I went to Advance Auto and had them check the alternator. The man ran the test two times and said the alternator is starting to fail. However, when I compare his results to what is in my Datsun 240Z, 260Z, 280Z, 1970-1978 Automotive Repair Manual, it does not look like it is failing.

 

The print out shows that the charging system voltage on test one is 12.81V. On the second test it is 12.97V. The man at Advance said it should be at 14V or so. However, in the Repair Manual it says the following:

"If it registers over 12.5 volts then the alternator is in good condition, it if registers below 12.5 volts then the alternator is faulty and must be removed and repaired."

 

Since both tests were over 12.5 volts, then according to the manual, the alternator is good.

 

What say you?

Perhaps I am reading the printed results wrong! The Starter Test reads "Cranking Normal" on both tests. However, the Charging System Test reads, "Results - No Voltage". Despite saying this, it show No Load: 12.81V, Load: 12.81V. If there is "No Voltage" does this mean the car is running off the battery?

 

Sorry for my ignorance on these things.

Mine all show 14 volts at the battery when idling.  It seems like I've bought them from Advance online with a coupon code for $20, then pick up in store, they keep them on hand.  reatailmenot.com has some good codes for Advance. 

I suppose I disagree with the FSM, which is a first!  (Does it really say 12.5V?)  Your alternator voltage should be AT LEAST 13V, perhaps at least 13.5V, and usually 14 - 14.5V.  An alternator putting out 12.8V can keep the system going, I suppose, but it's going to be really slow recharging the battery and will leave the battery less than fully charged in practice.

I think he's going by a Haynes Manual?

It was a Haynes manual.

 

Someone else said this to me about the alternator:

 

"I just recalled that there's one more possibility, common to the Z's - output at idle tends to be low.  So, depending on what the machine measures, it may have seen no voltage because the the measurement was made at idle speed.  Today's cars have ECU's that bump up the idle RPM to make sure the battery stays fully charged, and the testing machines are designed for them.  Our old Z cars don't have that feature.  One more reason to get a meter and check for yourself.  It's not that hard to do."

 

Thoughts?

In any case, I am going out to get a voltmeter and delve into learning things electrical.

" I am going out to get a voltmeter and delve into learning things electrical"

 

Let me be the first to welcome you to the dark side.

 

We have cookies.

COOOKIEEEEEEESSSS!

Nom! Nom! Nom! Nom!

 

Alright! My first venture into the dark side! And it was not bad at all!

 

Used a voltmeter and it shows the following when connected to the battery terminals:

 

Car off: 12.8 volts

Car at idle: 12.8 volts

Car under load: 14.8 volts (sometimes getting up to 14.9)

 

"Car under load" is the lights on, fan on high, and engine revving up to between 2000-3000 RPMs. As I release the gas pedal and the RPMs drop, the volt meter's reading drops. So, it looks to me like the alternator is doing it job.

Alright! Back onto the electrical issue with limited time this week.

 

I took the back panel off (the plastic cover you need to remove to gain access to the back lights and all the wires there). I checked all the wires, the ground, the connectors and bulbs. Everything looks good. So, now it's on to other things.

 

As a reminder, the following is NOT working on the dash:

 

- Turn signals and hazards (neither are they working externally on the car)

- The oil pressure gauge

- The volt meter

- The clock (though I don't think that was working before the dash lights went out)

 

The following is what is working on the dash:

 

- The speedometer (of course)

- The tachometer

- The temp gauge

- The fuel gauge (though the float in the tank gets stuck at 1/3 tank even on full)

 

Other things work like:

 

- The fan for the vent

- The center dash light (the one you flip down to turn on)

- The fasten seat belt light and buzzer

- The bright, red brake light at the bottom of the speedometer (in fact, for some reason this is on continuously)

 

I don't know if any of this information helps to pinpoint what could be the issue, but I thought I would post what I know so far. Again, I am learning about electrical, so any help would be appreciated.

For the brake warning light on all the time... look at the wiring for the parking brake switch, passenger side of the tunnel, near the parking brake lever.

See if it has become disconnected.  This is what turns the brake light off when the brake lever is released.