No charging

[aston@ultrasw.c]

I have a 95 993 3.6 transplanted into an 86.

A couple of weeks ago I noticed that after starting, the volt meter remained at 11 V and took a few minutes before it jumped up to 14V.

Charging light behaved normally: on with ignition (nice and bright), out as soon as engine starts.

Tired voltage reg I thought. So I purchased a Bosch rebuilt alternator to last another 20 years.

Installed same.

No improvement GAAAAA.

DMM agrees: 11.9 V off, 11.5 V engine running. (Crappy DMM btw)

Charging light normal. Quick road test and no voltage jump! 11.5 V the whole time.

Today I checked wiring: engine ground nice and clean. 14 pin connector (blue wire) clean up and spread pins a bit.

Still no charging?

What next?

[wwest]

Normal start, crank?

Defective DMM, or poor measuring point...

Possibly a shorted battery cell. Normal charging voltage ~13.50V minus cell value, 2.15V, = 11.35V.

[aston@ultrasw.c]

Thanks for the info.

I got some better data.

Battery was charged overnight.

At rest 12.55V, engine running 11.98V

As a control I measured the Tundra

Rest 12.64, engine running 13.54

This suggests my DMM can be believed.

Measurements are taken directly from battery terminals.

Engine cranks and starts normally.

[timmy2]

Alternator charges battery through the connection at the starter.
Check to ensure it is tight and clean. Disconnect negative at battery when doing so.

[aston@ultrasw.c]

Originally Posted by timmy2

Alternator charges battery through the connection at the starter.
Check to ensure it is tight and clean. Disconnect negative at battery when doing so.

Power connections at the starter are clean and tight.

However, the yellow start wire was about ready to fall off. I re-terminated and it's all tight now.

[Bob Kontak]

Originally Posted by aston@ultrasw.c

However, the yellow start wire was about ready to fall off. I re-terminated and it's all tight now.

Yellow wire on the starter? Good find.

All ok?

[pampadori]

Ground from motor to chassis. Add a temporary ground in the form of a jumper cable from metal on engine to metal on chassis and check voltage at battery again. If it improves, replace ground strap.

[aston@ultrasw.c]

Originally Posted by Bob Kontak

Yellow wire on the starter? Good find.

All ok?

Yellow wire sends power to the solenoid, unrelated to charging prob.

Just aggravation avoidance.

Charging is still FUBAR.

I will try temp ground cable

[wwest]

try the tundra battery in the 911 and vice versa.

My bet is now more solidly on shorted battery cell.

Build up of plate metallic debris in the bottom of the battery, (intermittently) shorting cell(s) is very common failure mode.

[Bob Kontak]

Originally Posted by wwest

My bet is now more solidly on shorted battery cell.

I am not going there yet.

My bet is that the install of the alternator may be wrong. I don't know why the charge light would not be on. However, always go to the last place you put a wrench on the car.

First post initially, volts were low but then took a while to get up to normal. After alternator install, volts were low all the time. There was no improvement but there was major change in that the charge voltage is not making it to the battery.

[grizzfan]

Just curious, why has no one mentioned the Voltage Regulator?

Tom

[Bob Kontak]

Originally Posted by grizzfan

Just curious, why has no one mentioned the Voltage Regulator?

Tom

OP mentioned VR in first post. Was basis for changing to another alternator.

[aston@ultrasw.c]

'kin hell!!!

So I opened up the back of the alt to check my wiring, wouldn't have been the first time I screwed something up. Nope everything is in the right place. I even cleaned up the ground ring lug for good measure.

Still no charge.

Then I pulled the (almost new) battery out of the tundra and hooked it up with jumper cables. Porsche battery out of the circuit.

engine off 12.66V

engine on 12.33V

let it warm up for a couple of minutes, revved the engine a bit - no change!

Bastard!

[aston@ultrasw.c]

I just connected the engine block to the battery ground with a jumper cable.

No change/No charge.

[wwest]

What is the 12 volt level in the engine compartment....?

Engine off, key off.

Engine off, key on.

Engine running, idle

2000 RPM?

[Bob Kontak]

Originally Posted by wwest

What is the 12 volt level in the engine compartment....?

Engine off, key off.

Engine off, key on.

Engine running, idle

2000 RPM?

I think you can pick this up at the 14 pin connector without pulling alternator back.
Not sure which pin.

[wwest]

One of the 3 fuses in the engine compartment has unswitched power.

Or maybe all three....

[aston@ultrasw.c]

So I *may* have fixed it.

I took a wire and connected the blue wire, from the engine side of the 14 pin connector, to the blue/red side of the battery indicator on the dash.

It worked: engine fired up and voltage gauge was immediately up around 13.5+

There is little doubt that it was a self-inflicted wound, it's just a matter of which weapon was involved.

Some of the wires were a little crispy from a welding project. Then there was the wiring clean up that I did a few weeks ago, and the race I did in the pouring rain 2 weeks ago.

Thanks for everyone's help.