Alternator Light Bulb Location/Testing?

OK-944 · 03-13-2011, 02:45 PM

I still want to check my alternator light bulb on my 85.5 (does not come on during pre-ignition), and have the gage cluster out. I've removed the bulbs on the alternator side of the cluster and shined a light through the openings as suggested, but cannot get the alternator light symbol to light up this way. Is the alternator light bulb inside alt/oil pressure pod of the cluster itself? And if so....what's the best way to get at it and test it?

OK-944 · 03-14-2011, 04:51 AM

....Anybody?

kfray · kfray's Garage

On my 1987 944 NA the alternator warning light is a small red illuminated rectangle at the bottom of the volt meter scale. The bulb is part of the oil pressure / volt meter gage.

OK-944 · 03-14-2011, 06:15 AM

...so this means that I need to remove the oil pressure/alternator pod from the gage cluster, and remove the bulb from inside this pod?

kfray · kfray's Garage

I am not sure if the bulb is part of the gage or the circuit board in back of the gage, will you let us know?

OK-944 · 03-14-2011, 07:33 AM

Once again....anybody?

And any further hints about the best way to extract and test this bulb? Thanks!

kfray · kfray's Garage

Do you have the schematics for your car. Connector "C" or the right hand connector
(the connector behind the volt meter / oil gage) on the back of the cluster is the connector that connects to the alternator warning circuit. Pin 3 of this connector is connected one end of a 5 watt 68 ohm resistor and one side of the alternator warning indicator. Pin 4 is connected to the other side of the resistor and the other side of the alternator warning indicator. 12 Vdc is supplied from the ignition switch to pin 3 of the connector this 12 Vcd passes through the resistor and bulb and is connected to the D+ connection on the alternator. If the alternator is not outputting the warning light will illuminate.
Try this link to see how the indicator is mounted:
http://www.*****************.com/Instrument_Panel_Bulb_p/pp999.631.301.90.htm

OK-944 · 03-14-2011, 11:58 AM

Thanks Kfray! Good reference to Paragon also...which shows the actual bulb locations - exactly what I needed!

My alternator light is not coming on at all...plus the voltage indicator does not read while the engine is running.

So I still have not quite gotten to the bottom of this...but at least maybe I can remove the alt/oil pressure pod from the gage cluster and check the bulb itself. I'll do this and check back here soon.

89-944NA · 89-944NA's Garage

No need to remove the gauge from the cluster, lights attach on the back, and twist off. Shine your light from the FRONT (throough the face) of the gauge.

kfray · kfray's Garage

What does the volt meter read with the key on. It should read the battery voltage, also check fuse #18

OK-944 · 03-14-2011, 12:48 PM

Just got the Alternator bulb out...to do this I had to first remove the inner Alt/Oil Pressure Pod (very easy...remove nine screws in back of gage cluster, gently pull apart, then remove two "footballs" which secure Alt/Oil pod, then remove pod, then remove bulb).

The Alternator Bulb looks good - but perhaps I'll check the in line resistor also before I put the gage cluster back into the car.

kfray · kfray's Garage

Quote:

Originally Posted by OK-944

Just got the Alternator bulb out...to do this I had to first remove the inner Alt/Oil Pressure Pod (very easy...remove nine screws in back of gage cluster, gently pull apart, then remove two "footballs" which secure Alt/Oil pod, then remove pod, then remove bulb).

The Alternator Bulb looks good - but perhaps I'll check the in line resistor also before I put the gage cluster back into the car.

Check the resistance of connector pin 3 and pin 4 to the alternator warning bulb socket, it should be near zero ohms resistance.

OK-944 · 03-16-2011, 06:16 AM

Alt. bulb works! I took the alt/oil pressure pod out, cleaned as many contacts as possible, and tested for continuity. Also tested the resistor which checks out fine. I also found that the three big gage light bulbs to lacked continuity...until I cleaned up those contacts also. I then cleaned the "football" contacts plus whatever else I could (plus checked the odometer gearing), before re assembling and re installing everything back into my car.

When I turn on the key the alt bulb works....but I have not started this car since mid November, so I want to add a bit of fresh gas plus maybe turn the crank by hand a few times first.

I think a big lesson with these old cars is that the electric stuff can cause huge and sometimes difficult to trace problems (yeah, I know I'm preaching to the choir!)...and its definitely worthwhile to take a bit of extra time to undo connections and clean them as thoroughly as possible.

To be honest, there have been times (especially after removing the entire dash assembly) when I've been so tempted to just grab a bundle of wires and rip everything out and start over with completely new wiring. But what a project that would be! Has anybody actually done this?

John_AZ · 03-16-2011, 06:34 AM

I know this is late but may help others with contacts behind the dash guages:

From the "tech info center" above^. Many other articles as well.

Pelican Technical Article: Solving Strange 944 Gauge Problems...

John