Batteries are Overcharging

[fuzzybob]

Hello, my first post and naturally I need some help. Thanks for a great site!!
My MH is overcharging and cooking the batt. I did a search and found a link to DaveVA 78 chieftain's site where I was able to download a wireing diagram and a trouble shooting guide.... thanks Dave. I've put on a new voltage reg and took the alt in for testing.... it tested good. I've opened up all the wireing and pulled the seat to get under the dash. What I've found is, I get a 1 volt voltage drop at the solder joint when I plug the field wire into the alt. I get another 1 volt drop when I plug in the ignition control box giving me a 2 volt drop. I'm sure this is what's causing the over charge but don't have any idea where to go from here. I have a 78 Brave with a 440-3
Thanks in advance for any help, Fuzzy

[DaveVA78Chieftain]

Sorry I have not gotten back to you until now.  Been out of town camping since last Wednesday.  When you say solder joint  do you mean the main the one at the right rear of the engine where all the wires come together (J10 circuit common distribution point)?

1. Bottom of steering column ignition switch connector - known weak spot.  You may have to repair the J10 pin (IGN1).  Corrodes and burns out.  It is the 12VDC source to the solder joint from the ignition switch.
2.  Check Fusible links at Starter Relay mounted to driver side frame rail.  If they are real limber and soft then replace them.  A fusible link is smaller wire size than the wire they are protecting.  The 10 gauge alternator wire is protected by 14 gauge fusible link.  That one also feeds the ignition switch (A20 circuit).

Dave

[fuzzybob]

No problem with the delay, I understand you have a life too.
Yes the solder joint is the J10 at the back of the engine right side. I've checked the fusible links and the plug-in at the bottom of the steering column. I've printed out all of the info from your site and have tried to do all of the tests.
If I unplug the 5 pin connector from the electronic control module (ECM) and unplug the A3 green field wire from the back of the alt then check key on voltage at the J10 joint I have full batt V, 12.5 If I now plug the A3 back into the alt and leave the 5 pin unplugged I have key on 11.6 at the solder joint. If I leave the A3 hooked up and now plug the 5 pin back into the ECM and check key on at the joint it has dropped another 1V to 10.6. The wires from the ECM go to the coil and distrib. would the problem be there?
Thanks for any help, Bob

[DaveVA78Chieftain]

No, problem is on supply side (battery to solinoid, to starter relay, to ignition switch to solder joint).  There is a bad connection along that path that drops the voltage when a load is applied to the circuit.  Connect the components up then start measuring the voltage back along that path.  At some point you sould see a large drop in voltage indicating a bad connection.  For example, say voltage at ignition switch in is 12.5VDC.  With key ON, the IGN1 lead on the ignition switch output is 11.0VDC. You would be losing 1.5VDC across ignition switch indiacting the internal contacts are burnt.  YOu have to follow it back to the battery.  You can start at battery and work to the solder joint, or start at the joint an work back.  Key here is to rember the voltage drop can only be seen when a load is on the circuit.  In other words, current must be flowing to find the problem.

Dave

[fuzzybob]

Dave, thanks for the info.... I think the light has come on. I'll go back and recheck everything with the "current flowing" this time. I'll post back with the results.
Thanks again, Bob

[DaveVA78Chieftain]

One part of this that is not so easy to look at is the ground side.  Make sure you have good cable connections at the battery and the point it attaches to the frame.  Also make sure you have a ground cable from the frame to the engine.

Dave

[fuzzybob]

I have an update and a possible new problem.
Dave, you hit the nail on the head..... power into the ignition switch is 12,5 coming out is only 11.3.  I've removed the switch and it has a part number of 3895095. The dodge dealer can't bring the number up to anything same story with NAPA. Do you or any of the members have part number for a 78 ignition switch? I would think they used it for years in many applications...can't believe the dealer can't come up with something!
The junk yard is a possible option but I'd really like a new part.
Thanks all, Bob

[DaveVA78Chieftain]

Real P/N (from Dodge MH Parts Book) is Mopar 3747092

http://motors.shop.ebay.com/i.html?_nkw=mopar+3747092&_sacat=&_odkw=mopar+switches&_osacat=0&bkBtn=&_trksid=p4506.m270.l1313

Used - http://www.mopartruckparts.com/group-08.html

Google - http://www.google.com/search?q=mopar+3747092&hl=en&gbv=2&prmd=ivns&ei=BbPjT-_JLOH40gHv9qX3CQ&start=10&sa=N


Shop around, lots of people who think collector parts are made of gold.

Dave

[Elandan2]

The ignition switch is a current part.  Just find a parts counter who will look it up in a book rather than the computer.  I had no trouble getting a new switch last year as soon as someone looked it up in a parts book.  Rick

[fuzzybob]

Thanks Rick and Dave for the quick replies.

    With the correct part number and links and the knowlege that the switch is a current part I should be set to go.
Thanks again, Bob