Connecting Aux to Climate Control Buttons Pictorial

Sometimes you can get lucky if your car has a (-) trigger wire for the rear defogger, heated seats, etc. But what about other features which don't have a trigger wire? I'll show you how to tie into the momentary switch of your climate control... I will be controlling the front window defogger using an AUX channel of my remote starter via a relay. Here's my climate control (2000 Maxima) taken apart. There's the on/off button for the front window defogger. Here's the back of the circuit. The contacts of the button are circled. MAKE SURE TO TEST THE CONTACTS USING DMM. It should read no-continuity normally, and close to 0 ohms while button is pressed. Solder some thin (22-24 gauge) wire onto the contacts. To avoid a poor solder joint, be sure the wires don't move even a fraction while the solder is cooling; I used some "helping hands" to keep them steady. I used hot glue to secure the wires (prevent strain & vibration on the solder joints). Rather than using a large Bosch style relay, I'm using a mini circuit board relay to avoid the unnecessary bulk. Everything is secured using hot glue. I put a mini-connector to make removal of the HVAC control unit easier. Here's the final look.

Wiring a Bosch style automotive relay like so: 87 - switch contact 1 30 - switch contact 2 85 - Negative AUX trigger 86 - +12V constant (fused)

Great info!    Another good use for those mini-relays.  Even had a coil quenching diode added ( Howard would be very happy ).  

There would definitely be an extra charge for that install upgrade.

Soldering is fun!

much easier to grab the wire at the SECU where your locks/door pins/faa/fad are. GREEN/ red (-)Ted

2nd Year Tier 1 Medical School

Still installing as a hobby...pays for groceries

Compustar Expert

kreg357 wrote: Great info! Another good use for those mini-relays. Even had a coil quenching diode added ( Howard would be very happy ). There would definitely be an extra charge for that install upgrade.

I love the mini relays for low current stuff. It is time consuming (and potentially risky), so not really an option for 99% of customers... It is nice to have on my own car.

tedmond wrote: much easier to grab the wire at the SECU where your locks/door pins/faa/fad are. GREEN/ red (-)

Hi tedmond, the GREEN/ red @ SECU is for the rear defroster...and yes, I connected that as well

Howard has just seen this and likes every part, full marks to you Mr. Cake

Just seen your original post, brilliant, you've gone where no man has gone before, except maybe Kreg, Ted and myself, superb attention to detail.

Thank you Howard! I still remember the (not too long ago) days when you among others, were helping to answer my amateur questions!