Auto Climate kinda works but not really.

[Additivewalnut]

91 NA 2+2 manual. Auto climate control doesn't want to switch the vents or temperature, but operates the fan fine. It's stuck blowing ambient air from the center vents. Worth noting that the clock intermittently works, but the radio functions perfectly. Wipers and washer both front and rear all work too.

I've just installed a different auto amp as a hail Mary with no changes. The vent motors make zero noise. No clicks, no whirring, nothing. The control pod works as far as I know. It beeps, selects whatever I tell it to, the car idles up like it expects the AC to be on. It'll do automatic fan control and whatever if I press AUTO, so I don't think it's that.

I go to step 4 (HA-80) and do the trouble code readouts and it says there are no problems, gives me code 50, and doesn't show anything on the open or shorted section of the display. But nothing works except the blower motor, so clearly something is wrong.

The 7.5 amp interior fuse for the AC isn't new but it isn't blown either. I borrowed the passive belt fuse to check; nothing changed. The engine bay 10 amp AC fuse WAS blown, I borrowed the horn fuse; nothing changed. Didn't bother checking the 2 blower motor fuses because it currently works.

I'm stumped. I suppose it's not out of the question that the motors are dead, but it seems unlikely that all 3 would be so dead that they don't even make a clicking noise or anything. Is there a common body ground all the motors share?

[VStar650CL]

From what I can see in the schematics and WD (HA-113), the Auto Amp has two supply fuses, one battery and one ignition. In those circumstances ignition is often the power supply for the logic circuitry and sensors, but the analog power comes from the battery fuse. I'd suggest a $4 test lamp and start by making sure all the fuses in all the boxes have power when they're supposed to. Visual inspection and fuse-swapping tells you zero about that.

[Additivewalnut]

From what I can see in the schematics and WD (HA-113), the Auto Amp has two supply fuses, one battery and one ignition. In those circumstances ignition is often the power supply for the logic circuitry and sensors, but the analog power comes from the battery fuse. I'd suggest a $4 test lamp and start by making sure all the fuses in all the boxes have power when they're supposed to. Visual inspection and fuse-swapping tells you zero about that.

Which fuses? HA-113 references the display not working, which it does. I think I'm misunderstanding something.
I can poke and prod at the fuses, I've got a test light. Just the only ones I see that are named are the 7.5 amp AC and the 2 15 amp blower fuses.

[Additivewalnut]

Is there at all the possibility that the previous owner tried putting the wrong version of the auto amp in? It's a 1991 but the door says 11/90. Could I actually have the old style that's just HI LOW options and this one with the fan control is incorrect?

[VStar650CL]

Is there at all the possibility that the previous owner tried putting the wrong version of the auto amp in? It's a 1991 but the door says 11/90. Could I actually have the old style that's just HI LOW options and this one with the fan control is incorrect?

Does it have a part number on it? If so, you can plug the VIN into NissanPartsDeal.com and it will show you the matching part and (usually) all the supersessions.

To find out fuse numbers and locations can be a nightmare in the old manuals. I'd just check all three boxes with the key on, and if you don't find any fuses blown, check the power connections at the back of the Auto Amp according to the HVAC WD. The motors are all both powered and grounded by the Amp, so if the Amp has power in all the places it should (41 Batt, 40 Ign, 38 Ign through the Blower Relay) and ground where it should (33, 55), then either it has a problem or all four motors are crapped.

[Additivewalnut]

To find out fuse numbers and locations can be a nightmare in the old manuals. I'd just check all three boxes with the key on, and if you don't find any fuses blown, check the power connections at the back of the Auto Amp according to the HVAC WD. The motors are all both powered and grounded by the Amp, so if the Amp has power in all the places it should (41 Batt, 40 Ign, 38 Ign through the Blower Relay) and ground where it should (33, 55), then either it has a problem or all four motors are crapped.

Welp. I went and probed everything and it's working as intended.... Motors are dead. I don't want to pull the dash