heater

[slayer]

:confused: so heres the thing. someo ne that owned this truck before me ran the heater motor directly to a switched hot lead so as soon as you turn the ignition on the heater fans comes on full blast. so i am assuming that means some thing had quit working in the whole fan system.

 

after looking at the diagram http://www.the620.com/data/dat620-1978.pdf

i have decided that i have no idea what i am doing so i am looking for a little help

 

so the actual heater controls i ma assuming have been changed out at some point due to the fact the wires are Yellow, Yellow w/ red stripe, and black and on that diagram i do not see those colors having to do with the heater at all. now in the photos below i see what i am assuming is some sort of relay. i am not sure if one leg is commected to the switch and the other is connected to the motor but i am assuming that is the way it would work.

 

if some one could give me some reconstruction advice that would be great

 

[Bleach]

if those tabs on the fan motor are what turn it on, just run a manual switch.

Hook up a relay with wires right from the battery. The wire that turns the relay on should be a 'switched' wire that only has power when the truck is on. Also, that switched wire is where you install your toggle switch.

 

The fan motor can then be turned on and off by hand, but only can be left on if the truck is on. (when the key is turned off, the fan motor would then turn off even if the toggle switch is on)

[slayer]

those tabs are not on the motor i think they are a relay but i am not sure. the black and blue wires right behind those is the motor. i am trying to take it back to the way it was ment to be and replace any thing that is not working. and in that first photo the blury two yellow wires are the ones that come from the stock fan switch and are hooked to nothing currently

[fiveNdime]

Yeah. I would do a switch. Black should be ground. Since I am very unfamiliar with the 620 wiring system I wont guess where the other two go. Is the heater a stock unit? Like I said unfamiliar with the 620. If not, then what you probably have is a one speed fan. Then its simple. One is the ground and one is the power. In that case you could wire up a switch between the battery and heater to turn it on or off. You dont have to wire it up to a relay if you don't want, since a relay is a switch in itself, but it will give you no control of on or off. Make sure you put a inline fuse before the switch, which you can purchase at a local hardware store as well as the switch. I also noticed the blue and black thats coming out of what looks like the motor. where are they going?

[slayer]

everything apears to be stock with the exception of the actual heater controls. and i only say that because the colors do not match up.

[fiveNdime]

I assume you dont have a stock heater switch. Right?

[fiveNdime]

If the only two wires for your heater are right there then try this.

 

Take a test light and see if one or both are hot wires. Test the wires with the ignition in the off position. Test the two wires. Turn the ignition to the on position not the accessory position. Test the two wires. Let me know what happens. One, both, or neither may be hot in any of those 2 positions.

[slayer]

well i can tell you right now neither will be hot. there is nothing going in to the switch and nothing coming out of the switch. none of the wire are hooked to any thing. they are just striped and hanging there.

 

 

and when i pulled out those tabs it looks like it might be some sort of thermostat

 

[fiveNdime]

Is that the blue wire that has the larger red one connected to it? The factory switch has a rheostat built into it. This is how you get your different speeds. If you dont have your factory switch then your best bet will be to wire in a toggle switch unless you get the factory switch. Wire in your own hot wire. Ground the black to a good source like the body.

 

That coil thing looks like a resistor of some sort.

[moparvwfreak]

LOL!!! i had the EXACT SAME ISSUE on my 620. i kinda got mine working but i am not sure if its totally right. low speed doesn"t work. i may have teh yellow wires backwards, or the resistor coil may be bad. but heres a pic that may or may not help to much.

 

 

i disconnected the 2 black wires and the one off hte switch went to ground, the other black was tied in with the solid yellow. that went to the black off the heater fan itsself. the 2 yellows i jsut put on the coil spades. i hope this helps a little.

[slayer]

is there any way you can show a bit bigger picture?

 

and so the blue off the fan connects cirectly to the blue from the wireing harnes? so the whole switch is to control the ground? i would have never guessed that.

[moparvwfreak]

is there any way you can show a bit bigger picture?

 

and so the blue off the fan connects cirectly to the blue from the wireing harnes? so the whole switch is to control the ground? i would have never guessed that.

 

click on it. it will bring up a bigger pic. yes. the blue goes to blue on the harness nad the ground is controlled by the switch. i had the exact same problem with my 73 620. thats the weird design but it works. i will try to take a better pic when i get fresh batts in my camera.

[slayer]

now that i clicked on it, it is plenty big enough... i am headed out to give it a try i BRB :)

[DanielC]

I only have a 521, but I am going to assume the heater wiring is somewhat similar. The 521 has a three speed fan, I believe the 620 has a two speed fan.

The blue and black wires on the back of the heater motor are exactly what they seem to be. Ground the black one, apply 12 volts to the blue one, and the heater fan goes full speed.

There is a resistor on the back of the heater. When you switch the heater to low, or medium speed, the resistor is put in series with the heater motor, and the fan slows down.

I have some factory original service manuals for my 521, with wiring diagrams. They match most of the wiring on my 521, but there are a few differences. Most of the wiring diagrams for the 521 I have found on the internet are not even close.

 

Sometimes Datsun switches things on the ground side of devices. 510 headlights do this. It is entirely possible that on a stock 620, that when the key is on, or in accessory position, the heater motor has 12 volts applied to it, and the heater switch is in the ground wire from the heater motor.

Low speed, the heater motor current goes through the resistor, through the heater switch, and to ground.

High speed, the heater current motor is grounded by the switch.

 

It also appears that there is a relay in the heater circuit, by the diagram.

 

On a 521, the power for the heater motor goes through the ignition switch. On the 620, Datsun might have decided to have the ignition switch just turn on a relay that supplies power to the non ignition accessories you would normally have on with the ignition.

 

I am making a semi educated guess here, I do not have an actual 620 to physically poke around in the wires of. Somebody want to donate me one?

 

I see a "heater" relay on some internet diagrams that I have. This relay might supply power to the heater in the cab of the 620, or it could supply power to the choke heater on the carb. of the motor, or both.

 

I hope this helps you. I am a lot better with 521 electrical issues.

[datzenmike]

Power is supplied directly to one side of the motor by the Blue wire. The other Black motor wire will connect to the solid Yellow wire in first picture and should have a female terminal on it and be plugged onto either of the two coil terminals. (the other end of the Yellow wire goes to the stock switch) The Yellow/Red stripe wire should also have a female connector and be plugged into the other coil terminal and the other end goes to the stock switch. The Black wire in the first picture (with grey wire on the end) comes from the stock switch and should go to ground.

 

In operation, power goes to one side of the motor through the Blue wire. The other, Black is either: connected to ground via the Yellow wire to the stock switch on HI position, OR travels through the coil, and to ground via the Yellow/Red wire to the stock switch in the LOW position.

 

The coil provides resistance and lowers the fan speed. It's mounted inside the blower so it is cooled by the moving air.

[slayer]

well i'll be

 

moparvwfreak you are a god sent ok on that plastic peice where you hooked the two yellow wire there is a arrow i put the black from the fan and the solid yellow wire on the butt end of the arrow and the yellow with red stripe on the other end and i have both speeds...

 

thanks

guys

 

i am sure i will have more questions as my project travels on :)

[moparvwfreak]

no problem. glad to help. i have some other problems i have to deal with but i am more than happy to help if i can.

[fiveNdime]

glad to help, but I didn't do too much