Tip For Field Testing Ballast Resistors

[The_Handier_Man1]

From: HeavyHaulTrucker  (Original Message)
Sent: 2/7/2005 2:36 AM

Ever been out in the middle of nowhere and the engine won't start?  You think it might be the ballast resistor, but not quite sure?  Here is a quick & dirty way to check it -- and if that is it, this will also get you into town in a pinch.  An old-time Dodge mechanic told me this one, and I have used it a couple of times.

Cut a piece of coathanger wire about 6 inches long, and crimp a spade connector on each end.  For the dual ballast resistor, make two of these "jumpers".  Unplug your ballast resistor & plug in your "test jig", then try to start the engine.  Make sure you don't touch the "jumpers" to anything grounded, or to each other.  The coathanger wire provides enough resistance to drop the voltage so that you are not putting straight 12 volts to the coil -- doing so will kill the coil pretty quick from heat build-up.

If it starts & runs, then your ballast resistor is shot -- and your "jumper" will allow you to get to the parts store to get another one.  If it doesn't start -- or starts but won't run -- then something else is the problem.

John



From: 70winnie
Sent: 2/8/2005 10:51 AM

I've been told to always just carry a spare ballast resistor!



From: bboat101
Sent: 2/8/2005 2:29 PM

Do they fail very often?
What are the symptoms of a bad ballast?
Where are the located on the M300?
On my old roadrunner, I think I remember seeing it on the inner fender wall.
brian



From: Slantsixness
Sent: 2/8/2005 2:57 PM

This also applies to non-electronic ignition engines (but why would you use points since the conversion is sooooo easy)! But you will only be looking for a "two pronged" ceramic ballast resistor, instead of a "4 pronged" wider resistor.

Symptoms include:

1.No ignition in the "run" position (but it will start and fire up in the "start" position.... not to be confused with running out of gas!)
2. No ignition whatsoever
3. Intermittent sputtering and backfiring while running (but it usually doesn't last very long and then reverts to one of the above symptoms at next startup or overnight.

Locations I've seen the ballast:
Class A winnies:
1. next to the electronic ignition module and regulator on the transmission "bell".
2. Inside the front access door on a metal plate. (left or right side) (seen a few like this.)
3. Mounted to the heat sheild on the drivers side near the spark plugs (318 only)
4. Mounted to the Engine intake manifold (unusual).

Class C minis:
1. Almost always next to the ignition module just to the right of center near the junction block and the wiper motor.
2. The only other place I've seen one is against the left (drivers) fenderwell frame on some, but it's rare to see it there and usually has been relocated because of some non-factory (dodge) accessory.

Also keep in mind that a lot of times, the ignition modules and resistors are mounted in other than these places because some previous owner thought it was better there, so, as in one car I had, I've even seen it mounted to the dash on an old valiant!

Regarding John's jumpers:

These are only to get you to a troubleshooting point to find out if they are indeed bad. Do not drive down the road indefinitely with just the jumpers. Doing this will result in overheating of the ignition coil, ignition noise in the radio, and premature failure of the (really hard to kill) ignition module. In the worst cases, the excess spark current can cause damage to the voltage regulator, too.

On non-electronic "standard" ignitions not using the resistors will burn the points out along with the overheating of the coil and still can damage the voltage regulator.

Slantsixness



From: OldEdBrady
Sent: 2/8/2005 6:44 PM

CARRY A SPARE?!?  Some people jsut have to do things the easy way, don't they?






From: HeavyHaulTrucker
Sent: 2/8/2005 8:14 PM

Ed, this tip was tendered with the intent of giving you some information that would get you into town after you looked for your "spare" & couldn't find it.  Then you realize that you forgot to get another "spare" the last time it took a dump on you! 

John