[Dekuiper]

1981 Spider.

Driving down the freeway with heater fan on (first time it worked) and take an exit. Stop, turn right, come to a traffic light. Hear a "snap", alternator light comes one, tach drops to zero, all gauges read low. Drive 1 mile to destination and check belt. Everything looks OK.

Play a game of soccer, tell teammates to follow me home, start Alfa, no alternator light - for 4 seconds.

Drive home 35 miles with headlights on. Alternator light on, oil pressure, temp, and fuel gauge all low to 0. But I make it. Wow. What a relief to be home.

Did I blow a fuse? Could running the heater fan have done this? I find it interesting that the tach quit at the same moment that the alternator light came on.

Tomorrow I'll check fuses but thought I'd post here while having a beer.

 

[Tifosi]

Any reason to think the tach drive cable broke loose (81 is mechanical in'it?) and whacked the regulator or junction block?
(yeah, I know, looong reach)

 

[Dekuiper]

No idea. Where is the regulator or junction block? Oh - and occasionally the tach would jump and show some sign of life at least for a split second...

 

[papajam]

The snap you heard was the sound of fuse #6 blowing.

 

[Dekuiper]

Ding Ding Ding...Papajam wins!

Fuse #6 (8 A) is blown. It just figures that is the one I don't have in my collection so off to the auto parts store I go.

 

[Tifosi]

Wasn't even a competition I was just hoping for a good guess while papajam simply flat out knows

The thing to investigate now is why did the fuse blow.

 

[Dekuiper]

But wait. There's more

I replaced fuse #6 which is for the heater fan and a list of other items. This makes sense because it was the first time running the heater fan and it is still not spinning real well but this did not improve on the tach or the alternator light.

I noticed that fuse #4 is also blown. The manual says this is for the radio. That wasn't even on. So a new 8 A fuse there too.

There is still no tach and the alternator light is still on. Also, the battery doesn't need a charge - even after 40 minutes of driving like this with the headlights and all on so I assume the alternator is actually working. The Tach and all gauges work occasionally and while they are working, the Alt light is off. They alternate. If the alternator light is on, then the gauges including the tach don't work.

I have to believe then that the tach is not mechanical. Sorry Mr. Tifosi.

Could I have a short somewhere that would cause this?

Just for giggles, I traced the red wire from the alt to a spot on the fender where there are 2 other red wires. (It seems this wire is mentioned a lot if searching the forum for alternator light issues.) I disconnected the battery and then removed and cleaned these connections. No improvement.

Other thoughts?

 

[papajam]

The fuse contacts in the fusebox are dirty. A pencil eraser works well to clean them. While in there, also bend each fuses contacts together a little bit so as to provide a tighter mechanical connection on the fuse.

 

[Dekuiper]

Correct Again! Wierd but totally correct.