Ballast resistor testing

[Tori]

Not finding what i'm looking for in the search, but am currently reading several posts....

Just bought this Hi-Rev ECU http://www.ebay.com/itm/MOPAR-Hi-Re...ler-340-440-318-360-383-/222590478709?vxp=mtr
and with it came some pretty stern warnings and things to check.

First to check was that the ballast resistor is working. Ignition on, take voltage reading at coil. Should be 7.0v-9.0v, i'm getting 11.74v
If i take an ohm reading across the ballast resistor i'm getting 1.4ohm Is that correct ? too high ?
I did this test with the new ECU disconnected.

FWIW, i have what i assume is a stock Mopar electronic distributor, and a stock externally regulated round coil.

 

[Mopars & Missiles]

There are different values of resistance for ballast resistors, but yes, 1.4 ohms is about right for a lot of the common replacement ballasts.

 

[Tori]

Thanks, can you advise on why my voltage is too high at the coil ? I also notice i don't have two + wires at the coil. So, i would assume it's not wired correctly and thus i'm not getting 12v during cranking ???

 

[texas69bee]

http://www.mymopar.com/downloads/1971/71SatelliteGTXRoad RunnerA.JPG
http://www.mymopar.com/index.php?pid=81
Double check your coil. Some setups do not require a ballast resistor based on coil selection.

 

[Tori]

I have a two terminal type. Stopped at O'Reilly and measured a new one. 1.4-1.5 ohms.

Some of the searches i read mention .5 ohm resistor, and .85 ohm What is that about ?

 

[Glenwood]

if the coil is energized, the circuit should have about 3-4amps flowing where a voltage drop of about 5 volts across the resistor would bring the voltage down to about 7 at the coil. If your ign controller is not connected, how are you getting voltage to the resistor?

 

[66Satellite47]

I took a look at my wiring diagram for my old "blue box" from the Mopar Bible. It seemed to stress you need to have the proper combination of coil, ballast resistor & ECU. Best check with manufacturer about the coil & ballast resistor.

 

[Tori]

if the coil is energized, the circuit should have about 3-4amps flowing where a voltage drop of about 5 volts across the resistor would bring the voltage down to about 7 at the coil. If your ign controller is not connected, how are you getting voltage to the resistor?

I'm not getting voltage at the resistor. My readings of voltage were at the coil.

 

[Glenwood]

I'm not getting voltage at the resistor. My readings of voltage were at the coil.

I think your reading voltage from the ignition key switch which i think bypasses the resistor momentarily when starting.
Plug the ign control module back in and check the voltage again at the coil. Mine reads about 7v with the key on.

 

[Tori]

I think your reading voltage from the ignition key switch which i think bypasses the resistor momentarily when starting.
Plug the ign control module back in and check the voltage again at the coil. Mine reads about 7v with the key on.

Yes it does. But i'm not measuring while cranking. Measured with key on only.

 

[Glenwood]

Not while cranking, just key on. If the ign module is connected and there is no voltage at the resistor and nearly 12v at the coil, the module doesn't seem to be working. Is the module grounded properly?

 

[Tori]

The module is currently NOT connected. Instructions weren't clear weather to have ECU connected or not during these tests, just that you can ruin the ECU with too much voltage.

 

[Glenwood]

It shouldn't hurt the module with the engine not running as the voltage won't exceed the battery

 

[Tori]

okay, i'll give that a try on lunch in a few hours. Thanks for the help. I'll report back.

on a different note, i just found out (called BWD's tech line to find out if the coil im using is mounted correctly) that the coil i'm using #E39P BWD brand is supposed to be mounted vertical. - i have it laying down.

 

[Glenwood]

okay, i'll give that a try on lunch in a few hours. Thanks for the help. I'll report back.

on a different note, i just found out (called BWD's tech line to find out if the coil im using is mounted correctly) that the coil i'm using #E39P BWD brand is supposed to be mounted vertical. - i have it laying down.

That's probably to help prevent oil seepage as these coils are oil filled. That should not affect the windings, there's just a primary and secondary winding like a transformer and they don't care what position they're in.

 

[Tori]

That's probably to help prevent oil seepage as these coils are oil filled. That should not affect the windings, there's just a primary and secondary winding like a transformer and they don't care what position they're in.

Isn't it a concern for how it cools itself ? If it weren't a concern, why do they make the two types ?

 

[khryslerkid]

Checking the voltage on my coil, (dual points) I disconnected the yellow wire on the starter relay, hooked up the volt meter to the coil, then read it in "run" position, then in "start" position.

Would that work with the electronic system?

 

[Tori]

It is my understanding, YES.

 

[Tori]

Sent the seller a note regarding the proper test procedure, this is what i got in return:

"No, that's with everything plugged in. W/o the module connected, there's no load, so you are basically measuring battery voltage."

So, i'll check this and report back.

 

[Tori]

okay, so with the ECU connected, i get 6.09v at the coil. Engine running 8.36v

The 6.09v is lower than his recommended 7-9v What can i do to increase that ?