The Dodge Challenger Message Board

Can someone tell me how much amperage the stock style alternator would have had on a 70 challenger?
I've heard 37amps to 64 amps.
Can I get away with a 60amp or 75amp without changing the OEM harness?

Thanks

The amps is what it is capable of delivering. It is not what it "puts out". It only puts out volts.

Your cars electrical systems dictate what current (amps) is drawn. A stock system will draw the stock amount of amps. As long as your alternator is rated higher then that is fine.

The higher amp rated alternators often used a bypass from the output terminal straight to the battery.
Certainly helps take load away from the dash and connector block

Adrian Worman wrote:The higher amp rated alternators often used a bypass from the output terminal straight to the battery.
Certainly helps take load away from the dash and connector block

Not sure they did that from the factory as it by-passes the ammeter in the dash. But it is a good idea to do that anyway.

So, what would the rated amperage be from the OEM style I currently have? Can I go with a higher output without damaging the wiring? (I imagine the VR would take care of any over-voltages)
I think I need an alternator with a higher Idle current than what I have, so I can finally eliminate this pulsing of my dash/ head lights.

One more time.

Alternators do not put out amps. It does not matter what rating it has as long as it is higher than the car demands.

You are talking nonsense.

If the VOLTAGE is "pulsing" it will effect the lights.

It could be that your idle speed is not high enough to over come all the resistance in the 45 year old wiring and connections. So increase the idle speed if you have not got a constant idle voltage. Or make your wiring more efficient.

My mistake, Dave. (I should have phrased it properly).
I meant voltage.
My idle is at 900RPM which seems fine. I can increase the idle but it'll be too much I think.
Wirewise- How best to increase the wire efficiency? I can't afford to rip out and replace the main harness at this point, and have already done this:

INSTALLED RELAYS ON BOTH HI/ LO BEAMS
RAN 8G FROM ALTERNATOR TO BATTERY
BYPASSED AMPMETER
IMPROVED/ UPGRADED ENGINE GROUND(S)
REPLACED DASH LIGHT DIMMER, HEADLIGHT SWITCH AND HI/LO BEAM FOOT SWITCH

What's next?

You could try making a new engine harness Chuck, just by replacing all the old, corroded and heat damaged wiring you will instantly have much less resistance in the system.
Go and check out a few auto-electrical suppliers, the stuff is really good value if you don't mind a weekend of do-it-yourself work

On the Engine harness, are we talking larger gauge wiring or simply fresh new wiring?
Any suggestions of who to shop? Websites?

The voltage regulator dictates what voltage the alternator puts out. Not the alternator rating.

First things first.

What is the voltage over the battery at idle? Can you see if it is steady or not?

So tell me what the voltage is and by how much it is changing.

900rpm should be plenty to run an alternator even if the wiring was a bit flakey.

Dave-

Meter on Battery:

AT IDLE: 13.6V-14.2V
INCREASED REV: 14.50V-15.2V

Meter on VR:

AT IDLE: 15.0V-15.25V
INCREASED REV: 15.4V-15.76V

Again, ALL suspected switches/ dimmers have been replaced. VR was replaced with no change in voltage results.

Well you have to ask yourself why is the voltage at the VR higher than the voltage at the battery? It should be exactly the same as both are coming from the output of the alternator.

Also the half a volt variation in output isn't enough to make the headlights flicker.

I'm stumped, to be honest.

&*#!%$

Strange part is....this didn't happen for a good 4 months and all of a sudden...
Could it be a bad diode?

cv70chall wrote:Strange part is....this didn't happen for a good 4 months and all of a sudden...
Could it be a bad diode?

It's possible Chuck, you could swap out the alt and VR with some known good stuff, only way you'll find out

Can't be the alternator.

Like I said- with the exception of the engine harness- I've swapped out everything that has been suspected.

Now what? Punt?

Resistance reduces voltage. If the voltage is higher at the VR (too high actually) and lower at the battery, then there is a higher resistance between the alternator and the battery than there is between the VR supply and the alternator.

Or the battery itself is bad and acting as a resistor.

Battery is a new Sears Die Hard Gold. Load tested/ tested and was fine.
Wire is 8g (not 10g) from Alternator directly to starter relay. Too large a wire?

Bigger the wire the lower the resistance. So it is not that.

Put one side of your volt meter on the negative of the battery and probe around with the other on various live points to see where the volts jump up from the 14 volts at the battery to the 15v you found at the VR.

Check what the alternator is putting out at idle by measuring that directly. It should be exactly the same as your reading at the battery. If it is than you cannot have 15v at the VR.

Have you got a good engine ground connection?

dave-r wrote:Bigger the wire the lower the resistance. So it is not that.
OK

Put one side of your volt meter on the negative of the battery and probe around with the other on various live points to see where the volts jump up from the 14 volts at the battery to the 15v you found at the VR.

1. Do this volt meter check (above) with the engine at idle?

I have TWO grounds. One from the head to the firewall and the second from the block to the battery.

2. Lastly, which terminal (or terminals) do I probe on the alternator? Obviously the positive post and which other post?
Sorry if I seem ignorant about this- I'm "electrically challenged"
LOL

You should have a ground strap from the block or head to the batt ground on the inner front fender or rad support too Chuck.
Check the alt output at the large batt terminal, the same terminal that you took your bypass wire from.

Yup, I have the ground strap from the batt to the rad support as well.
Will check alternator tonight.

dave-r wrote:Resistance reduces voltage. If the voltage is higher at the VR (too high actually) and lower at the battery, then there is a higher resistance between the alternator and the battery than there is between the VR supply and the alternator.

Or the battery itself is bad and acting as a resistor.

This is a scientific truth and a critical point to take to heart if you see voltage dropped across connectors. Resistance reduces voltage because the point of resistance absorbs the energy necessary to overcome the resistance and the result of that absorbed energy is heat in the connector. This is why Mopars have melted firewall connectors, melted engine harness connectors, etc. I have experienced this first hand. The connectors contacts get corrosion in/on them and this makes them less conductive (more resistant) and so they have voltage "dropped across" them and they heat up a lot, which can increase the voltage drop more ....it cascades until the connector melts or sometimes actually catches fire.

I don't know about flicker but almost every odd wiring issue I have had was sorted by cleaning the connectors and making sure the ground was good - as long as you've not messed with wiring otherwise. If you have been changing things you could have undone something. If that's not possible, I'd go thru all of your connectors (engine, firewall, front lights, etc) especially those exposed to the elements to give them a cleaning with a chemical cleaner and elbow grease with some sort of abrasive to get the tabs and the female socket clear of oxidation. Then put in a bit of electrical contact grease. That's a poor man's new wiring harness.

Oh, you can turn on everything and touch/feel the connectors for heat. Sometimes this will show you where you have trouble - just feel them after few mins of operation. When it's really bad you can smell them...that's not a good smell in multiple ways.

Thanks for the tips. I've checked the main harness connectors at the firewall (good) and can check the connectors at the head and tail lights if you think that will help. I'm pretty sure I cleaned them prior to assembly but it can't hurt to re-check.
So, if a single headlight plug is corroded or dirty- it can affect everything and result in all the lights flickering?
Even the radio display flickers alittle.

???
Re-checked alternator and i'm getting 14-14.6V so it's healthy. All grounds are newly done-
firewall to head bolt
batt to rad support
voltage reg to head bolt- AND- one of the screws is now bolted to the firewall

Is there any other event that happens before, during or after the pulse? Is it only when driving or idle too? is there anything that seems to be partnered with the pulse?

Were it me I would test the voltage level at the headlights w car running and lights on and compare this to the battery voltage to see how much voltage is lost in resistance from the battery to the headlights. Also, connect the voltmeter to the headlights and see if you can detect/observe what the volt reading does when the pulsing of the lights happen. Determine if the voltage drops during the pulsing and by how much.

Might investigate that headlight relay you said you installed if it was done before the pulsing started. If done after then prob not suspect. In fact any wiring and new elec components added before the issue started should be inspected.

A few yrs ago my brake lights would work fine and my turn signal worked just fine but when I did the turn signal and brakes neither worked. This did not cause a pulse but it did stump me a good while as the brake lights seemed to work. Voltage test at rear of car showed the problem. When I measured voltage at the rear I was losing like 5 volts to resistance in corroded connectors (not one single connector but just the addition of them - firewall, real harness connector, etc). Cleaned connectors fixed that issue.

Nothing happens before or after the pulsing. It didn't occur until about 4-5 months after the car was completed. I can have the car running and only have the radio on- and the lights on the radio are pulsing- without any of the car lights on.
Also, the headlight relay system was installed after the pulsing started in the hopes of fixing it/ taking less of a toll on the system- and it didn't help at all as far as the flickering goes.
Aftermarket stuff only an alarm (installed before the car was done) and radio/ amp, but those are separate.
I guess I can re-check the bulb connectors at the rear lights as well as the harness back there. Can't hurt.