Alternator warning light fix
06-10-2015, 12:11 AM
#1
Banned
Thread Starter
Alternator warning light fix
While the car is sitting in the garage waiting for a new AC freeze switch, I decided to pull the pod, adjust the potentiometer on the voltmeter and fix the non working alternator warning light.
My voltmeter always runs at least 1 volt low.
While I was at it, checked all the bulbs, cleaned all the connectors and checked the voltmeter resistor for 68 ohms. It was 69, so good enough.
The alternator warning bulb assembly was very much crudded over and wouldn't test with 9 volts applied unless you hit the bulb wires sticking up through the solder directly.
I guessed there was a break in the foil between the bulb and the terminal, so I cleaned up the old solder a bit and flowed new solder from the terminal back to the bulb.
The bulb tested good and tomorrow, hook the cluster up without the cover and pod and adjust the voltmeter POT.
Pulling the pod wasn't as much as a pain as I thought it would be and the instrument cluster foil was in much better shape than I thought possible for being 33 years old.
My voltmeter always runs at least 1 volt low.
While I was at it, checked all the bulbs, cleaned all the connectors and checked the voltmeter resistor for 68 ohms. It was 69, so good enough.
The alternator warning bulb assembly was very much crudded over and wouldn't test with 9 volts applied unless you hit the bulb wires sticking up through the solder directly.
I guessed there was a break in the foil between the bulb and the terminal, so I cleaned up the old solder a bit and flowed new solder from the terminal back to the bulb.
The bulb tested good and tomorrow, hook the cluster up without the cover and pod and adjust the voltmeter POT.
Pulling the pod wasn't as much as a pain as I thought it would be and the instrument cluster foil was in much better shape than I thought possible for being 33 years old.
06-11-2015, 12:49 PM
#2
Banned
Thread Starter
Now that I got the cluster back in after I scrubbed all the terminals clean, the voltage and the brightness of the lights have really increased. I also cleaned the body ground that is under the pod, missed that one last year.
Before I cleaned the cluster and adjusted the voltmeter, I was getting 13.4-13.5 volts at the jump post and at least 1.3 volts low on the voltmeter with a new 180 amp alternator. Now I'm getting 14.1 volts at the post but still not reading that high on the voltmeter.
The very crude all metal potentiometer on the top of my 82 voltmeter, not the plastic housed potentiometer shown in the tutorial on how to adjust the voltmeter, is maxed out and shows about 13.8 volts now.
Guess that is as good as it is going to get.
Before I cleaned the cluster and adjusted the voltmeter, I was getting 13.4-13.5 volts at the jump post and at least 1.3 volts low on the voltmeter with a new 180 amp alternator. Now I'm getting 14.1 volts at the post but still not reading that high on the voltmeter.
The very crude all metal potentiometer on the top of my 82 voltmeter, not the plastic housed potentiometer shown in the tutorial on how to adjust the voltmeter, is maxed out and shows about 13.8 volts now.
Guess that is as good as it is going to get.
06-15-2015, 02:08 AM
#3
Rennlist Member
I would recommend cleaning the CE panel, cleaning up the electrical connections in the pod, and cleaning the jump post, 14-pin connector and grounds before you decide the voltmeter is off.
Going through those steps brought my voltmeter within about 1% without having to adjust anything. YMMV of course but I am convinced that it is usually the sum of all of the bad connections between the voltmeter and the battery that accounts for most "inaccurate" voltmeters. You can check the meter itself with the pod out by simply connecting a known voltage directly to the back of the meter.
Going through those steps brought my voltmeter within about 1% without having to adjust anything. YMMV of course but I am convinced that it is usually the sum of all of the bad connections between the voltmeter and the battery that accounts for most "inaccurate" voltmeters. You can check the meter itself with the pod out by simply connecting a known voltage directly to the back of the meter.
06-15-2015, 08:53 AM
#4
Banned
Thread Starter
I did all all of those things prior to pulling the pod and the gauge did read at least 1 volt low with external 12 volts applied directly to the gauge.
After I cleaned all the connections on the pod and the body ground under the dash (which I had missed last year), the output of the alternator at the jump post went up from 13.5 to 14.0 volts.
The voltmeter on my 82 doesn't have the nice plastic potentiometer like shown in the tutorials, but a very crude and very cruddy all metal version.
After a thorough cleaning of the contacts, I took a jewelers screwdriver and adjusted the POT until the gauge showed 14 volts. I can't see how that would be wrong.
After I cleaned all the connections on the pod and the body ground under the dash (which I had missed last year), the output of the alternator at the jump post went up from 13.5 to 14.0 volts.
The voltmeter on my 82 doesn't have the nice plastic potentiometer like shown in the tutorials, but a very crude and very cruddy all metal version.
After a thorough cleaning of the contacts, I took a jewelers screwdriver and adjusted the POT until the gauge showed 14 volts. I can't see how that would be wrong.
06-15-2015, 04:34 PM
#5
Rennlist Member
I'm not trying to say that you did anything wrong. I wasn't aware that you had performed a direct check of the gauge when I posted.
Here is my reasoning behind performing the other maintenance items prior to adjusting the voltmeter: Suppose that there are 5 connections between the battery and the voltmeter(there are more but let's use 5) with a half-volt drop at each connection. Now suppose that you refresh two of those connections, then adjust the voltmeter to read battery voltage. Subsequent to this, you refresh the other three connections, perhaps while fixing something else. At that point your voltmeter will probably read 1.5 volts high. My comments were intended to help you avoid that situation, but it sounds like you're already there.
Now the only thing left to do is drive it like you stole it!
Here is my reasoning behind performing the other maintenance items prior to adjusting the voltmeter: Suppose that there are 5 connections between the battery and the voltmeter(there are more but let's use 5) with a half-volt drop at each connection. Now suppose that you refresh two of those connections, then adjust the voltmeter to read battery voltage. Subsequent to this, you refresh the other three connections, perhaps while fixing something else. At that point your voltmeter will probably read 1.5 volts high. My comments were intended to help you avoid that situation, but it sounds like you're already there.
Now the only thing left to do is drive it like you stole it!
06-15-2015, 05:41 PM
#6
Banned
Thread Starter
Sorry, didn't mean to sound accusatory.
I think I got all the grounds cleaned and I refreshed the CE panel a while back. But who knows how many phantom draws this car really has.
I'm a pilot by trade and live and die by gauges, of course they are digital displays not round gauges.
The inaccurate voltmeter has always bugged me. It still might not be accurate, but it is closer than it was and of course an "adjusted" gauge won't kill me like in an aircraft.
Thanks
I think I got all the grounds cleaned and I refreshed the CE panel a while back. But who knows how many phantom draws this car really has.
I'm a pilot by trade and live and die by gauges, of course they are digital displays not round gauges.
The inaccurate voltmeter has always bugged me. It still might not be accurate, but it is closer than it was and of course an "adjusted" gauge won't kill me like in an aircraft.
Thanks
06-15-2015, 06:18 PM
#7
Rennlist Member
No worries.
I agree, it's not super-critical, and I share your annoyance of having it read out an obviously wrong value. I have helped a lot of people resolve this problem over the years and have seen more than a couple run into the pitfall I outlined above.
Main thing is you're happy with it.
I agree, it's not super-critical, and I share your annoyance of having it read out an obviously wrong value. I have helped a lot of people resolve this problem over the years and have seen more than a couple run into the pitfall I outlined above.
Main thing is you're happy with it.