hi
im having a voltage problem. it jumps randomly from 14-18. then it will stabilise fora bit at 14. ive tried 2 new regulators and have instaled a brand new altenator. still happning. any ideas

Get the battery load checked.

Does your regulator have a good ground? If not it will go to full charge and stay there.

Check and see if the V/R connectors have spread-out and not making good contact....happened to me.

Chrysler did a bad thing to us when they set up their charging system. The biggest design issue is that they chose to run the main feeds from the battery and alternator through the firewall bulkhead connector and then onto the ammeter. Electronics 101A teaches one that every connection is a potential problem and this circuit is a prime example of that theory. In addition to running the main feeds through the bulkhead they also ran the regulator “sense” wire, which is susceptible to the same issues as the main feed wires.

Good Ground connections between the Battery, engine and body cannot be stressed enough. Failure to confirm these before proceeding will have you chasing your tail and bruising your forehead on the closest wall.

The basic function of the charging system is controlled by the regulator. The regulator case requires a good ground.

The pre 70 vehicles used a mechanical style regulator with one field connection on the alternator. The mechanical style regulator is considered to be inadequate by today’s standards and is best replaced by an electronic version, which is available from a number of sources. The mechanical regulators by design are not capable of maintaining a constant voltage and lead to problems with items such as electronic ignition conversions, stereos and a multitude of other accessories. A mechanical style regulator is easily identified by it’s resistors on the backside. Mopar performance offers an electronic replacement but it’s reputation is spotty. Wells also sells one through Autozone under part number VR706. This regulator functions by looking at the available voltage on the “sense” line and then varying the ground going to the field windings in the alternator thereby regulating to alternators output.




The 70 and later vehicles used an electronic style regulator with two field connections on the alternator. One of the field connections is tied to ignition switch/regulator voltage (sense line) while the other gets a variable ground signal from the regulator. By varying the ground the regulator is able to control the alternator output


How to check the system.

A quick check is to hook up a DVM across the terminals of the battery with the engine running at about 1500 RPM. Ideal conditions will give a reading of 13.8 to 14.2 V although readings as low as 13.5 and as high as 14.5 are acceptable.
While observing the meter turn on high draw accessories such as the head lights and blower motor. You may observe a momentary dip in the reading as the system adjusts for the additional load requirements. If the system is functioning well, the readings will be very close to the previously measured numbers. If not prepare for a trouble shooting session.

Most problems in the charging circuit usually result in one of the following conditions

1. Flickering ammeter. Usually due to intermittent connections in the circuit or a flaky mechanical regulator. Bad grounds or lack of a body to engine ground cable can also contribute to this condition.
2. Undercharging. Move the DVM to the BAT terminal of the alternator and check the reading.
a. If it is still low then look for a bad alternator, regulator, grounds or poor connections between the alternator field connections and the regulator
b. If it is higher than the reading obtained at the battery, look for faulty connections anywhere between the alternator BAT terminal and the battery positive post.
3. Overcharging. Move the DVM to the “sense” terminal of the regulator and check the reading
a. If the reading is still high you have either a bad regulator, alternator, problems in the field connections or a ground problem
b. If it is substantially lower you have a poor connection between BAT terminal of the alternator and the sense line. This is causing the regulator to think it needs more output from the alternator which results in the overcharging.

Most likely causes for the above can be found in the following areas.

1. Corroded or loose contacts at the bulkhead connector. The main feed lines carry a lot of current and dirty or loose connections create resistance impeding the flow of the current.
2. Dirty or loose connections at the Ammeter
3. Worn ignition switch contacts or poor connections at switch
4. BUBBAFIED wiring harnesses. IE: Butt slices, improperly crimped dime store connectors, u haul connectors etc. Any repairs made to the main feed line(s), regulator sense line or alternator field connections should be soldered and shrink tubed.
5. Crappy replacement battery terminals.
6. Bad alternator/regulator or both

TIm

Thanks for taking the time to key this Tim. My R/T cooked some wiring and this is useful. Added pwr windows, cut-outs, AC, and electric fuel pump taxed the 69 stock 40 year old components.

Your welcome Dennis,

The part I left out deals excatly with what you've experienced.

Adding Hi draw accessories like A/C, Boom box stereos etc can overtax a system that was only designed to produce 35 to 40 amps on a good day.
one then needs to look at a higher output alternator. But while doing so one needs to be aware that changing to a 65 or 100 plus amp alternator may require going to larger wires on the main circuit. IE: from the battery terminal of the alternator, to the ammeter, from the ammeter to the starter relay battery terminal.
Also some of the ammeters were only rated for 40 or so amps and putting anything more through them will blow them like a fuse.
hope this helps.
Maybe one of the mod's can archive the info. The systems are actually quite simple and easy to trouble shoot with the previously posted info.

Tim

i 2nd the archive suggestion!!!!!

Definitely archive this. I am not good at diagnosing electrical stuff and this makes perfect sense.

thanks for all the replys very helpfull. will look for all of the problems

In addition to TJP's excellent comments, DO NOT ever assume anything. Back in the day, I've found one of my friends cars with bad/ broken connection INSIDE the molded wire ends at the ammeter connections.

Another friends car had a bad internal splice in the under-dash harness. He thought I was nuts. I tore his entire dash out looking for a "wiggly" ammeter.

Also be suspicious of things like the connector on the back of the ignition switch. "Wiggle" tests help.

thanks im working on it today and starting with grounds

Great set of diagnostics from TJP. Would like to add one more cause to the ammeter jumping: intermittent cell short in the battery, usually due to sulfation. Monitoring the battery voltage will show it dipping (a cell short can never make the voltage go up) and the regulator trying to compensate.
As has been said before, grounds in a 30 year old vehicle are always suspect as are the firewall connections.
Another "Bubbacation" point is the large (about 12 or 10 gauge) red wire on the connection between the steering column wiring and the main harness in the dash. Look for discolored delrin (nylon)connectors and darkened plastic wire jackets. Replace if needed.
Examine all heavy gauge wires and connectors for the green copper corrosion and clean them or replace them. (Radio Shack http://www.radioshack.com/search/index.j...leaner&sr=1 and a toothbrush do wonders). Wiring fires will cause huge amounts of damage!
The ammeter and fusible links are the weakest part of the Mopar charging/electrical system. Proper care and they will last you another 30 years.
Craig

i think i got it fixed. after replaceing many firewall terminals and a fuseable link it seems to work great. will have to take it on a trip to know for shure. thanks