Not Ron or Bill!
I am presuming that you are using a series resistor pack to allow you to run a 6 volt motor from 12 (actually more like 14 volts)? Reading between the lines, your 3 x 2 ohm resistors in parallel has an equivalent resistance of 0.666 ohms, so your design motor current to create an approximate 6 volt drop across the resistors is 9 amps. At 9 amps your heat output is going to be roughly 54 watts so those resistors are going to get really, really hot. The heat dissipation rating of high wattage resistors is based upon the assumption that the resistor is mounted on an heat conducting substrate (metal chassis) that is held at a specific temperature. Mount those resistors in free air and their temperature will go through the roof. So, first observation is that the resistors need to be mounted on a large metal substrate (the car body) and make sure that nothing meltable / combustible gets close because they will likely still get quite hot.
My second observation is that using voltage dropping resistors for this type of application is very mid 20th century. My initial reaction would be to fabricate a simple pulse width modulation control just like the blower speed control on just about every car built in the last 20 years. This could be done using a 555 timer and a power transistor for the equivalent of about $15 Cdn. With a little fiddling this could be set up to operate as a variable speed control. If you are disinclined to mess with electronics, the other product of the late 20th century is the modular buck/ boost power supply. These are high efficiency devices that are available in a wide array of input and output voltage options and they are reasonably low priced. I can't advise whether this one is any good; but, it gives you an idea of what is available
https://www.amazon.ca/Converter-Regu...ag=googcana-20
As a further observation, if you have more than one 6 volt device that you want to retain, I would be inclined to put in a single buck converter capable of supplying the total 6 volt load and power it up with the switched 12v from the ignition switch (through a fuse). Then run a separate 6 volt supply network (with individual fuses) to the remaining 6 volt devices in the car. This avoids the initial start up hick-up that some converters can have on initial power up. It also allows you to mount the single converter solidly on the body for heat dissipation purposes. Buck converters are typically high efficiency devices (>90%); but, they still generate some heat and electronic components don't like heat.
The other reason to use a buck converter is that they are regulated (insensitive to load current). Whether your blower current is 9 amps or 5 amps you will get 6 volts out. If your measurement of current draw from your blower is incorrect, the voltage drop across your resistors will not be 6 volts which may result in unexpected operating characteristics. The buck converter will be unaffected by your measurement uncertainty as long as it is sized to supply the maximum current.
All this presumes that the PV was negative ground originally.