Understanding my heater/blower circuit - Do I have this right?

[Lockleaf]

This is copied directly from my Half Pint build thread, in case some of you don't read the projects. I have a 1971 510 wagon with a complete 1982 720 2wd wiring harness swapped in to it.

 

 

 

I'm working on the last major circuit on my wiring conversion (I think). I'm working on the blower motor circuit. And it's slightly confusing to me so I just need to make sure that I understand it's function correctly. So I drew up this diagram of the two circuits trying to clarify my understanding to help ensure that I wire the 510 blower motor and blower resistor correctly to the 720 harness.

 

 

This is copied directly from my Half Pint build thread, in case some of you don't read the project threads.

 

So as I understand it, 510 is very straightforward. Power from fuse goes through motor in to the resistor, then gets grounded variably through the switch, selecting different paths through the resistor. Ground switching in standard format.

 

The 720 uses the relay. As far as I can tell, the relays purpose is to send power to the circuit without it all passing through the ignition switch. Whenever the vehicle is on, the heater circuit relay is energized and the power from the battery gets connected to the circuit. Power passes through the relay in to the motor. From motor it goes out to resistor, but also has a bypass that sends a full 12 volts around the resistor completely. Like the 510, the switch changes the resistance of path to ground to change the motor speed.

 

Am I understanding this correctly?

 

 

Here is the reality of the 510 blower and resistor wiring. I think just drawing this diagram and typing this message might have finally helped me to understand what is going on here. If I understand it, then I can wire it right. So here we go.

 

Power goes in to motor via blue wire. Power leaves motor through the black wire and goes out to resistor. Black is tied directly to blue white, effectively bypassing the resistor and going out to the switch on fan high speed. Otherwise power goes in to resistor through black, then out via blue/red and blue/black.

 

Hmmm.....

 

I edited my wiring diagram to more correctly reflect how the wiring is actually done in the 510.

 

 

Now I've edited it one more time. I believe this reflects the exact same pathways for electricity, but I've re drawn it to visually appear like the 720 circuit. Someone let me know if I made any errors. If this is on point then I got this bad ride figured out.

 

 

Any thoughts?

 

See this post on my build thread at http://community.ratsun.net/topic/66801-half-pint-z22-swapped-510-goon/page-7

[Laecaon]

This site shows a ton of photos inside the box: http://www.510coop.com/completed/heater.htm

 

Its all the same, Datsun just didnt do a wire splice and instead just terminated the wires at the same terminal.

[Lockleaf]

Sweet. Thanks for the link.

[DanielC]

The resistor is centertapped, or you can think of it as two resistors in series.  On high, the heater switch connects the heater motor to directly ground.  On medium, half, or one resistor is in series with the switch, thus putting some resistance in the ground of the heater motor, and on low, the whole, or both resistors are in series, putting more resistance in the grounding of the heater motor.

 

It would not hurt your 510 to wire a relay like the 720, this would take heater motor current out of the ignition switch.