help! chargeing problem since mad bypass!!

Ok, I did the " mad " bypass a month or so a ago on my sons 74 Duster, I was diligent to follow the instructions with proper solder and splice connections as directed when I was done I started the car and it ran fine however I didn't check the charging system output, I know it was ok before I started because the car was driven daily last summer, so we are getting ready to take it to the exhaust shop tomorrow am as it has open headers now and I discover this problem, here is what I have done to diagnose.., checked charging system with volt and ammeter, the battery which was new last year and just came off the battery charger last the other day, I have 12.2 volts static and while running, the alternator output at the + post is the same I have three spare alternators and to the best of my knowledge are all functioning properly, I swapped with all three tonight, same results, I pinned the wires at each end of the bypass ie: from the alternator + post to the fusible link at the starter relay and had continuity, ie: no blown link, as a hail Mary I even had a spare good voltage regulator and tried that as well but same results, I was reading through my service manual trouble shoot guide and it suggest high resistance in the fuse-able link, the only place I strayed a bit from the " Mad" bypass instructions was using 14" gauge fuse-able links going to and from the starter relay, could this be my problem?, what have I missed?, any help here would be good as I have an appointment at the exhaust shop at 9:00 am tomorrow and I am about 8 miles from the shop too far to drive with no chargeing system.

Do yourself a favor if you don't, get a factory service manual. The 73 manual "should be close" You can download it here:

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

Charging problems fall into just a few major "sections"

1.... Actual defective alternator, or regulator

2....Wiring troubles in the field circuit

3....Wiring troubles in the output line circuit

4....Mostly over charging (over voltage) due to voltage drop (poor connections)

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So do some quick checks. Here's a simplified diagram, from MyMopar

http://www.mymopar.com/index.php?pid=31

HOW IT WORKS. Ignition power from the switch is fed to the VR IGN terminal and to one of the two field terminals on the alternator. The power to the VR does two things, power the VR, and act as "sensing" voltage

The VR controls "the amount of ground" so to speak through the green wire.

1..........Determine if the alternator can charge. Unhook the green field wire at the alternator, hook a clip lead to the now exposed alternator terminal and hook to ground. Turn the key to "run," engine OFF. Take a voltmeter and check the blue field connection at the alternator, still hooked up, with your clip lead grounded on the opposite terminal. See if you have "close to" battery voltage at the blue wire. If you like, you can hook / unhook/ hook up the clip lead and in subdued lighting, should see a small spark, indicating the field is conducting power

If you don't see conduction, (no spark) and or have no voltage at the blue wire (key on) then you have found part of the problem, or all of it. Find out why you are not getting V on the blue wire with the key "in run."

Meanwhile, you can "substitute" for the blue wire by running a clip lead to a battery connection (starter relay large stud) to the "blue" field terminal.

2.....Now start the engine and slowly bring up RPM while monitoring battery voltage. V should increase, depending on how discharged the battery is, to over 13 or 14. Don't let the V get above 16.

If this does not happen, move your meter to the large black output stud. Again, bring up RPM. On a good unit, this voltage should be close to what you saw at the battery PLUS as much as 1, 1 1/2 volts or so.

IF YOU get quite high voltage at the output stud, maybe 18 or more, but low (12 or less) at the battery, YOU HAVE an open in this output wire


Let's say it DOES charge OK with the above tests. Maybe remaining field circuit problem, or bad VR?

3.....So, hook wiring up "per normal." Unplug the VR connector and inspect. Should be tight, and not corroded. "Rig" a way to jumper across the two wire terminals in the VR connector, such as small machine screws.

Now, unhook the BLUE field at the alternator and ground that exposed alternator terminal. With the key in run, you should again see a spark as you unhook / hook up the clip lead. With the clip grounded, you should now see "about" battery voltage on the GREEN terminal at the alternator.

Now repeat your run test. If it brings up voltage as before,

First scrape clean and re--mount the VR. It MUST be grounded!!! Must be clean and tight. Use star lock washers.

With everything normal, if the above tests give positive results, replace the VR.

Check the blue field wire for power when the key is run/on position.

Bad ground on VR is another. The VR grounds through the case. No ground, not going to work. Use a jumper wire from batt - to VR case.

Ok, I appreciate that however with the "mad" bypass the circuit is no longer exactly the same I do have a factory Dodge truck service manual from that vintage and I think the wiring is basically the same, but my belief is the problem lays with the fuse able links I have installed, it is really the only different thing, what would be the harm in removing them to test my theory?

Sorry my post went before I read your last post, those were both excellent post and step by step you are VERY helpfull, thankyou, it is 10pm here now and dark, the car outside and with no exhaust so I will do these test first thing tomorrow and let you know the results, thanks again

ok I just had a thought, after we got this car back together from installing the new intake and header I accidentally let the blue wire that went to the choke relay touch ground and it lit up the harness, I then repaired this wire and ran it to the choke and it worked, ( supplied voltage ), it went into a white connector at the fire wall, ( where it melted ) and through the harness along the valve cover, I simply took the wire out of the connector and ran it to the choke with a new blue wire, is it possible that after it connected to the choke where it tee'd off that it went to the field circuit which is now not connected, hence an " open "?, if so then there is my problem

WHOO HOO, GOT IT!!, MONKEY DANCE!!, THANKS, you hit the nail on the head, I went back to the car, ( with my flashlight ), so the blue wire goes into the white plastic connector at the fire wall and out the other side then from there it goes into a wire harness that travels along the valve cover, half way along that harness wrapped in tape a splice of that blue wire comes out and supplies 12v to the choke resistor, ( the wire that melted ) then it continues in the harness, ( i did not know this ) and terminates as the blue field wire on the alternator, I know this because a few minutes ago a did a continuity check between the blue field wire connector and where the dead ended wire was that I cut out of the harness at the white connector, all I have to do in the morning is run a new blue wire from the field to where I tapped into for the choke and I should have my charging system back, again THANKYOU!!

See electrical isn't so bad... :banghead:

Hope it works out the way it appears.

I'd use a butt connector and some shrink tube to protect the spliced area.

yeah it worked out fine, I got up early this morning and did the repair, charging like a dream now, got down to the exhaust shop for our 9:00 appointment, be glad to get some pipes on the open headers, pretty noisy ride to the muffler shop, glad I was in the chase vehicle, lol, haven't heard the exhaust as its still in the shop, as far as electrical goes I actually like it and am fairly good at it to but, when gremlins are thrown in your face with hours to spare its a little frustrating, the clue on the blue wire lead me to the problem, thanks again for the help guys. oh and btw, yes all connections heat shrinked and wrapped.

Very good. Do yourself a favor while your mind is still on this. Get the thing all warmed up, charged up and "normalized" and measure battery voltage with engine running at a good fast idle. Make sure it's somewhere between 13.8 and 14.2, and not below 13.5 nor above 14.5

This will tell you if the VR has a voltage drop problem in the harness

ok good idea, I will do this after dinner

Just a quick question while this thread is still up .... when you say that the VR must be grounded and to use star washers. Are you meaning to grind to bare metal the area around the two holes on the back of the VR and around the two holes on the firewall and then use a star washer between the VR and the firewall before mounting it. I was going to run a wire from the VR to the block. But if the above is ok ...would rather do it that way.

You can use wire to the block. The thing is, the block is sometimes poorly grounded to the body, which is yet another aspect of this problem

Think in your mind the "path" of the ground.........and each potential "bad connection along the way

Battery neg post / cable clamp

Corroded inside the cable at that point.

Same down at the block

Many factory cars had a minimal ground PIGTAIL from the NEG battery clamp to the fender sheet metal, so THAT is a point of trouble.

Many had, or "had added" one or two no 12 or so wires / straps from the block to the firewall.

On V8s you have the same holes in the rear end of the driver side head as you do in the front on the pass. side. I like to use a a short "ring to ring" or starter cable. Bolt to the rear of the head, and bolt either to a bolt through the firewall, or to one of the master cylinder studs.

Thanks 67dart ...but was my question on thoughts correct on using the star washer on the back between the VR and firewall and grinding around the two holes on the back of the VR and firewall holes correct. I have no problem running a grd to the back of the head but want to know if I should also do the grind.

If you don't want to grind any paint off the firewall, then run a ground to the block. I'll assume you have a main battery ground wire running to the cylinder head.

fyi, 14.4 at fast idle, thumbs up, and car sounds good with new 2.25 dual exhaust installed today!

SB69GTS said:

Thanks 67dart ...but was my question on thoughts correct on using the star washer on the back between the VR and firewall and grinding around the two holes on the back of the VR and firewall holes correct. I have no problem running a grd to the back of the head but want to know if I should also do the grind.

Click to expand...

Yes, scrape the paint off the firewall and off the back of the VR. This way it gets a good ground. I don't believe Del, mean's sandwich the star washer between the VR and firewall. I'm pretty sure he means use it to hold your VR on. It will hold it on nice and firm.

I'm sure there are many many ways to do this. The stars "bite" into the paint. There's actually no reason at all NOT to use them between the firewall and VR, but I guess you don't have to

The whole deal is, the VR to be accurate, MUST see EXACTLY what the battery voltage is doing. It must be exactly at battery "same as negative" or within a couple of tenths of a volt.

Likewise, the IGN terminal must ALSO be within say, .2--.3V of battery positive and often IS NOT. This is a VERY troublesome deal with these old girls. "In the path" from the battery to the VR, are several connections which can drop the voltage.

Please understand that the MORE LOAD (wattage, current) that you place on a circuit, the LOWER the voltage becomes.

So the path, "generally" is........Starter relay (battery) --- through the firewall connector --- to the ammeter and through it ---- to the welded splice ---- to the ignition switch connector -- through the switch contacts --- back through the ignition switch connector (now on the blue IGN 1 "run" line) --- BACK OUT through the firewall connector, and finally, split off to all underhood loads

Depending on the year, this can consist of

ignition circuit

VR "IGN" terminal

Alternator field (blue) 70 and later

electric choke if used

idle solenoid on some cars (six pack, etc)

distributor retard solenoid on some models

and depending on year, model, "some other" smog doo-dad

All these loads draw CURRENT and magnify a bad connection in things like the bulkhead connector and or ignition switch. Anyplace there is a termination.

There has even been (rare) failures of the famous "welded splice."

THE ABOVE is the NUMBER ONE problem of over-voltage in charging circuits. If your battery "run" voltage is up around 14.7 to 15 or more volts, this harness problem is the very likely cause.

A little knowledge can save your day. A few alligator-clip jumpers might get you to work and back for a week.

My 1964 Valiant lost ignition and wasn't charging on the drive home after buying it. I ran a jumper from BATT+ to ballast resistor and another jumper to alternator field (single terminal). It was only a 70 mi drive so I left it charging full. For longer, I would have monitored battery voltage and unplugged the alt field after >14.5 V. BTW, when I later looked at the ignition switch, in place of the factory plug a gomer had used individual spade terminals, some of which fell off.

Thanks Guys ...and yes ...the ground from the battery is running from the battery to the head. I will mount the VR to the firewall ...use a star washer and a ground wire to the head on the rear drivers head. Just wanted to know if the back of the VR and the firewall where the VR mounts would require to be grinded for more protection to be safe. One of these days she should be on the road ...lol

I always run a custom ground wire from the VR mount to a more solid ground than the sheet metal screw the factory relied on. Note that newer cars have special grounding studs scattered around the vehicle. Relying on tentative body connections caused many issues in 60-70's cars. Even 70's Darts changed to a dedicated ground return wire for the headlamps. My 65 Dart relied on a sheet-metal screw right behind the headlamp connector (I improved that).