Hi All,
I posted last week about a No-start/No-spark problem I was having on my 1970 Challenger (w/ Mopar electronic ignition). With the fantastic help and lessons I got from the great people here I was able to determine that it was the ECU that went bad on me. THANK YOU very much for all the help on that one! I picked up a standard OEM (blue) ECU box at a local parts place (figuring I could use it as a spare after I order a new Orange one). I put it in and it fired right up and runs really strong.

Then, just when I thought I was done with the gremlins (this car has not had an electrical issue before in all the time I've had it), I noticed as I was warming it up that the Ammeter at idle was fine (a tad over the middle), but when I gave it some gas (to say 1500 rpms or higher), the needle pegged to the far right of the meter. Letting off the gas, it comes back to where it should be. This never acted this way prior to last week and the ECU failure/replacement. I had charged the battery up fully after all the testing for the ECU stuff, so it couldn't have needed the charging it was getting..

So, I'm wondering now ..
(1) Does it sound like the Voltage Regulator also took the opportunity to give out on me?
(2) If so, is this common for both components to go bad in unison?
(3) Is the fact I'm running the blue (oem) ecu unit rather than an Orange, a possible cause (since it's a Mopar performance distributor)?

Any insight or ideas would be greatly apprecated!!

Thanks again!

(1) yes but 1st take it off/clean it's base/ground. (2) no but when it happens that way it will test your diagnostic abilities (3) not at all. I'd get a new electronic VR & I think you'll be good

Thanks for the quick reply Robert! Ok, I'll clean things up and put a new Voltage Regulator in there in a few days when I get over to the car again.

From scouting the online parts guide for my local chain, looks like Chrysler used the same unit from 70-77 (no difference between elec. ign vs. points ign) so this should be easy to come by. Funny though, they list a basic voltage regulator for around $15 (BWD brand # R296P) and another for almost 3x that price (BWD brand # R296). If anyone thinks one might be better than the other, please let me know.

Thanks much!

You have the flat one w the triangle connector? To my knowledge the flat ones are the same ex the blue MP one is a higher "constant voltage" type that is supposed to be a race only item but people have used it on the street w no issues. Any possibility you could easily post pics of the 2 and any description given along with them.

I was able to download the following pics from the BWD Products site .. But, they didn't have a description other than that it's a Voltage Regulator. From the pics, they look pretty similar except maybe the more expensive one (R296 - 1st one) has a different color insert for the prongs..

Thanks!

..and second one (R296P) :

the're the same ex the diff color on the triangle surround most likely denotes that it is a higher voltage unit. I think if you grab the $15 one you'll be fine.

Sounds good. Thanks again for your help Robert!

You are welcome

Sinitro your not saying the cheaper flat one in the pic is points you mean the $15 one that they are selling is the old style mechanical unit not one of the 2 shown in the pics?

The old mechanical ones only work with single terminal field alternators used up through 69.

It sounds like the alternator is charging with full field current. This could be a bad voltage regulator, or a short in the wiring that goes to the voltage regulator.
#1. Unplug the triangle connector at the voltage regulator, start the car and rev the engine to verify the alternator is NOT charging.
#1a. If in above test, No charging is observed, replace the voltage regularor.
#2. If in the above test the alternator is still overcharging, disconnect the field wire going to the regulator and repeat the test in step #1.
#2a. If No charging observed, check wire for short to ground.
#3. If alternator is still overcharging, there is a short at the alternator. Usually this is just a short at the alternator brush holder.

The $15 voltage regulator is fine if it is the bad part.

Thanks very much for the great info on this! I will run these checks in a few days when I get back over to where the car is stored. I have my fingers crossed it's just the voltage regulator, but I'll post my findings. Thanks again.

Update on this one - it was the voltage regulator that was going bad .. I replaced it with the new $15 one and charging is back to normal now. Much thanks for the help!

One more very newbie question -- when I went to mount the new regulator back on the firewall, one of the mounting bolts still feels loose (spins if I try to tighten it more). I didn't overtighten it to begin with and the holes don't appear to be threaded. So, my question is - how to deal with spinning mounting bolts in the firewall in these situations? I don't think I can get behind there to put a nut on the back, right??? Do I need to go up a size in bolts (It's a 7/16" currently) or are there insider tricks for this ?

Thanks!

Same thing happended to me.

I was able to remove the cowl cover and get a nut on the back.

Also took the opportunity to add a ground strap to the engine.

gotta make the hole smaller. can you tap the flared hole back flat? another trick is to stick some wire in the hole to take up space. ruin a sparate ground to the case of the VR and you wont have to worry about the ground connection anymore

Put a nut with a built in star washer on the back side and you won't have a problem again.

Thanks all for the ideas on this one! I'll check this weekend when I get to the car and see if I can get in back of the firewall to try to get a nut on it. I am trying to recall from memory the access points to that area - maybe through those vents near the wipers ..

Thanks again!

just remove the plastic cown screen on the pass side and intall a nut with some kind of washer to bite into the metal to supply a good ground.

you can use either a captive serrated tooth washer or just a plain nut + external tooth washer for the same effect. once in , just paint them flat black then only you and your therapist will no any better