hope this is in the right forum section

While sitting browsing here earlier and seeing people always asking for the honda demister wiring / relays / switches etc I thought this might be of help to some people.

I spent a good while searching the forum and pieced together various odds and ends on how to do this but no definitive guide.. so hopefully this will help

I recently wired this in my MY99 JDM which has been retro fitted with what appears to be a genuine honda roof from an 06 car going by the info I had.

I have yet to wire the rear soft top screen, as I have had the hard top on all winter, but the principle is the same

***I AM NOT RESPONSIBLE FOR YOUR OWN INSTALLATION AND ANY DAMAGE CAUSED AS A RESULT OF FOLLOWING OF THIS GUIDE, THIS IS HOW I FITTED MINE AND I AM SIMPLY SHARING THE INFORMATION WITH PEOPLE***

You will need (all available in Halfords / Maplin / eBay / Motor Factors)

1x Illuminated Switch (your choice)
1x 4 or 5 pin 12v changeover relay

3m of cable, colour isnt massively important, I used RED (i used 12gauge, 10 or 12 should be fine)

Electrical Terminals - I used 7x insulated spade connectors for the relay terminals, and switch, then male/female connectors for the hardtop wiring release.

2 fuse holders, and 2 fuses (15amp)

Tools :

Voltmeter
Screw Driver
Wire Strippers
Wire Crimpers
Soldering Iron
Solder
Zip Ties


ok, I firstly fitted my switch in the blank below the speedo, just above where the keys go in (theres one in either side for various things, you can put the switch wherever you like)

The switch had 3 clearly marked terminals :

POWER IN
POWER OUT
EARTH

Using my voltmeter I tested the wires coming off the ignition barrel, and from memory the BLACK/YELLOW was the ignition source wire. I soldered a length of wire from this BLACK/YELLOW wire and connected it to the POWER IN on the switch. I inserted a fuse holder and 15amp fuse inline between the ignition wire and the switch for safety. I also took a length of wire from the EARTH terminal on the switch and put it to a chassis earth (drivers kick panel, or say at the radio wiring is fine)

From the POWER OUT Terminal i ran a length of wire to TERMINAL 86 of the 4 or 5 Pin RELAY, The opposite terminal, TERMINAL 85 was then also wired to a chassis earth (you can use the same earth as you used for the switch)

Essentially now the relay has a switchable power source, this can be tested by putting the ignition on and operating the switch, the relay should "click" when the switch is turned on and off, and also the LED on the switch should illuminate

Next you need to put your power source that will power the rear window to the relay. To do this I again measured the voltage on the WHITE wire at the ignition barrel, this wire is 12V CONSTANT and again I fitted and inline fuse holder with 15amp fuse in the length of wire between the WHITE wire and TERMINAL 87 on the 4 or 5 pin relay.

With this now connected this leaves TERMINAL 30 on the relay the only free terminal (ignore 87a if you bought a 5 pin relay). from this terminal you want to run a length of wire from the relay to the rear of the vehicle where the OEM rear window demister wiring would be. For me this is behind the passenger seat on a RHD car.

I removed the panel behind the passenger seat to allow me better access to run the cable.

My hard top has a grey 2 pin plug on a curly "phone" style cable which is clearly the wiring for the OEM demister.

I then carefully pulled off the plastic trim panel on the side of the hardtop, this revealed the black curly cable going up and one wire connecting to the rear window, and the 2nd wire connecting the to chassis of the hardtop.

The wire that is going to the window is what gets connected to the wire you have just ran from TERMINAL 30 of your relay, from memory this is BROWN, but please remove the panel to double check.

again from memory the remaining wire is BLACK and is to go to earth, I used a small section of wire and chassis earthed this to a screw behind the passenger seat panel, this then allows me to have both the 12v feed from the relay and the earth on connectors to remove the roof with ease.

Using the male / female terminals I then crimped each wire, this allows me to safely remove the wiring when I remove the hardtop.

Once complete build up, using ZIP TIES secure any cables and the relay, sit back and enjoy!

I will update this with pictures ASAP, I decided to do this off the cuff and have no pictures.

I`m not really one for leaving my rear window on all the time, I use it sparingly and always turn it off once it has sufficiently cleared.

I dont know what effect leaving it on constantly would have as the method I have devised is not thermostat or temperature controlled to cut off. I have been using this for several months now and its a complete godsend being able to see out the back of my car on cold mornings!!!!

I hope this helps people who are struggling with finding the OEM honda wiring, or who simply dont want to spend 3 fortunes.

And anyone please feel free to add to this, any additional info is more than welcomed

 

what specific relay did you use? maplin part number? why didnt you wire the screen to an ignition switched 12v instead of a constant? with the constant you could accidently leave it on and drain you battery...

oh, and pics would be a massive help!

 

Better late than never I guess.

The relay is just a regular 4 or 5 pin changeover relay. I'll see if I can hunt out the part.

The relay is wired using an ignition source, the power source feed passing through the relay is constant.

There is no risk to leaving the window turned on with the keys out