951pcarguy

The battery on my 87 951 is not holding a charge, even though the battery is < 2 years old and registers 620 CCA after trickle charging. After 30 min of driving I'm down to the bottom of the Volt guage on the dash, and everything goes haywire.

Charging back up overnight will yield similar results. Is this as easy as a new alternator or might it be something else?

Jay

PaulD_944S2

Definitely appears that you alternator is not charging your battery. Check the battery voltage before starting (leave the battery connected), should be about 12.5 volts for a fully charged battery, after starting the voltage should rise to about 13.5 volts, IF the alternator is charging.

Depending on miles the age of your car, the brushes in the regulator may be worn out in the alternator. You can replace the regulator for about $25-50, or solder in new brushes.

joejoe

Is there a low charge light on the cluster? If it does not light with key in 'on' position you need to replace it as it is part of the charging circuit. (you need to remove cluster for this)

jeffro951

Yes do this and check the battery for dead cells and/or sulfation.

The nissan Quest alternator is an awesome upgrade should you decide to replace your alternator.

Angus Shaw

Paul, just replaced the starter and battery on the 944NA after several rounds with dead batteries. Starts and runs great but did not see the battery gauge go above the 12.6 at start even after a small drive. Would that be symptomatic of a failing alternator down the road?

PaulD_944S2

Angus Shaw="Would that be symptomatic of a failing alternator down the road?"
No, most likely poor connections where wires are crimped in lugs, or bolt to body, firewall, or engine.

951pcarguy="After 30 min of driving I'm down to the bottom of the Volt gauge on the dash, and everything goes haywire."
When the brushes on the alternator regulator go bad, the voltmeter will drop several volts as the battery discharges. Ultimately the engine/vehicle will stop running when the battery can't keep the fuel pump and electronics running. This is a bad alternator.

If the battery voltage rises to about 13-13.6 volts at the battery terminals then the alternator is charging the battery. If any of the cables are resistive, i.e. corroded (and may not be obvious) then the voltage may be less.

You can check at the positive post on the alternator to see if the voltage is higher there than at the battery when the engine is running. Best way is too attach a small insulated wire and connect that to your meter to read the alternator positive; it's too crowded to do it differently.

951pcarguy

Thanks for the advice Paul - even after a trickle charge for 2 days, I never saw over 12.9 volts at the battery. The battery is about 2 years old, and I had it checked where I bought it and it's still OK, as it delivered 720CCA after a 30 minute quick charge.

I'll check the positive post on the alternator next.

jeffro951

That would be a sign of a failed alternator now. take a voltage reading at the battery with the car running, if you have 12.6 volts you have a problem if you have 13.5 to 14.75 your alternator is working and your gauge is suspect faulty or wiring to it. if you have higher voltage than 14.75 at the battery then you will be cooking your battery real quick! can you say sulfur smell?

PaulStewart

+10

The alternator will not start charging if this bulb is burned out.

jeffro951

Its an 87 so it has the gauge and the central warning system, no separate bulb for the charging system. that would be true in an early car.

951pcarguy

Thanks Jeff, just sent the Nissan alternator guy on eBay a message asking for a 944 Turbo alternator upgrade package.

jeffro951

Sure anytime, I will post a link to the places I have gotten shorter belts too along with the size that I have used.

Angus Shaw

Great weekend to work on the car so we will run this test and hopefully it is just faulty wiring!