Electrical Mayhem....

[Blue Beard]

Okay, so a while back I posted about my gas gauge reading half full. Got some good tips, unfortunately none that solved the problem. The problem has grown. Here is what I have going on:

1) the gas, oil, and temp gauges all read about half of what they should
2) the amp gauge stays steady in the middle, but often starts jumping around to the left for no clear apparent reason. I mean wildly jumping. Then stopping for a short time, etc, etc.
3) at night my lights dim down and then brighten up as I drive down the road. It's like I am the lighting crew in a disco.

Here is what I have done. Grounded the battery to the frame. I think it May fixed the lights, but I have not driven at night yet so cannot be sure.

Pulled the voltage regulator to try and adjust that. I was told if it was working it at all it worked and that it just needed to be adjusted. Nope, I was able to adjust it down, but not any further up. That would be as in the screw would turn, but they never went past where they were before.

So I am guessing this leaves me with either the voltage regulator is bad. Replace and be on my way. Or it has nothing to do with this and there is something else keeping the guage from going past half of what would be normal.

Any ideas on what could be causing this. I have looked for a bad ground, but not found one. Do you think I just missed one? Maybe the voltage reg? Bad alternator????

Any help would be appreciated.

 

[RobertC]

Based on what you state you have multiple (or two) problems...

Have you tested the battery to see that it has a full charge?

You state you adjusted the voltage regulator???

Afaik, the voltage regulator on a 73 is an internal voltage regulator that is part of the 10si altenator (and is not "adjustable" from what I saw).

Has a po (or you) modified the electrical system to "add" an external voltage regulator?

I forgot to ask an important question..

Has the electrical system been "reworked" ("hacked"?) wires replaced / spliced? If so, my simplified solution will probably not work -- though you could get your altenator tested... You will need to check all the "replaced" wires to see that they are correct (against a wiring diagram). Also, check the connection in the bulkhead connector -- a known problem area -- especially in scouts.

Gauges -- your problem might be related to loose connections at the gauges. Disconnect the battery before you touch the gauges...

#2 -- have not seen this

#3 -- had this problem on my t/a -- though the ammeter fluctuated on the charge side -- not the discharge side as you indicate in #2

in my case, the place I took my t/a stated that the altenator had a bad diode and it was replaced with a re-manned 10si altenator. ( I just took the "dead" 10si altenator apart to "rebuild" it ("years" later) and I do not recall seeing any "adjustability" with the internal voltage regulator "piece" (like you have on an external voltage regulator). )

problem (mine) is that I tested the removed diode (from the "rebuilt" altenator referenced above) and it tests "good"... But, I am an electrical testing idiot...

not the best answer, but -- replace the 10si altenator with a re-manned one (if your electrical system does not have an external voltage regulator...) -- and, see how many problems you have left.

Actually, my understanding is that chain stores like autozone can test your existing altenator -- you probably should have your exiting one tested before replaceing it.

 

[Michael Mayben]

We need to know what alternator is mounted now, if it has an externally-mounted regulator, it is not a delcotron "10si" which is an internal/solid state regulator system. Those came into production sometime in calendar year '71 and were phased in over time so that date is not an absolute.

Ya don't take an external regulator off or out of the system to adjust, it must be adjusted with the system actually operating and using a voltmeter and an ammeter.

If this is an aftermarket "add-on" voltage regulator then all bets are off, that is not an oem item.

But no matter, what you describe is a classic "failing alternator" though a loose drive belt can cause similar condition. Also since the drive pulley on a delcotron is not keyed in place, the pulley can be slipping on the shaft if the nut is loose.

Remanned alternators are too cheap (varying quality/price points) to spend much time in scruuin' with 'em. And diagnosing charging system problems with the unit mounted on the vehicle must include a servicable/fully charged battery to start with.

If you don't know which alternator you are working with, post a pic and we'll make an id.

 

[Eric VanBuren]

The jumping ammeter and lights that go bright and dim are most likely caused by a poor connection on the wire from the alternator to the ammeter, most likely at the bhc. Does the bright and dim lights correspond to the ammeter jumping? Try cleaning and tightening those pins and see if that makes it better. If the lights still flash another way to determine if the bhc is the problem is to run a jumper wire from the alternator b+ terminal to the battery + side and see if that cures the lights. That does by-pass the ammeter but you will likely still see it jump around because the current coming into the cab can change paths as the connection comes and goes.

For the gauges what have you tested and done so far, other than trying to adjust their regulator? Have you checked the resistance of the wires to the sender from the gauge and inspected/cleaned/tightened the connections?

You can verify the calibration of the gauge system with some 10 and 33 ohm resistors. With a 10 ohm resistor between a good ground and the sender wire, the gauge should read at the top line, f h or h. With 4 x 10 ohm and 1 x 33 ohm connected in series the gauge should read at the bottom line c, l or e. +/- 1 needle width is considered within calibration. You can also do the test directly at the stud on the back of the gauge, If you are very careful to not short out the ammeter connections when working on the ammeter/fuel pod, To eliminate error caused by resistance of the wiring to the senders. If all the gauges read similarly low then almost certainly the cvr is cluprit. If their readings vary a lot then it could be a combination of poor gauges, failing cvr and system resistance when checking at the sender connection.

In many rigs where the harness comes out of the frame at the back there is a single bullet disconnect near where the wire heads over the frame going to the tank so dropping the tank isn't necessary to check the bulk of circuit for the fuel gauge.