I'm coming to the part of my swap where I'm planning my wiring and starting to get ideas of how I'm going to put it all together. The thought has crossed my mind to eliminate relay 109 and replace it with a standard Bosch style relay. If this is possible it would make replacements much easier to come by. From what I can gather relay 109 is just a purpose built negatively switched relay. Have I missed something?
Swapping relay 109
- Thread starter Ginzzy
- Start date
Tacoma_TDI
Well-known member
I recently just finished simplifying the harness for my Tacoma swap and this is what I did. So long as you maintain the original wiring configuration you shouldn't have any issue. Depending on how many circuits you kept on Relay 109's circuit, you'll want the same size relay to match. In my case, Relay 109 only fed 40A worth of fuses because of how I simplified it so a 40A relay is what I chose with. Here is the electrical box I made for mine, the lone relay on the right on the other side of the fuse box is my "Relay 109". I still need to make the box smaller, excuse the size.
If I recall correctly the stock harness has Relay 109 feeding a significant amount of circuits so make sure you add up all of the fuse ratings properly!! Good luck.
AndyBees
Top Post Dawg
- Joined
- May 27, 2003
- Location
- Southeast Kentucky
- TDI
- Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Yeah, I agree to stay with the 109.
I used the 109 Relay in my set-up and kept the same wiring configuration... no problems. That relay is cheap and readily available.
And, interestingly, the OE set-up from the donor car was screwed up
from the factory. They had accidently flipped the big blue wire with a
small blue wire. I documented the screw-up with photos in my project
build thread. The point is, the smaller wire was able to handle the load
without issue which gives us a base to work from without worry!
I used the 109 Relay in my set-up and kept the same wiring configuration... no problems. That relay is cheap and readily available.
And, interestingly, the OE set-up from the donor car was screwed up
from the factory. They had accidently flipped the big blue wire with a
small blue wire. I documented the screw-up with photos in my project
build thread. The point is, the smaller wire was able to handle the load
without issue which gives us a base to work from without worry!
Excellent I'm glad to hear that it'll work. I was a little concerned about it being a proprietary relay that there might be some other function that it was performing. The heads up about the amperages should definitely be noted. I decided to purchase a 60 amp bosch style relay just to be on the safe side mainly because the pin sizes for the load bearing circuits were similar in size to the stock 109.
Tacoma_TDI
Well-known member
I think Andy is saying stay with the physical OE relay itself, whereas I'm saying you can use an off-the-shelf 4 or 5 pin 12VDC relay. Totally up to you at the end of the day.
The difference between the two relays is this: OE Relay 109 has an internal switching mechanism that when the relay sees power from it's main fuse it switches the relay on without an external pin 85. You can run an aftermarket relay no problem BUT you'll have to integrate a jumper wire from pin 30 (main power in) to pin 85, with pin 86 connected to the ECU T121/18. I chose to do this as it allowed me to fasten the relay inside of the box with only a screw because the OE Relay 109 has no such fastening option.
Andy, would you agree?
Just as a reference, Relay 109 originates from F176 (110A) in the battery fuse box and supplies power to:
1. Glow plugs
2. Heater glow plugs, clutch and brake pedal switches, and crankcase breather heater (F43, 10A)
3. Piston movement & fuel temp sender (F32, 30A)
4. Air mass meter, commence injection valve, EGR valve, anti shudder valve, turbo wastegate solenoid (N75) valve (F34, 10A)
Last edited:
For some reason I didn't see Andy's reply when I made my post and was referencing your post Tacoma_TDI. I think my reason for wanting to switch to a standard relay is for similar reasons to yours. In my application the wiring in the vehicle has basically been completely redone and custom mounting locations have been used. By switching to the standard relay it will also be using the same type of relay that I have used in other applications on the vehicle so I'll only have to carry one type of spare relay.
Tacoma_TDI
Well-known member
Yep. A standard 4 or 5 pin relay works fine, just needs a jumper cable between 30 and 85 with 87 going to your fuses and 86 to ECU.