87 2+2 NA with digital cockpit.

Climate control system not working. The head unit acts normally (displaying status changes as you press the different buttons), but the fan will not kick in.

Prior to this, whatever controls the air direction to the dash vents stopped working. That problem happened, and later on the whole system became unresponsive.

The manual defrost works, thus indicating no prob with the fan.

Checked fuses & relays, all ok.

I have a second head unit that I swapped in, same behaviour. So I assume the units are ok.

I've done the "wiggle test" of every wire/connector I can get my hands on, checking for a loose connection. Nothing found.

Ideas?

Thanks.

Joe

 

first thing to do is get your vacuum hoses replaced. hvac needs vacuum to work. After that may be one of the sensors need replacing.

 

I unplugged the fan motor and measured voltage at the plug between + and - of the plug itself.

With manual defrost, I get expected results of 14 volts.

When I switch to climate control (Auto/Econ... the AC is long ago dead, so I'm just looking for old school fan operation), voltage shuts down. Except it's not the + , the ground is being disabled. I confirmed that by jumping from the + of the plug to a body ground, and I see my 14 volts again. When I turn my climate control on, I get 14 volts, turn off , 0 volts, with plug jumpered to body ground.

So, the head unit is sending 14 volts to the plug in Auto/Econ mode, but something is shutting down ground.

Looking at wiring schematic, I see the ground of the fan goes back through the fan control amplifier ( part# 27266-01P01 ), I think. It also looks like the manual defrost bypasses this unit.

I'm thinking this might be the issue. That's as far as I got today. Thinking I could do a little temporary rewire for a body ground for the fan and see what happens.

Anyone ever have an issue with the fan control amp?

 

Highly likely that is the issue... https://z31performance.com/forum/z31...oblem-in-z31-s