Replace voltage regulator on 72T

wahoofan · 07-13-2005, 05:24 PM

I think I need a new voltage regulator on my 72T. Lots of the classic symptoms I've seen mentioned on this board.

Can I replace the VR itself, or will I need to replace the alternator as well?

techweenie · techweenie's Garage

It's a pretty easy replacement. I believe there are two types of VR/alternator used on the '72, so you need to be sure you get the right one. I think it's a screw or two and the actual connections.

There is also an alternator with an integrated VR, so if you could shoot a picture of the electrical panel (driver's side of engine compartment) and post it, we could probably give you some help right here.

pwd72s · 07-13-2005, 06:39 PM

Assuming all is stock...a big assumption these days, either a SEV Motorola or a SEV Marchal works...only the cover is different. Stock '72 alternators used the external V regulator...

wahoofan · 07-24-2005, 06:27 PM

Thanks for all the info! Does this picture help at all?

Early_S_Man · 08:04 PM

The regulator is mounted on the fuse/relay/CDI/electrical panel on the left side of the engine compartment [bolted to inner fender panel] ... under the black plastic cover secured by an M6 plastic wing bolt ... located aft of the CDI unit [with Yellow 'Vorsicht!' warning label with Red Lightning Bolts on it] ...

The alternator and regulator could be Bosch or SEV Marchal/Motorola ... but the regulators are each a distinctive shape, easily recognized in even a fuzzy pic! All '64 thru '73 regulators use screw terminals and lugs on the individual wires ... not the 3-pin plug used on 1974 & later cars!

RoninLB · 07-24-2005, 07:15 PM

SEV Marchal regulator from my stock '77

pa911 · 07-24-2005, 08:04 PM

I'm no expert, but it seems I read on here somewhere that it didnt matter what VR you use even one from the local auto parts store would work. is this correct?

Zeke · 07-24-2005, 08:09 PM

Quote:

Originally posted by pa911
I'm no expert, but it seems I read on here somewhere that it didnt matter what VR you use even one from the local auto parts store would work. is this correct?

Even if you got it to work (which it might), that is not correct. Buy the specified part. Electrical systems are a balance of amperage and voltage. A wrong battery can make a difference on some cars like British cars that have Lucas electrics. Get the right part.

Early_S_Man · 07-24-2005, 09:20 PM

Here is what all '69 thru '73 Marchal/Motorola regulators look like:

bigchillcar · bigchillcar's Garage

Quote:

The regulator is mounted on the fuse/relay/CDI/electrical panel on the left side of the engine compartment [bolted to inner fender panel] ... under the black plastic cover secured by an M6 plastic wing bolt ... located aft of the CDI unit [with Yellow 'Vorsicht!' warning label with Red Lightning Bolts on it] ...

warrenspeak translated: 'no..aim your camera more to the left..'

ryan

wahoofan · 07-25-2005, 07:34 AM

Thanks guys - Warren's pic looks exactly like what I just found when I opened the cover. So I just disconnect that thing and take it to the import parts place (owned by a guy with a 75 911s) and he should be able to hook me up, right?

wahoofan · 07-25-2005, 07:54 AM

Looks like this

wahoofan · 07-25-2005, 06:07 PM

Anyone know the Pelican part no. for this vr?

pwd72s · 06:53 PM

Aye, here's the rub: "They don't make 'em like that anymore." Maybe Warren can explain their innards a bit better, but evidently they can be adjusted for output somehow, and their points can be cleaned up, made to function again? There is also the used market...wrecked-em yards, parts for sale ads, ect...then you can send 'em off for a check-out refurbishment. I carry a few spares with me, thanks to suggestions made by Warren here. 1.. Spare Bosch CD unit, 2..spare V. Regulator, 3..spare coil. None of these easily found in small town USA, so it's good to have them...(edit) Frankly, just looking at the pic, which is no measure of function of course, your V. regulator looks pretty good. Have you plugged in a voltmeter, done any read-outs as you're driving? A cheapskate test gauge is a cheap multitester hooked to a male cigarette lighter plug...lay the unit on your seat or have a co-pilot give voltage readings as you drive...

Lorenfb · 08:28 PM

"Even if you got it to work (which it might), that is not correct." - Zeke -

Not true!

A regulator is a regulator is a regulator. Any regulator when connected properly
will function correctly. Just ask Derrick/Dieter @ Lomita 911 they'll confirm this,
as I've used many alternates for them. The key point is that the SEV Marchel
has a high failure rate with large capacity batteries AND regulators which set
the voltage to greater than 13.75 to 14.00.

The SEV Marchel 55 amp alternators (early ones with the red plates) are badly
designed with an additional output diode causing a higher internal voltage
resulting in additional power losses (internal heat). Typical power losses
at 50 amps:

Early with red plate - 50 X 3 x (~1.0 volt diode drop) = 150 watts
Late without red plate - 50 x 2 X(~1.0 volt diode drop) = 100 watts

Obviously, these losses exclude the stator winding losses which are significant.

An additional problem with this alternator design is the way the diodes are
pressed into the diode plates. Because of thermo mismatch of the steel
header of the diodes and the aluminum plates, the contact resistance increases
(diode to diode plate) with the greater expansion in the aluminum plates versus
the diode header. The 928 SEV Marchel 85 amp alternators had high failure rates
because of the same design flaw.

The SEV Marchel regulator is very reliable and can be easily adjusted to prevent excessive
currents on the old SEV Marchel 55 amp alternator. Max voltage @ battery S/B less than 13.75.

wahoofan · 07-26-2005, 04:27 AM

A little confused here - does this mean I can't replace my vr without doing the alternator, too? The sticker on my car specifically states that the alternator and regulator must be of the same manufacturer.

My only real symptom here is a crazy tach. I just wanted to go after the vr because it seemed a likely culprit and a cheap part to switch out.

bigchillcar · bigchillcar's Garage

dirty or worn ignition points will cause an erratic, jumpy tach as well..
ryan

pwd72s · 07-26-2005, 08:41 AM

Wahoo? I'd definitely say you need to do, or have done, some diagnostic work before you start to replace parts willy nilly...ryan made a good suggestion on the bouncy tach. Also, read my post on a voltage check.

cmcfaul · cmcfaul's Garage

My radar detector flashes and beeps HI VOlTAGE on my 73 911 e until the car is warmed up (battery charged I assume) or I turn the lights on. It is very annoying. I have offten thought of replacing the voltage regulator but is it normal for the early 911's to have higher voltage outputs then today's cars?

Chris 73 911 E
Bell Rador detector (new)

tobluforu · tobluforu's Garage

Your reg, like my reg should look like what warren posted. I bought a new one from pelican which in now covered in white plastic instead of metal.