, the mechanical reg can always be repaired and adjusted to whatever voltage you want.

[Oldbrowntarga]

My mistake on the brand if my alternator, it is indeed an SEV Marshal. It is the unit originally fitted to the car at the factory as I have owned this targa since new.
Sorry for the mixup.

[LM3929]

this is what you are looking for

Lorne M.

[al lkosmal]

Here is a link to an earlier discussion regarding the change from external to internal regulater type alternators.

https://forums.pelicanparts.com/porsche-911-technical-forum/989178-electrical-wizard-help-needed-alternator-light.html