Engine On Signal Via Ford Transit Vehicle Interface Connector
Our house batteries can be charged via 2 sources, the 270 W solar panel on our roof or via the vehicle’s electrical system. When charging via the vehicle’s electrical system we didn’t want to accidentally discharge the starter batteries to the point that the van wouldn’t start. We needed a way to turn off the house battery charging circuit when the engine was off. We also wanted the ability to use one of the upfitter switches to manually disable charging even if the engine was on. To accomplish this we needed a positive switched engine on signal.
Parts
- SPDT 12V Relay – $14
- In-Line Fuse Holder – $7
- Pigtail connector 3U2Z-14S411-JBA – $45
- Various Crimp Terminal Connectors – $17
- Electrical Tape – $8
Instructions
Most vehicles come with some type of engine on signal, I believe on the Sprinter it’s the D+ signal. The Ford Transit also comes with an engine on signal called the Vehicle Interface Connector, or C33-E, but it’s not a positive signal nor is controlled by the upfitter switches.
Vehicle Interface Connector C33-E
The Vehicle Interface Connector is available on all Transit models and provides the following signals: left turn, right turn, engine run, vehicle speed, switch illumination, and ignition. It is located under the driver’s seat near the front of the seat pedestal closer to the center console area. You must take off the front seat to get to the connector.
The Vehicle Interface Connector C33-E provides 6 signals.
Pin 3 on C33-E becomes an active ground when the engine is on but it will only sink a max of 250 mA. The signal is not active when the key is in Off (position 0), Accessories (position 1), Run but Engine Off (position 2), or Crank (position 3). But with the use of a normally open relay you can get a positive engine on signal that is controlled via an upfitter switch.
The house batteries are only charged by the vehicle electrical system when the engine is on and the upfitter switch is on.
To connect to the Vehicle Interface Connector C33-E I purchased a mating pigtail connector part number 3U2Z-14S411-JBA. Pin 3, engine on, coming out of the pigtail connector is then connected to pin 85 on the relay. Pins 86 and 30 on the relay are connected to an upfitter switch via a inline fuse. The output of the relay, pin 87, is now a positive engine on signal that can now be controlled via an upfitter switch and will always be off if the engine is off.
In a future blog article I will show how we are using this new signal to control the charging of our house electrical system.
I have been trying to figure out how to wire a battery isolator so it activates only when the van is running. I think this could be the solution and it’s location is nearly perfect. My Transit is a 150 base so I doubt I have the wiring for the uplifter switches but maybe that is ok. I plan on building a box to go behind the seat with a deep cycle battery and inverter. Once I have figured that out I want to add shore power to charge both batteries.
Heath, did you figure out how to do it? I’m planning to get a house battery and isolator. I also need to connect the isolator to a 12v trigger. If I read it right we have to buy the pigtail connector 3U2Z-14S411-JBA.
Yes, I bought the part Part No.: 3U2Z-14S411-JBB from Fordpartsgiant.com. I used a multimeter to identify the correct pin and it works great. I have not gone on to set up shore power yet. I connected straight to the battery nad built a box that has my house battery, isolator, and fuses. One tip is to buy the flexible cable. It is so much easier to work with.
Heath
Thanks. I saw online that a 2nd battery will fit next to the stock battery if you remove the battery box.im planning to do this.
First of all, thanks a lot for all the info you give here and on the ford transit forum !
I’m in the process of installing a battery combiner, a Victron Cyrix, and like you I’d like the batteries only to be combined when the engine is running AND when a switch allows it to.
The Cyrix is a very simple unit : you plug the + from both batteries to the Cyrix, then plug a ground so the internal electronics can do their magic.
My plan was to put the switch on the ground wire (low amps). Originally I was planning on using a relay, powered by a “engine-running-only 12V” to close the ground wire but do I really need that ? Do you think I could directly plug my ground wire from the Cyrix to PIN 3 of the C33-E ? (with a switch halfway so I can turn it off even with engine running if I want to). Then if I understand correctly my Cyrix would only be grounded when engine’s running.
Thanks !
Ben
I would take a look at the data sheets, https://www.victronenergy.com/battery-isolators-and-combiners/cyrix-battery-combiners. They show examples with switches.
the switch they show there is for the start assist (in case car battery is dead). But I know I can have a switch on the negative wire of the Cyrix, Victron confirmed that.
Question is : is it wise to connect the ground wire of the Cyrix to Pin 3 of the C33-E so the “loop” can only be closed when engine is running.
I would use a relay to keep the 2 systems isolated.
Thanks for this writeup! Thanks to it, I managed to hook up a SPST relay to our Transit’s rear 12V aux port and have it switch on only when the engine is running. Normally, the 12V aux ports are on the 30 minute timer circuit that keeps them on, even after the engine has been shut down. That’s great for small low current accessories if you want them to keep running for a bit while parked, but we were worried about draining our Transit’s starter battery since on this rear aux plug, we have a 12V DC charger supplying 120W to our Goal Zero 1400 lithium battery. That sounds like one way to drain a starter battery.
With the relay switching off when the engine shuts off, we can now leave the 120W Goal Zero charger plugged in, since it will only draw power while the engine is running. Perfect!
What gauge wire did you use for the Engine Run output (from Pin 87 to the destination)? I bought the relays you linked (thanks!), which have 16 AWG pigtails. I was thinking of using 16 AWG for the balance of the wiring. In my case, I’m running the signal to a Renogy 20A DC-to-DC charger located about 6 feet away (12-ft. circuit).
This is great stuff! I have a 2018 Transit and just need to search for this interface. I am debating if I really need to put it to a switch? Why did you choose to do so? Doesnt the relay automatically ensure that the vehicle battery doesnt run out of power? When does a switch come in handy for you?
Sometimes I don’t want to charge the batteries while the engine is on, the upfitter switch allows me to be in control of that. The main reason is that the inverter/charger sits right behind the driver’s seat and has a loud fan, the switch allows me to turn it off.
Hi Matt,
thank you! As i dont have a free AUX switch I am building one into the side of the driver seat directly. Others put the + of the starter battery on pin 30 and the active ground on pin 86. If i understand correctly your switch turns the relais on/off. Can I achieve the same buy stopping one input signal (e.g. the active ground), i.e. can I also put the switch in between the active ground and the relais?
We have found that there is not enough current between ignition line and engine-on signal to close the relay 🙁 Any one else had this and solved it?