The battery is about 18 months old. I think I will get a new battery and see if that's it. I still would like to learn how to check the voltage coming out of the alternator. Anyone?

I think a new batt is a good idea because when you do that to a battery it isn't the same anymore.
Alt output is measured with the car running and alt charging, put a volt meter across the battery terminals. First measure the voltage not running (batt voltage) then start the car and then measure again. I think it sould be around 14.7 if the battery is fully charged but I am not sure

OK a long shot, but what if the Ignition switch is intermittently bad? Couldn't this cause intermittent cut out as well and intermittent charging problems?

i worked on an Alfa once that had a strange no-start situation. It would start about every 5th time the key was turned - otherwise it would just crank.

After searching for a while I found that there was an audible click inside the fuel injection computer (right when the key was turned) everytime it would start - no click the times that it just cranked without starting.

Turned out to be a bad battery.

Electronics are different than electrics. You may have 12.0V with a million amps available - it will spin a starter forever but a solid-state switch that needs 12.1V will never move. I think you will spin the starter just fine (but slower) on 10 or less volts if you have enough current available.

I say replace the battery, as it is probably injured and should be replaced anyway, even if you do have another problem (go for the low hanging fruit).

Keith,

I don't think it is the ignition switch because that happened last year and I replaced it. From that point I have not put heavy keys into the switch. Also, since that has happened previously, I can tell you that the cut off is not the same. When the ignition switch went out it would not even turn on the fuel pump. It was intermitent like you described but it was alive or dead. Good guess!

I have been working an have not purchased a new battery yet. I will find out soon enough. See Ya, Mark

I would like to ask several questions about this problem since it looks to me to be only an electrical problem. I have had this type of problem in my 80SC Targa. I diagnosed it down to an intermittent connection at the fuse block for the ignition system. Car ran fine until the poor connection got hot causing increased resistance and failure of the ignition system and the engine dropping dead at speed. Once everything cooled down it would start up again. I striped back the wire and cleaned the connection. problem resolved.

When the car will not start have you tried checking the igniton spark with a timing light?.
If no spark then your on the right track. I would suggest checking the wiring at the fuse box for any discoloration or heat damage at the terminal. Also check to make sure the connection is tight.

You mentioned at low RPM a dim alternator light when you increase idle the light goes out. I had that problem when I first purchased my car in 91 (Third owner). The alternator has three sets of diode banks plus three exciter diodes. My exciter diodes where deteriorated from heat damage causing poor feedback control to the voltage regulator. I replaced them with three 1N4000 common diodes for about $1.00 and resolved that problem. The alternator is still running strong today. I hope this helps and good luck with the problem.

Targa80

Smart money's on the battery, but there's something else going on too. No way a modern battery, that's only 18 months old, should be out of water. May have charging problem too (ie regulator) that over charged the battery, boiled off the water and fried a cell. Be sure and check the charging system too if you replace the battery or you may be going through this same thing in another couple of months.

Mark,

To adress the 'Zero-Ampere Speed' issue, and decrease that speed ... I recommend adding a 5 Watt resistor in parallel with your alternator warning bulb ... just as is recommended in the integrated-regulator alternator upgrade bulletin. According to the <b><i>Bosch Automotive Handbook,</b></i> 4th ed. p. 810 ... this resistance value controls the so-called '0-Ampere speed' of the alternator, and you can use a 68 Ohm resistor to give the best alternator performance at idle speeds ... so that is what I would recommend -- a 68 Ohm resistor!

Early S Man was right again!
 

I took my car in for a major service. While I was talking to the mechanic I asked him to check the regulator after I had explained this problem. Long story short, the regulator was shot. The alternator was putting out 20 amps!

No wonder my water was boiled off. Any way it runs like a champ now. He did say it wouldn't be long until I would need a re-build. Given the 150K on this re-build, he guessed that the PO (and he was right) had done a simple re-ring and did not replace pistons and cylinders.

After reading about the Euro Carreras I'm thinking the re-build should go euro specs. Anyone got opinions?

Mark,

You mean 20 Volts, right?

Definitely, RS 2.7 P & C ... and 'S' cams ... 200 hp at 6300 rpm! You won't regret it! Redlined at 7300 rpm!

Yes Warren I did mean to say volts! Can you see now how Intro to Electricity gave me fits? Thanks again for the help.