Alternator not charging 71 D20 4X4

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From: trader_reed  (Original Message) Sent: 3/22/2007 2:51 PM

OK it been awhile but I'm getting ready for the beach season.
My 71 D20 dash wiring is crazy, the MOM switch don't work and I was thinking about removing it, any thoughts? But the big problem is I'm not charging off the engine. My Stock 318 was replaced with a new 318 Magnum and newer alt, dist. ect.. Can anyone draw me a basic wiring diagram for the alt. (alternator wiring for dummies) I want to rip out the old wires and replace them. Oh I'm 99% sure it's not the alt. as it happened to me last year too, but a little wiggling of the wires got me charging again. I want to fix it right this time. Also what fuses are within the charging system?  I fried a ignition control module last summer, Dead on the side of the road! I found the problem and replace the module and all was well. Come to think if it that might have been when I stopped charging again.

Matt
 

From: trader_reed Sent: 3/22/2007 8:16 PM

The engine block is a Magnum but to keep this simple the wiring was kept stock. It has a new distributer w/out points and a newer alternator. I've not messed with it in months a but remember seeing the white ballast resistor but not the voltage regulator behind the engine, I'll have to look tommorow when I get home from work.


 


 

From: trader_reed Sent: 3/27/2007 4:44 PM
Ok so no luck, I bought a new alternator, voltage regulator and tried just wiring it up so it would just charge. I can't get the alternator to put out 14.4V or anything even close. I had NAPA test my old Alt. and they said it was bad so I bought a new one. I tried it and I won't charge, so I brought it back to have them test it and it failed. I had them pull one off the shelf and test it and it too failed. So now that I know there are a bunch of idiots what do I do to get it to charge? I read the wiring diagrams and can't get it to work. Can somebody give me a basic wiring diagram to get this to charge?


 

From: Slantsixness Sent: 3/27/2007 6:25 PM
Matt,
The alternators you have may not be bad. the guy who checked the new ones probably knows less than you do about Mopar alternators.

Heres the deal. you have 2 fields to the alternator. and one output.

So the output you can guess is pretty simple, the big threaded post that the big thick wire goes to....

there are two fields, Field 1 and field 2  Field one is regulated 12v, and Field two is either at ground (charging) or anywhere between up to 13.6V. this varies the alternator fields and supplies outputs.

you can see the schematic in any 1988 and prior all the way back to 1969. Dodge service manual (without fuel injection or ECM).

What you might be missing, is the fact that the Alternator charge wire itself goes directly back to the regulator input, and to the starting relay where there is a Fusible link. the oddity here is that when the ignition is on, the Battery connection is shorted to the IGN or ACC connection, and you will never be able to tell that the fusible link is bad! Check it for continuity between the alternator wire (disconnected) and the Alternator gauge in the dash, and to the starting relay too. You will probably find it open.

Ok. Now I've told you what it could be....

Here's a link to the Valiant site where it will give you some more detail. Please keep in mind that you have a TWO FIELD ALTERNATOR, and it's in the second and further on diagrams, the first diagram is the old thermoelectric, or "mechanical" regulator and single field alternator. These are color diagrams, and should match your rig wire for wire in color, as it was standard color code across all Mopars.

http://www.valiant.org/electrical-diagrams.html

There's even a blurb here about switching pre-1972Dodges over to Mopar electronic ignition.

Tom


   

From: trader_reed Sent: 3/27/2007 7:39 PM
Ok is there two wires that come off the Batt. post on the alternator? And what post on the V/R is the input on the V/R I thought they where reversable? Where is the fuseable link? up behind the dash? 


 

From: DaveVa78Chieftain Sent: 3/27/2007 8:15 PM
I take it you cannot download the chassis service manual available in the members section.  There is a simplified schematic on page 8-35 of that manual.  Because the charging system has to adjust and respond to conditions in the complete chassis (ie lights, heater, etc) there is no simple answer here when discussing hookup.  While the alternator BATT post does lead down to the starter relay (drivers side frame rail), it is not a direct path.  The fuseable link is in that path at the starter relay connection.  One of the altenator field leads goes to the regulator.  The other field lead connects to a junction of wires and which goes back to the ignition switch (key on RUN signal).  One lead off of the regulator also goes to that junction of wires.  Bottom line is you need the simplified drawings in the manual that you can also relate to the chassis wiring diagrams in the manual.  Even someone with experience will need that info to help locate the problem.

Dave




From: trader_reed Sent: 3/27/2007 8:33 PM
I've been looking at the service manual, The diagram I've been using is on page 8-37 What your telling me is that there is a fuseable link, Where in the 8-37 diagram is it?




From: trader_reed Sent: 3/27/2007 8:54 PM
OK I just went out and tested from the disconnected wire at the batt. terminal of the alt. to the + starter relay where the battery cables connect to and I've got continuity. 


 

From: DaveVa78Chieftain Sent: 3/27/2007 10:49 PM
For 70/71, the complete chassis wiring diagram is on pages 8-86 and 8-87.  The Alternator circuit is spread across the top of both pages.  One FLD wire [R22(18OR; 18 gauge orange wire)] goes to the ignition ballast resistor.  The ballast resistor gets voltage from the ignition switch (key in run position).  The other FLD wire [A3(18LG; 18 gauge light green)]  goes to the regulator.  Thats the one that the regulator uses to control current output in the alternator.  The regulator sense wire [R6(18BK; 18 gauge black)] also connects back (same connector as FLD [R22]) to the ballast resistor.  The BAT wire [A20(10BR; 10 gauge brown)] ends up at the battery via the (going backwards from battery) starter relay, to the amp meter, to a junction, up by the ignition switch and back to the alternator.  While that sounds complicated, it is what is on page 8-37.  For the 71 chassis, the overall chassis diagram does not indicate there is a fusable link.  Later years installed one on the wire [S2(10RE; 10 gauge red)] that comes off of the B+ terminal of the starter relay going to the amp meter.
Good luck - Dave


   

From: DaveVa78Chieftain Sent: 3/27/2007 10:52 PM
Should add, the drawing on page 8-37 is a simplified wiring diagram intended to just show you the basic circuit.  The full diagram is on pages 8-86 and 8-87.

Dave



From: Slantsixness Sent: 3/27/2007 11:09 PM
1969,1970, 1971, 1972 at least all have a fusable link. and they are easily indentifiable... theres a tag that says Fusible link. Yes, the service manual doesn't show them until 72, but they're there! and on the m series and p series chassis, they are on the starter relay, although I have seen them on the main interconnect behind the accelerator pedal (remove the carpet cover panel)

Some people have had difficulty downloading the free manuals, sometimes it takes forever, or the server or your own browser settings can prevent the downloading.

nonetheless. to clear something up about the field terminals, there is field 1, and field 2. They are not interchangeable.  the rule of thumb is... if it's not charging, and nothing else is wrong, reverse the connections between field 1 and field 2, and usually, Bang! you're charging. The Components in the alternator and regulator ar strong enough to withstand the improper wiring if that is what happened, so you potentially have done no harm to the system if the fields are reversed. Usually, field 1 wire is too short to reach field 2 and vice versa, except over time, the harness falls apart and the formed guided connection is lost. usually, the Blue field wire goes closest to the BAT terminal on the alternator, provided it's original, and the originally clocked alternator.

Tom 


   

From: trader_reed Sent: 3/28/2007 8:01 AM
I'm 99% sure that's how mine is hooked up, I'll check it when I get a chance. Is there a test with the meter for the V/R and or alternator? Thanks for all the help!!! After I double check my wiring I'm going to buy another alternator from a different parts store.

Could I hook up a one wire alternator with an internal V/R? They make them for Hot Rods right? Just connect the batt. wire to the starter relay and I'm charging correct.

I'm glad I started messing with it before the season or I'd be real mad.

Matt


 

From: denisondc Sent: 3/28/2007 10:05 AM
It is possible to check the alternator with a meter, and I recommend an analog meter. You check the output voltage at the big terminal on the alternator - With the engine shut off and ignition off, it should show about 12.6 volts to ground (the case of the alternator or the block or frame). With the engine running it should show more like 14 to 14.7 volts. The case of the alternator has to be well grounded to the bracket, the bracket to the engine, and the engine to the frame - or things wont charge well. I took the lazy mans scheme and ran a thick copper ground wire from the case of the alternator to the frame. I also replaced the heavy ground wire running between the frame and the back end of the tranny, because it looked feeble. I ran my new one to the lower bolt that holds the starter motor on.
You can measure the voltage between the field-1 and field-2 wires. But, a digital VOM will give you confusing results. The regulation happens by the V/R switching the voltage across the two field terminals on/off several times per second. If the two field terminals had voltage across them all of the time, the alternator would be charging at high current.
The ammeter needle pivots on a tiny shaft that is supported by simple bearings inside the ammeter case. If these pivots points get sticky with dried grease, you might not see much swing of the ammeter needle, even if the alternator were working. A test for this is to turn on the headlights (with the engine not running) and see if the needle takes a nice dip to the discharge side.


   

From: trader_reed Sent: 3/28/2007 11:09 AM
My Amp guage works good, when I turn on the lights it dips well into the - . I get 12.6V with the engine off and 12.3V with it running, So no charge. I will try a heavy wire from the case to the frame to see if that helps.

I'm really liking the one wire alternators but at $200 for a Mopar one it's a little high. The GM one is $85 but I'd have to make new brakets. Any thoughts?




From: trader_reed Sent: 4/9/2007 3:24 PM
All fixed!!! I pulled the Mopar alternator and V/R and replaced them with a one wire Delco-Remy alternator. It now charges at 14.3V and puts out 70 amps. I connected the Batt wire to the starter relay and tied up the V/R wires. Then I ran a large wire from the alt. to the starter relay. I get less voltage drop that way.