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As the title says, I want to swap in HVAC controls off my old 1990 NA into my 2001. This is the opposite direction most people want to go. I've had the NA6 dash in the car since 2017, and back then I just I slotted the NB climate controls in place of the radio on the NA dash. The Bose system in the NB was trash and had no FM reception, a broken CD player, and I hated the rest of the NB tan interior. So I swapped in the dash and deleted the sound system. Now 5 years later, I want a radio again and it's time to finish this.
I've figured out the wiring for the fan speeds, and the back lighting will be easy as well. That was an easy re-pin job. Where I'm less able to make sense of things is the AC trigger wires. I'm having difficulty interpreting the electrical function of the various circuits that share grounds and power feeds. Will I need to install diodes as people going NA -> NB have to do? Are these only to make NB features work with NA wiring? Will I need to remove or flip diodes in the NA HVAC controls?
I'll refer back to a diagram from m.net for continuity with other information on the web. The perspective of the diagram is looking into the chassis/dash side connections.
Here is my understanding of the NA and NB wiring pinouts. I am not saying the "Function" column is correct, just my understanding.
The NA only has provisions for the large 8 wire connector to control all HVAC functions, and a separate 2 wire connection for backlighting.
The NB2 moves the backlighting connections to the large connector, and adds separate connectors for the AC switch, rear window defroster, and the feature that forces the AC on when the windshield defrost mode is selected. I do not have a rear window defroster on any top I own. I do not want the AC and defrost settings tied together. The loss of these two features doesn't matter to me.
Here is how I have things set now:
Result: All fan speeds function as normal, but the AC does not work. When I push the AC button and turn on the blower fan, the AC light comes on in the HVAC panel, but the AC clutch does not engage.
I have a spare NA climate control panel I can hack up for testing.
OP is an absolute moron. The AC thermoswitch behind the dash was not plugged in. With that plugged in, the AC system works properly. The AC compressor comes on when the AC button is pressed and fan set to any speed.
But I am 95% confident the NA wiring harness diagram is wrong based on visual inspection and multimeter testing. Below you can see how the diodes actually are oriented - the way the linked diagram shows would never work. The P3 and P4 wires are seeking ground through the fan switch. If the diagram in the linked 1990 service manual was correct, they would be blocked from ever going to ground through the fan switch.
The switch panel works unmodified, with the NB wires repinned in the following arrangement.
I don't know what the function of wire P5 is on the NA, but I don't see a need for it in this use case. Given that it is only on the higher fan speeds, I am guessing it is a switch that triggers some additional idle compensation on the antiquated NA6 ECU. That slot remains empty for my use. The lighting wires are on a separate connector that I have removed from the diagram for clarity.
Last edited by OptionXIII; 04-12-2023 at 11:24 AM.
The diagram posted above is edited by me. Below is how it appears in the linked 1990 manual.
If the diode closest to the "A/C SW" was in the orientation shown above, the two wires below it BLU and GRN-RED would never be able to ground through the fan switch.
I do suck at electricity but I want to post correct diagrams and data. If I have this messed up, I'll delete it and hide my ignorance in shame.
02-23-2022, 06:16 PM
NA climate control swap into NB
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