Voltage and Ballast Resistor Question

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christopher.brandon

christopher.brandon

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Hello all,

I have noticed that my voltage meter fluctuates with my idle and with the throttle. It reads a bit above normal at normal idle, will kick down a bit when I hit the lights, and will peak out at 40+ when I step on the gas. It used to flux a bit when it was idling, but would go back to center when I was driving. However, now it does not go back center at all.

I am still working on that problem and invite any ideas as to a solution.

In the process of checking things out, I checked the resistance on the ballast resistor, and noticed that the ballast resistor is reading just below 1 ohm (approx. .9 ohms) on both the Primary and Auxiliary terminals. The Hanes manual tells me that the Primary should be 1.12 to 1.38 ohms and the auxiliary should be 4.75 to 5.75 ohms. Does anyone know what a possible cause for this could be?

Just to clear things up, I replaced the ballast resistor about a week ago to try to fix a different issue, but kept it and tested it as well: Same readings on both resistors.

Thanks,

Chris
 
I assume you are talking about the ammeter. Sounds like it's overcharging.

You need to run some simple tests, and determine if it's

the battery

a wiring problem

the voltage regulator

1 If the battery has a a problem, is is down from sitting, it may be charging hard. First order of business is EITHER charge the battery and have it "load tested" and if possible, checked with a hydrometer --- or temporarily substitute a known good battery out of a second car

2 AFTER you know the battery is OK, run the car at an RPM to simulate "low to medium" cruise and measure voltage with a multimeter right at the battery. With the engine warm (the regulator is affected by temperature) the system should "run" at about 13.8--14.2V, not less than 13.5, not more than 14.5

If this is high, you need to run some more tests. Post back to this thread with results, and we'll go from there


ON the ballast resistor, the factory manuall shows the 4 terminal ballast is 5 ohms on the ECU side and .5 (1/2) ohm on the coil side. I believe these changed somewhat over the years, and one other source shows the coil side at 1.2 ohms. I would not worry about it unless it is intermittent or open.

Do you have a factory shop manual for your car? 12V test lamp? multimeter? AND what year/ model we working on here?
 
I changed out the voltage regulator since I had a warranty, and the results are as follows:

Ammeter reads high for about 15-20 seconds
During this time, if you give it some gas, the ammeter peaks out like it used to
After this period, the ammeter goes back to center, and stays steady

I checked the voltage on the battery both off and while running, and my multi-meter reads 10 volts during both tests. I am awaiting a better multi-meter, as the one that I have is an old analog. I have a digital Fluke coming my way in the morning.
 
The ammeter readings sound normal now. Rather than the Vreg itself, the problem was more likely corroded terminals. When convenient, remove your bulkhead connectors and clean each terminal. That will cure many problems. Consider bypassing your ammeter in the engine bay. Many posts on this. If you have a Harbor Freight nearby, free multimeter w/ coupon often.
 
I agree with Bill, and it sounds like your present meter is AFU
 
Bill,

What exactly do you mean by "bulk head"connectors? I am not familiar with this ten. I have, however, started going through, and cleaning many of the connectors.
 
christopher.brandon said:
Bill,

What exactly do you mean by "bulk head"connectors? I am not familiar with this ten. I have, however, started going through, and cleaning many of the connectors.
Click to expand...

Chris the "bulkhead connector", or "firewall connector" is causing a lot of problems for a lot of people. It's the huge rectangular connector where all the wiring feeds into/ out of the firewall. The big problem is, the charging current goes in the connector, through the ammeter, and back out the connector. Even Ma knew this was a problem, because on cars with larger alternators, they added extra wiring with rubber feedthrough grommets, and on the larger cars, finally went to an "external shunt" ammeter

Read this excellent article on why. Look a the simplified diagram down the page which shows the battery and alternator charge path through the connector

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

more here:

http://www.madelectrical.com/electrical-tech.shtml

If you decide to perform this bypass, here's a thread on how some of us converted our ammeters to voltmeters

http://www.forabodiesonly.com/mopar/showthread.php?t=119480
 
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