Wiper Relay 99 mod

General discussion about our beloved Tercel 4WD cars
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NWMO
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Wiper Relay 99 mod

Post by NWMO » Fri Nov 22, 2019 7:37 am

Post by Folian » Sat Jan 27, 2018 2:07 pm

I researched my options last summer and ended up going with the tried and true .99 relay mod.
In short it’s a relay design that’s most famously used in vw’s from the late 90’s but was used in a ton of different makes and models.

Google for 99 relay wiper mod and you will get a ton of sites describing how it works.


I’ll eventually get around to create a build thread for my tercel. And i will outline what needs to be done to include this relay :)
Hey all,

I believe Folian still visits once in a while, but has anyone else tried this relay? Here is a video of how it works, I don't know if it's plug/play on the Tercels or not?

https://www.youtube.com/watch?v=zCHp2Qg_ngI&t=6m47s

TIA,

Chris
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Folian
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Posts: 23
Joined: Fri Jun 03, 2016 1:00 pm
My tercel:: -87 swe t4wd

Re: Wiper Relay 99 mod

Post by Folian » Fri Nov 29, 2019 2:27 pm

Hi NWMO,

I found the images, unfortunately i didn’t find my own wiring diagram. But from the images you should be able to get it figured out .

A few tips:
I have a swedish car, it is different in places, to US cars (not certain about wipers though)
My car never had a relay to begin with, instead the switchwork in the wiperstalk grounds the motor. So i’ve spliced in a relay connector, I put my relay under the steering column right next to the screwed in place connector.

don’t try to use the washer funtion off the relay, the tercel switch is on the negative side off the motor which doesn’t work with the relay.


I have the intermittent setting on the stalk, but it was unused. on the ”switch box’ you will have to resolder some wires as per the images, otherwise it won’t work. My memory is a bit fuzzy, but i believe the additions is the black, the green that goes to the relay.

Even more uncertain: i think i moved a connector bridge inside the ”switch box” to get the circuit. Or if thats what the black wire ”bridge” was for?

I’m not certain but i believe i moved a bracket inside the switch as well to get the correct circuit.

By studying the diagrams and looking inside the switch you’ll figure it out








Hope this gets you going.
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Last edited by Folian on Sun Dec 15, 2019 11:50 am, edited 1 time in total.

Folian
Newbie
Posts: 23
Joined: Fri Jun 03, 2016 1:00 pm
My tercel:: -87 swe t4wd

Re: Wiper Relay 99 mod

Post by Folian » Fri Nov 29, 2019 2:39 pm

I also added one for the rear wiper, which is now always intermittent, with the delay controlled by the standard switch. That one is alot less trick. I added the relay just next to the motor.
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