Author Topic: Hot ballast resistor  (Read 6055 times)

Offline Tonefiend

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Hot ballast resistor
« on: March 16, 2010 - 08:05:10 PM »
I know this thing is supposed to get hot, but skin melting hot after 2 starts and 15 seconds of running?

I noticed it was wired differently after I got my car back from the shop where they replaced my distributor.  The car still does not run. I made it home but it got progressively worse, now it won't even stay running.




Offline Bullitt-

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Re: Hot ballast resistor
« Reply #1 on: March 16, 2010 - 08:14:56 PM »
3-bucks  will get you a new one
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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Offline Tonefiend

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Re: Hot ballast resistor
« Reply #2 on: March 16, 2010 - 08:17:28 PM »
3-bucks  will get you a new one

Thanks Bullitt.  This one is fairly new. I don't have any objection to putting another one on there i am just curious if they get this hot.  I burned the crap out of my finger just touching it for a split second.

Offline Bullitt-

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Re: Hot ballast resistor
« Reply #3 on: March 16, 2010 - 08:21:25 PM »
Is this a two sided resistor?...If so I wonder if they reversed the run side to the start resistor.
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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Offline dodj

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Re: Hot ballast resistor
« Reply #4 on: March 16, 2010 - 08:28:07 PM »
Thanks Bullitt.  This one is fairly new. I don't have any objection to putting another one on there i am just curious if they get this hot.  I burned the crap out of my finger just touching it for a split second.
Toooo hot! Better compare the wiring to a diagram. You may have a short circuit condition. High current through the resistor will give you a lot of heat.
How did that play out at the shop? Charge you for a new distributor and it doesn't run?
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline Tonefiend

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Re: Hot ballast resistor
« Reply #5 on: March 17, 2010 - 01:15:48 AM »
Yes it is a 2 sided resistor.  Long story short the car has an electronic conversion.  Originally it was using 2 one sided resistors.  I swapped it out to a 2 sided resistor that would come with an electronic ignition.  Here are before and after pics. 

Also, I cannot say without looking at the car that they changed anythng on the ballast resistor.  It looked like it to me today, I will have to double check to make certain.



 

Yeah I paid them to fix the car.  They put a new distributor on it and it worked until I got it home. 


« Last Edit: March 17, 2010 - 01:30:07 AM by tonefiend »

Offline UKcuda

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Re: Hot ballast resistor
« Reply #6 on: March 17, 2010 - 04:21:21 AM »
Quote
Is this a two sided resistor?...If so I wonder if they reversed the run side to the start resistor.

I believe the double ones aren't actually a start and a run side, the "start" circuit is wired to bypass the smaller resistor on both the single and the double systems.  I think the extra 5 ohm resistor on the doubles is to do with the background power supply to the early modules.  I expect on the later 4-pin ones they simply integrated it within the box.

Anyway, it is still possible they have wired it up wrong.  There seems to be a lot of wires on there it's hard to see exactly.  They maybe just shoved the wires on and it started so they thought "yup that's OK"

The module looks quite new so it possibly doesn't need a double resistor in any case - pull the plug, if it's only got 4 pins you only need a single ballast.

And by the way, I think your voltage regulator is upside down - don't worry though, the sparks won't fall out.
'72 'cuda

Offline Chryco Psycho

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Re: Hot ballast resistor
« Reply #7 on: March 17, 2010 - 04:38:47 AM »
go back to a single resistor you only need the blue 12v & brown connected

Challenger - You`ll wish You Hadn`t

Offline Tonefiend

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Re: Hot ballast resistor
« Reply #8 on: March 19, 2010 - 01:19:47 AM »
go back to a single resistor you only need the blue 12v & brown connected

What do I do with the other wires?  The loose wire coming off the bottom left is going to the electric choke.  I am going to pull that off the fuse block.


The resistance on the bottom one is 1.1 ophms. The top one is 5.3 ohms.  I put the old oen back on the top position that read .8 ohms and the car still does not run.   Now it will barely start and is getting progressively worse.  It's at the same point it was before I had the distributor replaced. 
Could the ballast resistor take out the coil or another component like the relay or ecu?


Offline Chryco Psycho

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Re: Hot ballast resistor
« Reply #9 on: March 19, 2010 - 02:10:52 AM »
the blue wire is 12v feed & the choke can be connected to that
the coil should be fed through the 1 ohm resister , the second resister drops voltage to the ECU , only the original ECU had 5 pins , if yours has 4 the wire ,green with red trace is feeding nothing at all
check for a .008 gap in the dist & proper ground for the ECU

Challenger - You`ll wish You Hadn`t

Offline Tonefiend

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Re: Hot ballast resistor
« Reply #10 on: March 19, 2010 - 02:45:20 AM »
Thanks Cryco, I am going to be able to spend some time this weekend to get this figured out. 

Can you tell what ECU I have?  Would it be a good idea to upgrade to the performance ECU?

Offline Chryco Psycho

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Re: Hot ballast resistor
« Reply #11 on: March 19, 2010 - 03:03:29 AM »
Can't tell what ECU you have , is there a part # on it ?
a performance ECU might help or could be a waste of $$ , if the problem is something else it will make no difference , most Ecus are good to 6000 rpm or so , I doubt you need more than that

Challenger - You`ll wish You Hadn`t

Offline Bullitt-

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Re: Hot ballast resistor
« Reply #12 on: March 19, 2010 - 10:18:31 AM »
  I wish I knew what I was talking about but just thinking this through the only thing that really uses power in all this is the coil...I could see a bad coil might be drawing to much or a short to ground.   If you have another coil to swap or at least test the one you have.

Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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Offline UKcuda

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Re: Hot ballast resistor
« Reply #13 on: March 20, 2010 - 05:53:27 AM »
If it's the usual Mopar ECU set up I think the coil primary should be about 1.7 ohms, not 3 - 4.

The ECU in the pic looks too new to be five pin.  If it is 4 pin then whoever wired it up with a double ballast likely didn't fully know what was what.  So I think you may want to start from scratch to be sure you have it all correct.  Then you can lose a few of those wires.

So first unplug the ECU and check it's got only 4 pins on the module.  To diagnose the ECU connections you just need to understand and check what each of the four wires is (should be) doing (since your problem is ballast related you might like to skip checking the ECU 'til later and check the coil connection first - see below) but while you're in there better to check it all out. 

If the ECU plug has five wires don't worry, it will be obvious from the position of the "missing" pin which wire is doing nothing (as CP says it should be the green with a red trace).  But remember, on a 4 pin ECU there are still five connections, the 5th one being ground to the casing.

So on the plug you should have 4 (active) wires - this is what they do:

2 of the wires are from the pick-up coil in the distributor.  They do not connect to anything else at all (you can get them to run with these swapped over but there is a "right way round" which runs better);

1 wire is a basic 12v supply (this is power supply to the ECU and nothing to do with power to the coil, so it should always be a straight 12v except when the ignition is off when it will be zero, it doesn't go through the ballast at any time - the ballast has nothing to do with the ECU on a 4 pin system);

1 wire goes to the -ve side of the coil (this is what the ECU switches to ground to energise and de-energise the coil).

You can easy find a wiring diagram on here somewhere to see which is meant to be which, but make sure you know what you are looking at - it's quite easy to see a picture of the socket and accidentally think you're looking at the plug - they are of course the reverse of one another.

Now you can see if what you've got is what it should be.  Unplug the distributor connection (on the stock wiring there's a little connector that can only go one way) and you can just check those two wires match up correctly with the ones in the ECU plug using a test light or something, same applies to the coil -ve wire (disconnect it first so you don't see a false result from anything else).

Checking if you have a constant +12v at the ECU is not so simple, but at least it's easy to check you have some kind of +ve feed with the key on run and on start (if the car starts and runs at all then there must be at least something there, they will run even if this is connected through the ballast, I know because I tried it - it would run fine and then stall at idle if I switched on the lights - LOL).

Then the last piece of the jigsaw is the +ve connection to the coil.  With the key on start it should be direct and on run it goes through the ballast first.

Basically there is a +12v wire from the ignition switch that goes to the coil side of the ballast when you turn to "start" and another wire that goes to the other side of the ballast when you are either on "run" or on "start".  On stock systems they are blue and brown.  With these wires disconnected from the ballast you can use a simple test light to check they are going live at the right time. 

Now you can understand what's going on with all these connections and you will also understand why the wire to the the coil side of the ballast is continuous with the +ve side of the coil and the wire to the other side of the ballast is continuous with the 12v pin at the ECU.

As a diagnostic aid you can wire things up separately, for example, you can disconnect the +ve side of the coil and just run a separate temporary wire straight to it from a definite +ve supply (like the battery) and fire her up - you'll still need the key on "run" to power the ECU, and turning off the key should still shut it down, but be ready to pull off the temporary wire just in case it doesn't !.  And don't leave it running like that more than a minute or two or things will start to get hot.

BTW - standard bullet connectors will fit nicely with the ECU pins for testing purposes.

And don't forget the ECU has to be grounded - when I was playing with mine I had it clamped to a stud on the engine.



'72 'cuda

Offline Tonefiend

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Re: Hot ballast resistor
« Reply #14 on: March 20, 2010 - 11:22:39 AM »
Thanks!!!  I am headed to the car right now with a buddy of mine to try to get this sirted out.  I will rewire the b.r. and ecu. I will let you know how it goes.