Ignition problems, 1969 Chrysler OB 75 hp

[RGShore]

I have a 1969 75 hp Chrysler OB engine that has no fire. I believe the battery was hooked up reversed as the CD (powerpack) does not fire. I have ordered a new CD unit but am concerned about the rectifier as a troubleshooting manual says that the CD unit and the rectifier would be damaged if the battery connection was reversed. I do not know if the rectifier is damaged or needs to be replaced. It does not show any visible signs of damage. I am not sure of what the function of the rectifier is and if it would affect the engine running at any speed or does it function to keep the battery charged? I have limited testing equipment and am hoping that the engine will fire when I install the new CD unit that is supposed to arrive tomorrow. Any information on the purpose of the rectifier and if it can be tested without the engine running would be appreciated. Thanks.

 

[Frank Acampora]

Re: Ignition problems, 1969 Chrysler OB 75 hp

I am not too up on what years had what equipment. If you have the red, square, selenium rectifier, it should also have a "trip" regulator with it. this was usually bolted on the exhaust cover right near the rectifier. This rectifier can be checked with a volt/ohm meter.

If you have the black finned box, this is the Motorola regulator/rectifier. You need a special meter to check it. However, if you temporarily disconnect the battery while the engine is running it should show at least 12 volts at the red terminal. If not, or if the engine stalls, it is bad. only run the engine with the battery disconnected for the shortest perion of time necessary to check this. It is bad for the alternator. New Old Stock is very pricey so you would be best looking for a used one.

These regulators and rectifiers supplied DC current to recharge the battery and while the engine was running they were the primary source of charge for the ignition system. I think that if you have the selenium rectifier, it is relatively bulletproof and the thing that would be damaged by reverse polarity would be the transistor in the trip regulator. You can run this rectifier without the regulator but you would need to keep checking battery water since eventually the battery will be overcharged and will start to "boil" off water.

Regardless, even if they are not functioning, the engine still can use power from the battery to charge the ignition and should run very well. Trouble is that you will drain the battery so eventually the engine will stall. These electronic ignitions use a lot of power so the battery will drain relatively quickly.