Pacific coast Datsun Posted December 13, 2007 Report Share Posted December 13, 2007 Minor problem here. On my 74 620 my hetaer hasnt worked ever since i got the truck back on the road. So i took the cover off the heater & cleaned out alot of leaves & crap & while it was off i looked under to see how the wiring is. I saw a round silver metal part on the side of the heater that has 2 wires coming out if it. Then on the heater itself theres 2 flat connectors w/ no wires connected to them. Under my dash theres a "few" wires not connected to anything & im wondering which ones i need to connect to get it working. I saw the diagrams on www.the620.com but the wires under my dash appear to be different colors. Help... i can figure it out w/a bit of advice from you guys :D Quote Link to comment
datzenmike Posted December 13, 2007 Report Share Posted December 13, 2007 If your wires all have their connectors on them just keep trying till you get the right ones hooked up. I find that all are slightly different so you can't mis wire anything. The wires going inside the fan probably go the a tiny coil of bare wire that provides resistance to give a slow fan speed. It's mounted in the air flow so it doesn't get too hot. High speed is connected directly to the motor. Power goes to the motor and through the resister (for low) or directly to ground (hi) through the two position fan switch. All I could find was a Blue power wire to the fan motor and a Black ground wire to the fan switch. There are at least two other wires going between the switch and the heater and fan assy. but not labeled. Quote Link to comment
Pacific coast Datsun Posted December 13, 2007 Author Report Share Posted December 13, 2007 The 2 wires coming off the round part DO have connectors on them. Of the 3 of 4 wires left only 2 have connectors on them that MAY go to the 2 connectors on the heater core. Ill get out there & see what i can figure it out. Quote Link to comment
OL YELLER Posted December 15, 2007 Report Share Posted December 15, 2007 Mark...(and datzenMike)..you are correct about the Blue power wire and the black ground; Mike....now then there are three wires from the heater control to the resister coil wire you mentioned Mike...they are Yellow, Yellow w/red stripe, and a black wire..Ground I suppose......I pulled these wires from a 620 this morning so I could show you what they look like Mark...as you can see the yellow and black wires are connected to one spade and the yello/red wire is the other side...........hope this helps 1 Quote Link to comment
DanielC Posted December 17, 2007 Report Share Posted December 17, 2007 All three of the 521 pickups I have have got three speed heater motor. The blue wire goes to the heater motor, and the black wire coming out of the motor grounds on the side of the heater case. There are three wires going to the resistor in the heater case. The switch sends electricity through the whole resistor, and then to the motor for slow speed. For medium speed, the switch sends electricity through half of the resistor, and for high speed, the switch sends electricity just to the fan bypassing the resistor altogether. The schematic I have for the 521 does not show the resistor, just the three wires in the plug attached to the heater. It does show the heater as being grounded, so the three wires supply power. Quote Link to comment
Javin Posted June 8, 2011 Report Share Posted June 8, 2011 Search function is amazing! I am sorry I keep digging up old threads but stuff like this sometimes needs a second life. I was curious about the 2 wire thing as well since i have 2(!!!) heaters and neither of them have had anything plugged into it since I had them. After rebuilding them I was left wondering what the little piece was for and even more so, what the wire was all about and how it was supposed to be connected. Thanks for the Oics Ol Yeller. They were exactly what I was looking for! Quote Link to comment
Pacific coast Datsun Posted June 9, 2011 Author Report Share Posted June 9, 2011 Damm what an old thread :D Guess i should have updated it. I recently got my blower motor to work but only on high speed [lever pulled out to 2nd position. I also replaced the heater control valve & both hoses [new]. It blows hot & defrost works..kinda :rolleyes: Quote Link to comment
Javin Posted June 9, 2011 Report Share Posted June 9, 2011 Did you ever pop that little piece out that ol yeller shows? BOTH boxes that I have the spring looking wire had come unattached to the other lead. Bet if you check, it will be undone as well! Hook that up and you will have low speed again. Did you ever get rid of anything on the radiator? I know that was a common issue as well. Quote Link to comment
Pacific coast Datsun Posted June 10, 2011 Author Report Share Posted June 10, 2011 No i didnt pull the resistor at the time...Im ok with the way it works now plus i doubt Ill need a heater out here :cool: Quote Link to comment
Hrvat9 Posted January 31, 2017 Report Share Posted January 31, 2017 Good call on the coil being disconnected, just got mine sorted :D Quote Link to comment
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