Charging question on a 914-6 Options

[db9146]

Well, I have made a temporary conversion of my -6, inserting a rebuilt 2.7S with ITBs, MS3, and distributorless ignition in place of the tired 2.0L. Before putting the engine in, I decided it best to install a new alternator along with a new engine/alternator wiring harness.

The alternator is for a 1965-1977 911 2.0-2.7 that uses an external VR.


and here's the new wiring including a new ground strap to the engine case.


The large red cable goes to the starter, the smaller red wire is D+, the black is DF, and brown is D-.

I thought the problem might be the battery because of its age but when I checked the output of the charging system at the battery, there was none. I replaced some of the dash lights with LEDs but made sure not to replace the GEN warning light, which is not coming on despite the alternator not charging.

Should I next pull the D+, DF, and D- plug and check for alternator output across DF and D+ momentarily?

If there is output, what then?

If not, what's next?

[db9146]

Well, I spent last week dropping the engine and addressing several items I had noticed, including pulling the alternator and having it checked. The local auto electrical shop put it on his bench tester, spun it up and said "so its 55 amp unit, huh?" so it checked out okay. I double checked the wiring, fan belt, etc. as it was going back in.

Everything seems to be the same as it was before I pulled the engine. All the connections are good, dash light working as it should, traced the 12v through the circuits following the info posted (thanks again, LarryM), and swapped to a different VR. Getting 13.1 to 13.2V at the battery with it running. Not really any different before dropping the engine other than knowing that the alternator is working and the connections are good (even pulled the grommet out from around the large cable to the starter/battery from the shroud enough that I could check the back of the alternator once it was back in the engine....once I remembered I had a tiny camera to check it with....doh).




I also managed to seal a small oil leak, a small exhaust leak, clean up the underside of the car a little more, and install a new muffler so I guess it wasn't all for naught. I just really wish I could get the charging voltage up a bit. I may try a variable VR and see if that has any effect.

You know, thinking about the VR, the external VR for a 911S looks like this:


I wonder if even though the wiring is the same, there is some difference in the settings within the VR that is causing the output to be so low. The whole time I had the original engine in the car, I never checked the charging voltage. The original 2.0L -6 is a 911T engine I understand so you would think that the stock -6 VR would work fine with any other 911 engine with an external regulator, right?

[larryM]

I wonder if even though the wiring is the same, there is some difference in the settings within the VR that is causing the output to be so low. ........... you would think that the stock -6 VR would work fine with any other 911 engine with an external regulator, right?

all the same - - all regulators are "variable" - they deliver to load demand
Part Number: 901.603.206.01
Brand: Bosch
Model: 911, 912E, 914
Year: 1965-1976

your post #5 above said ... "It was 12.8V. I turned the key (GEN light came on), then started it up (rev'ed it and GEN light went off) and measured the voltage at the battery again - no change."

therefore you have improved something, since you are now getting 13.2 which is in the "normal range" vs the 12.8 previous readings


13.2 V at what rpm?

and with what loads being drawn?

turn on everything electric, run 2000+ rpm, & see if it kicks up higher volts - it should

BUT- if the volts drop lower than 13.2 via that simple test, it ain't chargin' right