88 w100 conversion question about ignition and charging system
 

Here’s the back story on this truck. Was originally fuel injected and was converted to carb prior to my purchasing it. I put a new engine in and now I have a charging issue. They had modified the alternator bracket and installed a Chevy alternator with an internal regulator. I am a factory type of guy that likes to be able to buy parts off the shelf if I have an issue si I installed the correct bracket and alternator. I wired the external regulator per specs in the conversion kit. Problem is overcharging. I have already replaced the regulator twice. Verified good ground and actually added an extra one to the battery. It charges at 16.2 volts off idle @nd about 15.5 at idle when the blower fan is on high. With the f@n off and lights on it reads 15.5 and when I turn the fan on it jumps back up to 16.2. All new parts including battery are being used. The distributor was also converted from factory to an accel module and coil since the computer is gone . Any help is appreciated I’m scratching my head,,,,,!!!!!!!!!!!

Hello

As someone that has done the GM alternator swap on two of my W200 trucks I must say I'll never go back to the stock charging system, the added performance is too great but, I can also understand wanting to keep things original.

Perhaps this diagram will help:

http://www.mymopar.com/forum_images/pic2.gif

Since you've already checked out the ground and replaced the regulator. Then next thing I would check would be the ignition switch controlled hot wire as this is what the regulator uses as a voltage reference. If that wire is experiencing an excessive voltage drop the charging system will try to compensate for it... thus the overcharging.

Other than that, you might take the alternator off and have it tested at your auto part store. Especially if it's a reman unit, those things come with a life time warranty for a reason.

Hope this helps.

Hello, thanks for the info You are 100% correct I checked voltage and it was only 10.9 coming from the ignition key on . So any idea if I replace the ignition switch it will come back so I don’t have to install a toggle switch thatbill probably forget to turn off and on lol

Well, it may not be the switch itself. It could be the wire or its connectors (like at the firewall bulkhead). It would be hard to tell without more testing.

You could try running a new wire from inside the cab, bypassing the bulkhead connection and splicing back into the regulator connector.

But, if a 88 is anything like a 77. that same (red?) wire also powers the ballast resistor, ignition coil & module. If that is true your ignition system is probably also starving for power. Not good, that will shorten the operational life of the module.

If both your ignition and voltage regulator are sharing the same wire for power, I wound install a relay that was triggered by the original wire. The relay could feed power directly from the hot block or battery to your regulator and ignition system. This would ensure they see full power to operate correctly and efficiently. Be sure to use an appropriately sized fuse.

hope this helps.

edit:

Does this truck use an amp gauge or voltage gauge? Dodge was the last of the big three to switch over to volt meters.

The amp gauges are also another weak point on these trucks electrical system. I bypassed mine. I had an amp gauge get so hot it slightly melted the plastic of the gauge cluster.
I had a friend with a 68 Plymouth Satellite, that the engine would die if you turned on the headlights before I bypassed the amp gauge.
Remember if the amp gauge completely fails the truck shuts down.

Is it possible to send me a schematic of how you did it? With the relay? I have installed all aftermarket gauges so not using the factory ones at all so need to make sure they are also somehow dosconnected and out of the equation. The wire to the ballast resistor only has 10.9 v with key on so I am figuring I need to reword it all and eliminate any potential issues. Like I said it was a RBI and the P.O. changed it in a backyard way he just cut wires and spliced stuff with different colors etc . A real mess . It is carbureted now and has electronic ignition. Also rigged with the accel kit that you can only use their rotor not a off the shelf part . Ugh so frustrating cause I want to simplify the entire engine bay harness

I can try to explain what I did but, the details maybe different as I'm sure your truck has a different wiring harness being it original had an ecm computer. It would be best if you can get a wiring diagram for your vehicle application. This will help you make sense of whats left of your harness.

Alright here we go. Lets start with this diagram

https://www.allpar.com/fix/miscpix/ignition/1.gif


The stock electronic ignition systems used in the 70s requires the use of a dual ballast resistor to protect the coil and module (ecu box) as these devices where not designed to see the full current/volt the electrical system can provide.

However, it is necessary to temporarily bypass the ballast resistor during starting to allow full power as the voltage drop is too great for the ignition system to function with the starter is engaged.

If you are running an aftermarket ignition system that supports a full 12 volts, the ballast resistor is not necessary and can be eliminated. If you do that, be sure to join the "Start" and "Run" wires together so the ignition gets power during both switch conditions.

In my case I run a gm hei ignition system so, I joined my wires. If you use a ballast resistor you'll only be concerned with the "run" wire for relay control.

Here is a schematic of a general purpose 5 pin automotive relay.

http://www.grumpysperformance.com/relay4.bmp

So, basically the wire that is currently being used to power a device for example your volt regulator or also your ignition system; depending on how your truck is setup will be used to turn the relay off and on instead so, it would look something like this:

30: fused protected wire coming from your hot block or battery positive (if your powering the ignition system too, I'd at least use a 12 gauge wire)
85: Relay Coil Ground (anything metal)
86: This is your trigger wire to activate the relay. This would be the hot wire that is currently powering the device(s).
87: Normally Open/Off Contacts. You connect this to the device(s) you wish the relay to power.
87a: Normally Closed/On Contacts. Not used.

I couldn't find an online electrical schematic for your exact vehicle application but, I did find a wire diagram for "1986 150/250/350 Pickups and Ramcharger with 6 and 8 cylinder fuel injected engines" on the repair/help section of the autozone website. Not sure how off it is.

http://repairguide.autozone.com/znet...5280052c69.gif
If this diagram is relevant to your truck:

It looks like the alternator was originally regulated by the computer. Thus the reason for the alternator swap.

What alternator did you go back with? It looks like your application uses either a Bosch or Nippondenso unit.

Did the truck already have a firewall mounted voltage regulator or did you add one?

It looks like the ignition system doesn't use a ballast resistor, which would make sense because fuel injection requires a hotter spark.

The ignition coil gets power from a ECM controlled relay called the "Auto Shutdown Relay" via a Dark Green/Black wire and the fire trigger for it is at pin 2-12 of the ECM via a Black/Yellow wire.

Again I'm not sure if this diagram correctly shows how your truck once was.

The Accel kit you spoke of.
Is it this? https://www.holley.com/products/disc...uct/parts/2030

Good Morning Men... I'm Not going to hi-jack the topic. Just want to add one note.
Kat: I am pretty sure the OEM Alternator in 1988 is controlled by the PCM for output... I think thats why you are hindered with the charging problem, The alternator wants to run full bore because its not getting the information back from the PCM to back off... Going to the GM "SI" unit was a good thing, and yes you can get those every easy. But I also understand why you might wont to move back to the OEM.

880: From what I can tell is got you headed in the rite direction for your fix.

Good Luck Keep us posted. I'm Out... Carrie on Men... :)

Thanks for the note RacerHog. I have no experience with the later model trucks.

When I was researching for alternative alternators for my trucks. I remember the Nippondenso unit used on later model Chrysler models was an option and required minimal modifications but, went with a SI unit because of greater availability in auto part stores

From what I can tell the denso unit still requires the use of an external voltage regulator. It has 2 terminals for the field control like the earlier "round" and "square back" units. Supposedly the electronic dual-field regulator is compatible.

From what I understand the regulator basically makes and breaks the connection rapidly to one of the alternators field terminals.

So, if a voltage regulator is not connected the alternator will not charge. If the regulator is malfunctioning, not wired correctly or there is a short circuit it could kick the alternator into full field.

https://www.allpar.com/history/mopar/electrical.html
http://www.slantsix.org/forum/viewtopic.php?t=28160