Question: "low voltage at idle" deal

Been reading a lot about this lately, there are several well known remedies.

My question is, does low voltage also keep the turn signal and hazard flashers from working properly ?

1979 D-150. I cannot figure out why the turn signals are so intermittant.

Related question: What do folks use to clean the contacts at plug-in points, male and female plug-ins ?

Might act slower, but not intermittent.



Deoxit

Cleaning will reduce voltage drops due to resistance.
Lower voltage at idle is generally not a resistance issue. Its a lack of power generation at idle rpms. Resistance to current feeding the rotor (and in the return) can contribute to this, but if its really low then its worth troubleshooting.
If its resistance, that will show as voltage drops in the circuit current is flowing in.
If its at the alternator, do a full field check to see if its the alt or the VR.
If its the alt, then check for blown diode(s) or one of the windings is open or shorted. Lose any one of the 3 stator or rotor windings, or the rectified output from same, and power production will drop accordingly.

Resistance in the turn signal circuit would reduce the current through the flasher unit, slowing down. I agree with Sniper.
In the '79 truck wiring diagrams Krautrock posted the other day, IIRC it looked like the turn and hazzard flashers were in the fusebox.

Other connectors that can sometimes be problematic are the ones for the steering column. Depends on specific conditions.

i rewired the alt output on my truck, (it's a 77 but i had the '79 wiring diagram), the bulkhead was bad, the connection going into it and feeding the electronics inside and the ammeter had alot of resistance.
after rewiring, the turn signals did flash alot more consistent, also brighter and faster.
wipers also work alot better, even at idle...

i found this after i had rewired it, it's similar to what i did.
https://ramchargercentral.com/electrical/ammeter-bypassbulkhead-fix/

The problem with that write up, and all the others like it, is that its based on a fundemental misunderstanding about power.

The 'full alternator power' NEVER flows through the ammeter.
Power flows from the highest voltage source (usually the alternator) to the equipment, be it ignition, headlights, or whatever.
The only alternator power through the ammeter is power needed for recharging.

The problems occur when the battery is run down a lot, then needs massive recharging; and more so when other stuff is attached to the battery side. Stuff like winches.
It did not help that the ammeters on a several years of those trucks were in plastic housings. Running 40 ampos or more through those circuits was bound to heat stuff up. Then the pressed studs got loose.

But that doesn't change the fact that I began with. On a truck with no added accessories, power from the alternator does not flow through the ammeter, except what is needed to recharge the battery.

Note: The above schematics show a points ignition and pre-1970 positive controlling voltage regulator.
Power distribution concept is the same as what you have.

Thanks Mattax !

I've been studying the heck out of the 1979 electrical schematics. When I first posted, I wasn't sure if the
plug-in flasher units were voltage sensitive, the hazard and the turn signal units.

But now I have additional uncertainty about how the parking lights and the turn/hazard light system even works.
I can't make sense of the circuits, the current flow. The schematic does not show the bulbs to be grounded,
so where is the end of the circuit ?

I don't have the full schematics - just the pages 2 through 5 that Krautrock posted in another thread.
My guess is yes they are grounded. Maybe the socket is in direct contact with metal housing?

As far as voltage sensitivity - indirectly yes they are.
The flasher units have a metal or bi-metal strip the current flow through. The current heats up the strip, and it bends or snaps away from the contact breaking the circuit until it cools again.
Current drawn by any bulb is voltage dependent.
Lets take an 1157 bulb's brighter filment as an example.
It's rated to draw 2.1 amps at 12.8 Volts.
When provided power at high voltage, say 14.5 Volts, it will draw more current. It will also burn hotter and brighter.
Yes - Give it too much voltage and it will burn itself out kindof like a fuse.

The catch is that the bulbs must see that higher voltage to draw more current.
Even when the alternator is producing power at 14.5 Volts, resistance in the connections leading to the turn signal circuit will reduce the voltage to some extent.

I'll look at the diagrams I do have and see if it the turn signal and parking light circuits look similar to the set up in my '67 Barracuda or '85 Grand? Wagoneer

The scheme looks similar to my '67.

On the '79 diagram, the upper half of the fusebox consists of circuits that only get power when the keyswitch position is in run or accessory.
I can not make out exactly which feed connects to the turn signal.
It is probably one of the 'Accessory' feed wires, Q1A or Q2.

The lower half of the fuse box is always hot. The hazzard flasher gets a dedicated wire direct from the battery (F38). Older cars (and prob trucks) just use a shared buss bar in the fusebox.

When the turn signal switch is flipped up, current can flow through the flasher down the switch feed (F38) to the front and rear lamps. If its a right turn signal, that's the light green and dark green wires.

For brake lights, I read the the diagram as power to the white wire S17. This goes through the hazzard switch as long as it is in OFF position. From the hazzard switch it feeds the rear lamps regardless of whether the turn signal is blinking one of the. But it might be like my '67 and where it only feeds the one not blinking.
This is how Chrysler illustrated the turn switch in a 1968 Master tech booklet.
I've colorized the switch's brass contact surfaces.

Parking lights.
Its hard to tell from the diagram - I think there's a connection missing or other small error.
They may share the same fuse as the stop lights.
But the stop lights get power from wire F38, and the parking lights get power from F37. At least that's what it looks like to me.
F37 should connect to the second power feed terminal on the headlight. When the switch is pulled out, power to the lights goes through green, tan and or yellow wires.

I disassemble each connector from the harness one at a time, by pushing in on the locking barbs with a jewelers screwdriver, and once out I use a dremel with a wire brush attachment to scrub them clean.Then I bend the locking barbs back into position, use some dielectric grease on the connector and snap it back into place in it's respective place in the harness.

Sixpak,
I guess I just have to agree that there is no shortcut for being meticulous.

Mattax, I looked closer at the bulb sockets, 1157's HAVE TO be grounded.
Also, after I put in the direct alternator - to - battery line, I have about 14.5 volts at normal idle, all around the hot circuit.

Only thing I don't have now is hazard flashers, even though I have 14 volts at the flasher hot side. I've been meaning to replace
the turn signal switch assembly anyway. I don't want to take apart the steering wheel stuff until I have replacement parts in hand.
I'm guessing the hazard switch is part of that.

It is looking better !

Hemienvy, where in Washington might you be? I am fair at electrical issues. I live in 'Little Detroit of the West".

I just rewired my sons 1974 D200's under hood due to so many corroded connectors. On Ebay you can get new Bulkhead male and female connectors that lock in the bulkheads plastic.
His 10 gauge alternator feed to the Amp meter was bad and the return to the battery was totally melted and not charging the battery. His headlight wires were 18 gauge, not the 16 gauge as in the wiring diagram. They are now 14 gauge.

You can replace the stock type flashers with fully electronic units. You can get them at your local parts store. They will plug into your existing wiring. The body of the flasher might be a little larger then stock and might not fit into the retainer correctly however. Your turn signals will flash at a consistent rate. You are doing the correct thing in checking and cleaning all your wiring connection though.

I forgot where I got that schematic, I saved it to my computer. I see now, that little mymopar.com tag on the bottom though, just poked through that site and found it...

link to download the pdf...
http://www.mymopar.com/downloads/79_Dodge_Truck_Wiring_Diagram.zip

edit:
link to the page with the schematics.
http://www.mymopar.com/index.php?pid=24

X2 appreciated

Dave J, I'm north of you, in the Stanwood area.

The truck is in pretty good shape overall. It's bare bones, no A/C, no radio, it has a heater and windshield wipers !
Even the ammeter & bulkhead connections are in good shape. It's 40 years old though and needs a bit of cleanup.

Burdar I put in new flasher dealies for both turn signals and hazard. I can swap the two units and still I have turn signals
but no hazard. Right now the turn signals won't turn off after a turn, so I want to replace the turn switch anyway.
I haven't searched yet for that, I would prefer to find an NOS piece if possible but maybe they are now unobtanium.

Dan Stern (Daniel Stern Lighting Consultancy) had some but not sure if they are the correct ones for your truck.
He posts on FABO and Slant Six forums but you could just look up his website for contact info.


Looking at the full size pdf for the '79 truck,
The turn signal flasher gets power from the run circuit. J10A feeds the fuse. The fuse in turn feeds the flasher via the short connector (F11A)
Hazzard is fed from F38 (prple with white) which comes direct from the battery. So check that for power into the fuse. The hazzard fuse connects to the flasher via F40 (pink). Check that next.

Did you install the original kind or the full electronic ones? When I got my Challenger on the road, the turn signals only worked half the time. I replace the flashers with new "original" style units and got the turn signals to work all the time. However, when coming to a stop, they would flash really slow. The full electronic flashers fixed that issue and they now flash at a consistent rate. You may have other issues but the electronic flashers are a good upgrade IMO. Good luck!

And a cheap 12 volt test light is your friend when working on these old Mopars.

A glass fuse may look good but I gave a few in my tool box that look solid but one end under the cap was disconnected. A test light will show if the fuse is good. If it lights on one side but not the other, toss it.

Stanwood is a 82 mile ride. Thats only 3 gallons of gas ROUND trip on my scooter.

I will be going thru my wiring on my 78 LRT soon. The bulkhead connector is all green. I'll also be doing the Alternator feed straight to the battery and back feeding the AMP meter.

The alternator's 2nd job should be to recharge the battery.
The alternator should connect as direct as possible with the power distribution point(s).

Do not back feed an ammeter:
(a) it then becomes meaningless
(b) the circuit can become overloaded.

The ammeter is for the battery only. It should not also carry the power to be distributed to the rest of the equipment.

If you want to run a wire direct from the alternator output to the ammeter, attach it to the same side as the main splice.
If keeping the original wires, then there are two parallel lines (as shown below). So the load is shared.
If not keeping the original run through the bulkhead, check the size of the wire from the ammeter to main splice. Might be worth taking the unused/ damaged wire out of the bulkead and putting a ring terminal on it. So then there is new heavy (8 or 10 gage wire) to terminal stud, and two older 12 gage wires to the main splice.

could the parallel line diagram you posted be used to install an ammeter where there was none ?
TIA.

As long as no other equipment is between it and the battery, sure!

what would that show ? in other words, would it be worthwhile to do this ?

Whether it would be worthwhile depends on the person!
Witness how many owners don't know what the ammeter shows.

If you want to see whether the battery is getting charged, how much it is being charged and for how long; and whether it is discharging, how much it is discharging and for how long, then this type of ammeter is useful.

Not every car company offered ammeters on their baseline cars and trucks. Some used 'idiot lights' which arguably may grab a driver's attention when something is wrong. In contrast, a gage pointing to any particular point, or even an extreme has to be interpreted as to whether it is normal, abnormal or even dangerous conditions. There's at least one post on the IFSJA forum where TWICE the owner left something on, needed a jump start. The second time he attempted to drive home even while ammeter (which goes to 60 amps) was pegged to charge and he could tell the wires was sizzling. He got lucky and the fusible link finally melted before something flammable lit up.

Now here's the thing. An ammeter alone doesn't tell the whole story.
If we see what appears to be excessive charging, we still need a voltmeter to help us narrow down the cause.
If the voltage across the battery was in normal rangewhile the ammeter is showing this, its probably due to the battery excessively low condition.
In this scenario, we'd ant to try to get the battery on a charger, and if not available, keep the rpms as low as possible so the battery doesnt get hot. (or the wires!)
On the other hand, if the voltage across the battery is at say 16 Volts, then excessive current to the battery would be due to the high voltage driving it. Something is wrong on the regulation side. Either the regulator is getting bad info or its not working properly.

So a dashboard voltmeter shows potential being maintained by the battery or the alternator.
and a dashboard ammeter shows whether battery charging or discharging is occuring.

Hope that makes sense.

yes it does.
however, using a large amp alternator, the biggest [highest ?] rated amp gauge i have seen has been only 60 amps.
how would this figure into the equation ?

I had a major issue when I was running a 120 Amp cop car alternator. It would PEG the dash Amp meter after every start for 1-2 minuets or so. So IF you run not much over the factory old school 45 Amp alternator you are fine but....
What is really needed is a "look-a-like" Mili-Amp meter that has a shunt in the back. When you run say a 90/120 amp alternator only a small portion of the amperage goes thru the miliamp meter but the major amps bypass it thru the shunt.

If you are still wanting to run the factory 60 Amp MAX amp meter with a HUGE amp alternator, you could somehow figure out a by-pass shunt wire to strap across the amp meter so it will still see a discharge/charge. Run a 6 gauge red wire from the alternator to the shunted amp meter with maybe the shunt wire being a 16 gauge and then a 6 gauge black wire to the battery. This will not be 100% accurate but it should work.

Or just bypass the amp meter like what I have done in the past. None of my daily drivers will ever go go a 'POINTS' car show so I run a 2 gauge pod under the dash with a Oil pressure and a volt meter.

Probably because if there's more than 40 amps going to the battery there's a problem - at least in a normal setup.


It depends on the alternator; But if its capable of producing more power, then its more likely to provide a high charging current to a low battery.
Some examples of alternator curves in these two posts
https://board.moparts.org/ubbthread...ories-amp-gauge-re-wire.html#Post2714603

You've probably observed that batteries draws more current when more heavily discharged.
And the closer it gets to full charge, the less current it draws.
This is true as long as the power is available, and the voltage its available at is unchanged.
About 1/2 way down this thread I post a sequence of charging photos with timestamps.
https://www.forabodiesonly.com/mopar/threads/charging-battery-with-alternator-warning.424783/
Notice in the beginning, I manually reduce the power available, dropping the voltage from the charger.

i understand the amperage needed in a totally [or almost totally] discharged battery will be very high, [your graphs are good by the way] and as you approach 40 amps charging, you are closing in on dangerous territory as far as charging goes, but i think my main question is, can you safely use a 60amp gauge on a say, 100amp alternator system ?
this, of course, is using the bypass diagram you posted above, and your wiring system is in good working order.

for the last many, many years, all my wiring [original harness and from scratch] has been centered on using a volt gauge only, [in creating a new harness] and disconnecting the original amp gauge, or converting it to a volt gauge in an original or reproduction harness. now, high amperage alternators are a common addition, and for one of my own projects, i would like to run an amp gauge as well as a volt gauge, but was somewhat concerned about the available amp gauges only coming in at 60 amps. [if a guy has a draw or input of that amount, you have problems ! ]

comments ?