Re: Today's Packard Mystery - Rear Defroster

Posted by BigKev On 2016/2/1 12:50:13

It could be that there was an outside supplier of those that made them in different configurations. Looking at the 51-54 service manual, they show only the two wires coming from the motor and no heater element. The Parts Manual only list one part number.

I wouldn't wire it up with the front blower as I often use the front blower for forced fresh air, especially in traffic. Total load would be less than 10 amps with the motor and the heater element. Which I will power off of a relay and micro-switch trigger from the "defrost" setting on the dash vent control lever. So basically dash vent lever is in defrost position, it will turn on the rear defroster as well.

I have a gaggle of wiring I need to run from the dash to the trunk to support the A/C setup anyway, so I will run it with those wires. I just need to measure out the distance to calculate the wiring gauges I need at the various AMP loads the defroster will need and the right and left two-speed blower motors. Also the wiring for the thermostat for the compressor clutch.

The plan is to make it so the compressor will only cycle on if at least one of the A/C blowers is running. So that will use a relay and four diodes to accomplish that. Also, the thermostat has to agree, as well as the A/C safety switch, and of course the actual dash A/C switch.