Re: Suggestions on harness for 12v conversion

Posted by HH56 On 2019/1/26 11:02:10

By all means look thru Big Kev's blog for an excellent report on a conversion. There is another poster who just finished a 49 and while he kept 6v, I believe installed a new aftermarket harness. Perhaps he will see your question and refer you to the pertinent part of his blog on the PAC site. One nice thing on your car is Packards of that year and model do not have many accessories so are very simple electrically and do not need a harness with a lot of fuses and circuits if you are going to keep it fairly stock.

KwikWirehttps://kwikwire.com/standard-harnesses/ has an 8 fuse harness which is more than adequate for a stock 200 if you stick with the stock Packard headlight switch with its built in circuit breaker. That breaker alone takes care of headlight, parking, tail and dash lights but may rely on you doing some custom wiring with the new harness in order to feed the bulbs. If you are going to add more accessories such as power windows, door locks, fancy stereos, AC, etc or completely plan on revising the electric layout you may want a harness with more fuses and they have a 14 fuse which would do the job. I have not used their product myself but others have. One thing KwikWire advertises is the use of heavier wire in their harnesses which if there is a chance of the car staying or reverting back to 6v at some point in the future would be the way to go.

Painlesshttps://www.painlessperformance.com/wc/p.php?s=customall is the other aftermarket harness supplier Packard owners have used. They have a few specialty harnesses with a lower number of fuses which might work. Being for specialty use such as off road or racing they might not be a good choice for ordinary street use though. You can visit both sites and download a manual for the various harnesses to see the typical layout and what their recommended installs look like. I know several of the 55-6 owners have used Painless looms but those cars are much more complex electrically than yours and were 12v from the beginning.

A few things you are going to need to overcome on your car is grounding issues to the lights and voltage supply if you are going to keep the stock radio or if the car has overdrive.

On the grounds, Packard relied on contact in the mountings between various metal parts for a ground path. Pot metal and steel frequently rust or corrode and make for poor grounds where they contact. Perhaps the biggest issue when people report erratic light and particularly turn signal operation is a bad ground. If you are not using a harness with separate grounds be sure and clean any bolt and screw connections between pot metal and a fender. The tail light housings and the entire grill area with parking light housings are notorious for issues. Some have actually added hard ground wire connections between the parking light housings and a fender to avoid the grill path entirely.

As to voltage, there is no comparable 12v version on the stock radio and while there may be an option on the OD, it would be expensive to switch so best to figure how to supply them with 6v. A resistor will work for other things such as the heater motor. The gauges in 51 have their own voltage regulator which can work off 12v or there are individual Runtz converters for each gauge but resistors are not the best method for supplying power to the radio or overdrive. The loads on those items can't be regulated very well with just a resistor. You may want to consider a dual voltage layout using something like a 12 to 6v regulator capable of 30 amps or so output (available on ebay) to run those items. There may also be some additional work needed to connect the turn signals since Packard used a plug for the switch connection going up the steering column which will not be part of any aftermarket harness.

Also be aware that things such as the starter motor may be an issue. While there are those who converted and successfully run a 6v starter on 12v changing only the solenoid, there are others on the forum who have had issues with the starter self destructing because the additional torque and speed caused by the 12v slams the pinion into the end housing and eventually cracks the casting nose piece. Packard nose pieces are different and starting to get harder to come by. For that reason you may want to consider having your starter converted to 12v.