'86 Nissan 720 heater problem

[Livengood13]

Not really familiar with the heater problems. Anyway when the switch is on or off it doesnt come on at all. i have replaced the blower motor and still nothing. resistor has been changed and nothing. Anything that I might need to know?

[SHORTDOG]

Check the fuse.

[wayno]

There is a relay, a fuse, a plug, resister, and a ground.

Check the fuse, I assume since you have had the blower motor out, that you what I would call cycled the plug, there is a big ground on the upper firewall in the cab that needs to be tight, and then there is the resister, that is the white thing with all the blue wires going to it under the glove box.

Do the easy things first, fuse, resister, relay, and then search for the ground which will likely require pulling part of the dash out.

If you have A/C, then things might be in different places.

[datzenmike]

Not really familiar with the heater problems. Anyway when the switch is on or off it doesnt come on at all. i have replaced the blower motor and still nothing. resistor has been changed and nothing. Anything that I might need to know?

 

Won't be on in the off position. Unless you replace those parts with ones from Nissan, you probably put in inferior parts. I hope you didn't throw the old ones away.

 

The tenth fuse over from the left side is the heater fan fuse... 20 amps. This only powers the blower motor when the heater relay is ON. The heater relay should only be ON with the ignition in the ON or the ACCESSORY position. The power to turn the heater relay ON  from the ignition switch passes through the sixth fuse from the left side, but if your windshield wipers work it must be good.

 

 

 

If all the above checks out you should have power to the Red/Yellow wire on the fan motor. (ignition on) The Blue wire goes to ground or through the resistors to give variable speed fan operation. If you ground the Blue wire at the motor, you should have high fan speed. If it does, but the switch does not work, then the ground wire (Black) must not be grounded or the plug not working..

[wayno]

Won't be on in the off position. Unless you replace those parts with ones from Nissan, you probably put in inferior parts. I hope you didn't throw the old ones away.

 

The tenth fuse over from the left side is the heater fan fuse... 20 amps. This only powers the blower motor when the heater relay is ON. The heater relay should only be ON with the ignition in the ON or the ACCESSORY position. The power to turn the heater relay ON  from the ignition switch passes through the sixth fuse from the left side, but if your windshield wipers work it must be good.

 

 

 

If all the above checks out you should have power to the Red/Yellow wire on the fan motor. (ignition on) The Blue wire goes to ground or through the resistors to give variable speed fan operation. If you ground the Blue wire at the motor, you should have high fan speed. If it does, but the switch does not work, then the ground wire (Black) must not be grounded or the plug not working..

That's the issue I am having, if I ground out the blue wire my fan works, but I am to lazy to remove the dash to fix the ground.

[Charlie69]

Run a new tempory ground. until you a have another reason to pull the dash.

[moalaska]

On 11/13/2014 at 4:27 PM, datzenmike said:

 

Won't be on in the off position. Unless you replace those parts with ones from Nissan, you probably put in inferior parts. I hope you didn't throw the old ones away.

 

The tenth fuse over from the left side is the heater fan fuse... 20 amps. This only powers the blower motor when the heater relay is ON. The heater relay should only be ON with the ignition in the ON or the ACCESSORY position. The power to turn the heater relay ON  from the ignition switch passes through the sixth fuse from the left side, but if your windshield wipers work it must be good.

 

 

 

If all the above checks out you should have power to the Red/Yellow wire on the fan motor. (ignition on) The Blue wire goes to ground or through the resistors to give variable speed fan operation. If you ground the Blue wire at the motor, you should have high fan speed. If it does, but the switch does not work, then the ground wire (Black) must not be grounded or the plug not working..

Where is this black wire?  

[datzenmike]

, below the ash tray.

 

Black wire is probably on the fan speed control 

[wayno]

The black ground wire is buried deep behind the dash and heater ducting, it's nearly impossible to get to without removing the dash.

If you want to get your heater fan going ground the blue wire out to see if it works(see photo below, ground the female end), if it works then put a toggle switch between the blue wire and ground so you can turn the fan on and off like in the second photo, that wire grounded out on the plastic console is grounding out to the console mount metal bracket holding the console in position.

 

 

[moalaska]

22 minutes ago, wayno said:

The black ground wire is buried deep behind the dash and heater ducting, it's nearly impossible to get to without removing the dash.

If you want to get your heater fan going ground the blue wire out to see if it works(see photo below, ground the female end), if it works then put a toggle switch between the blue wire and ground so you can turn the fan on and off like in the second photo, that wire grounded out on the plastic console is grounding out to the console mount metal bracket holding the console in position.

 

 

I already have it macguyvered like this, I'm trying to restore functionally of variable speed control so it's not going full blast.  Fan at full current draws a good amount of amps, and when I got the fan, headlights, other accessories going and trying to run a snow plow, it maxes out my electrical system.  So is there an easier way to ground out the fan speed control or whatever.

[wayno]

I don't know what to say for sure, you could try putting one of them vampire clips/splice clips onto the black wire on the fan control switch and ground out that wire to a good known ground, that is the only ground I see in that circuit except for the one at the heater relay.

[datzenmike]

Try working the switch though its range. This will clean the contacts. I can't see wires not working. Did you place a ground on the fan motor to make sure it's running??????? It's the BLUE one going to the motor below.

 

[moalaska]

54 minutes ago, datzenmike said:

Try working the switch though its range. This will clean the contacts. I can't see wires not working. Did you place a ground on the fan motor to make sure it's running??????? It's the BLUE one going to the motor below.

 

Yes blue wire grounded turns fan on.

[datzenmike]

Then we now know for sure that the motor is good.

 

Time to take the fan speed switch out of the dash and mess with it.

[MaddieCycle]

I've got 12v at the red/yellow wire going to the blower motor, and the motor does not turn on when I ground the blue wire.  Assuming this means time for a new blower motor.

[Lockleaf]

Likely yes.  Next easy step is to pull the motor and before getting a new one, put 12v directly to the motor and see if it runs.  If it won't run hooked straight to 12v then its dead and go from there.

[bottomwatcher]

On 4/5/2021 at 9:04 PM, MaddieCycle said:

I've got 12v at the red/yellow wire going to the blower motor, and the motor does not turn on when I ground the blue wire.  Assuming this means time for a new blower motor.

If it doesn't work pull it apart you have nothing to lose. It just may be a broken brush wire or stuck brush or just dirty. If it can't be fixed at least you know what it looks like on the inside.

[datzenmike]

Wire it and tap with a hammer.

[MaddieCycle]

On 4/7/2021 at 7:32 PM, bottomwatcher said:

If it doesn't work pull it apart you have nothing to lose. It just may be a broken brush wire or stuck brush or just dirty. If it can't be fixed at least you know what it looks like on the inside.

Motor was cooked. I got a new motor for $50 from O'Reilly, the box it came in was very dusty and it said "Made In Canada".  Spare parts probably haven't been made in Canada for decades. This is probably new old stock spare parts from a different (and better) era.