Location of 1994 Sentra Heater Blower Relay

[95_Max_Wreck]

Hi guys, longtime Maxima driver, first time form poster, at least on this site. My 95 Maxima has 316,000 miles, I lovingly fix everything that breaks, and it still drives like new. But this post is about my friend's 1994 Nissan Sentra SE.

I'm trying to find the location of the heater blower motor relay. I know the motor is bad. I pulled it out and tested it directly with 12 V. If you manually spin it, it will start up but gradually slow down and stop. It draws way too much current. But before you spin it it shows as open. There is no voltage at the resistor block, there is no voltage at the multispeed switch, but the fuses are good. There is evidence of overheating/melting at both the motor plug and at the multispeed switch.

Not being familiar with the electrical system in this car, I can only assume that there is a relay that is open. But I can't seem to find anything that tells me it's location. Unfortunately, the 1994 Nissan Sentra foldout.pdf (available on this website) defaults to the 1993 240SX diagram. Surely these aren't interchangeable? So I can't trace the schematic to find out if there's even a relay in the line. But I assume there is.

Any help?

[centralcoaster33]

Thank you for pointing out the wiring diagram foldout. I think that could be a mistake. I did look to the EL chapter and do see the wire harness and blower motor connector plug M63. I did not spend time tracing it to components for your friend. I did see relay box information, but didn't notice one specific to AC / heater. So, I'd guess it's on the accessories relay. That's just a guess. You could look further into the FSM. Apparently, only the foldout link is bad.

Welcome to NicoClub. Let us know if we can help more.

[95_Max_Wreck]

OK, I will check the related parts of the manual.

And thanks to the forum mods for posting the manuals. I had to buy the one for my Maxima.

[centralcoaster33]

I've always felt the FSM should be included with a car. Cars are already expensive to buy new. They might as well throw the manual in there... or a CD or USB stick nowadays.

[95_Max_Wreck]

^^ Indeed...I agree.

But I have updated information on the 1994 Sentra with the manual heater control panel, not the "push control" panel.

There is no relay in the power circuit. Since power actually flows from the negative to the positive, Nissan designed the circuit according to that, which is opposite of what other designers might do.

From the dual 15 amp fuses, the power goes directly to the fan motor, from there to the resistor pack, and from the resistor back to the speed control switch, then to ground. With the motor unplugged, there will be no voltage anywhere on the circuit. And there is nothing in between the fuses and the fan motor but a wire with a 30 amp capacity.

So the motor on this car obviously had a shorted armature, drew too much current and blew out the Speed 1 resistor circuit, which makes sense because that's the highest resistance in the pack. So are replace the motor and the resistor pack from a junkyard, and the system works like brand-new.

By the way, the HA section of the service manual told me what I needed to know in order to trace that circuit.