1991 CQ B3 Delco Climate Control to B4 Manual Climate Control

[cgharibo]

I successfully switched the heater box from B3 auto climate control to B4 manual climate control and all the flaps work well. Now, I need simplest instructions for the wiring to get the blower working followed by the AC before the summer arrives.

Does anyone sell such a plug-and-play harness or point to me to the wiring options?

Thank you!

[RedV6]

Not sure if this helps. I am mid way into installing manual ac from a B4 Cab into a B4 Coupe. This is the ac harness that connects to the dash harness and the heating control, with ac and recirculation buttons.

[johne]

All the wiring options are in the Audi 80, 90, Coupe, Quattro Bentley Official Factory Repair manual if you get hold of a copy.

I'm not aware of a plug and play harness as such but obtaining the loom from a B4 manual climate unit would be the best place to start.

One additional complication you're going to have is that the blower motor in the B3 auto climate is controlled by the climate control box driven though the silver electronic unit in the middle of RedV6's 2nd image.

On the B4 manual, the blower is controlled by the switch positions of the fan speed switch and a resistor pack which sits in the same place as the silver unit on the heater housing. You need that resistor pack/connector/loom as well. Failed resistor packs come up regularly on eBay for next to nothing. In reality the resistors almost never fail, what fails is the silver thermal fuse running alongside them. Replace the thermal fuse and you're good to go.