1974 2.7 Alternator Problem
 

All,

I have a '74 2.7 that is having charging problems. The car has the stock Marchal alternator that was rebuilt about four years ago. The car has seen very limited use since then, usually once or twice a month.

Having a dead start last week, I put the trickle charger on the battery while it was still connected in the car (2amp rate). After what i thought was a complete charge, the car cranked and ran, however going around the block i noted the GEN light was glowing red, a telltale sign of an issue.

The battery out of the car reads 11.8 volts. While in the car and running, the voltage was about 9.9 volts.

I believe this indicates a problem with the alternator which has a built-in voltage regulator in this model.

I have two questions for the group:

1) could the charging of the battery in the car damaged the voltage regulator?

2) it was a true pain trying to find a rebuilder for the Marchal unit in 2008-9. Does anyone know of a reliable rebuilder? I am in North Carolina

The car has a fan shroud model #901.106.101.5R - when the Marchal gave out the first time, I ordered a replacement Bosch unit from Pelican, but it was larger than the Marchal causing the fan and shaft to protrude out from the housing, mis-aligning the belt.

Any help would be GREATLY appreciated. You can reply or post to my email below.

Thanks,

Brian F.
cmpd_patch@yahoo.com

This is same unit I have:

Marchal
 

For some reason, Pelican won't attach the photo I've uploaded.

The alternator is Marchal, marked 712.237.02 with a red half-moon back plate and four connectors, three marked "61" "D" and "B+". The regulator is a screw panel just above with a tab connector marked "D-".

I cannot tell which of the replacement units offered by Pelican would be a direct exchange.

Any help?

You should have a remote VR for that model year. Look beside the CDI box for a small metallic box with a 3 wire connector with brown blue and black wires. Was there a black wire by itself attached to the back of the alternator? If so, you have a remote VR.

Like Timmy says, your VR should be on the driver side of the engine compartment next to the CDI box with a three spade plug. If original, it is 40 years old. My Marchal VR finally bit the dust last year. Replaced with a HUCO. Works fine now. You can check if the connections are corroded by sliding the connector on and off a few times. Maybe that will restore function.

Thanks for the replies, gents. I will look first thing in the AM after the 100% humidity clears.

Where did you pick up the HUCO unit?

BF

This is the unit i have now:

http://forums.pelicanparts.com/uploa...1348359907.jpg

Definitely the remote VR alternator.
Huco or other brand wlectronic VR is available from Pelican.
Porsche 911 & Carrera Charging System - Page 1

Call Mark at stellar generator in Pittsburgh PA.

Before you get all hot and bothered about the regulator and alternator, pull the battery, charge overnight and with it disconnected check voltage. It should be in the 13v range with no load. 11.8 is low.
Could be you simply need a new battery.
-C

Thanks to everyone with the replies!

Pulled the battery (Interstate, about 15 months old) and put a fresh full charge on it.

You were right, I do have the remote VR (sheesh, see what you get when you pull covers) which is a large light grey box marked "SEV Marchal" and date coded 07/85. Amazing how it lasted 28 years!

It has a flat blade for the D+/61 connector and a screw mount post for the DF (black) connector.

The closest thing on Pelican (new) is the Valeo unit for the 70 amp Motorola (all mounts match).

I am inclined to drop the $60 or so to swap this first prior to pulling my alternator again.

Thoughts?

Oh, and thanks Driver_X for the referral to Stellar. I have a mechanic in Charlotte who doesn't trust any of the shops here any longer for rebuilds and is looking for someone who can handle that work.

I'll look him up.

You may try removing the noise suppressor next to the regulator. It may be faulty and causing a no-charge condition.

http://forums.pelicanparts.com/porsche-911-technical-forum/134720-pelican-parts-voltage-regulator-external-marchal-55w-alternator-911-1975-81-a.html

Can anyone provide a pic of what this noise suppressor looks like in the bay next to the VR?

Please and thanks!

The shape of the noise suppressor varies from year to year. Here is one from a 76. The black box to the left of the CDI box is the voltage regulator. Immediately below the voltage regulator is the noise suppressor. Here is a dusty photo:http://forums.pelicanparts.com/uploa...1376185933.jpg

I never charge a battery when its connected to the car, that way there is no possibility of cooking something other than the battery. I think the battery tender devices are low current, 2 Amps is getting up there.

Thanks. I am ordering the post/tab style VR from Pelican tomorrow to see if that works.

I'll look to see if the suppressor is still in place as well.

I appreciate everyone's help.

B

You know, I was re-reading you post, and if you were only getting 9.9 volts at the battery while running I'm inclined to agree with you that your alternator is toast. Typically, the VR is there to limit the charge being put out by the alternator. Typically, when VR's fail, the voltages will spike well above 14.5.

Check voltage at the battery at idle, and again at 3,000 rpm. Voltage @ 3,000 should be between 13 & 14.5v If they don't get that high, then you alternator is the culprit IMO. Mark @ Stellar can have it rebuilt in about a week, assuming he can still get the parts.....

Thanks, I will see about getting it out of the car and will call him Thursday. Should I go ahead and replace the VR as well? The only thing that Pelican has that matches the connections is the Valeo unit for a 70 amp motorola.

Would that still function properly with a 55 amp Valeo?

BF

That's this one:

http://www.pelicanparts.com/cgi-bin/...160390100-M262