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Powering Cluster, Pumps and any PWM outputs

Practical Harness Construction - Club Level

Discussion and questions related to the course Practical Harness Construction - Club Level


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It was a good course and I enjoyed watching it for free, however like J.J.Abrams show it has a few unanswered questions that you raised but perhaps I didnt get to the point where some questions were answered.

1. How do you turn on the cluster via the ecu? I can send 1 aux output to the tacho if i find the signal wire on cluster harness, then the ground speed feedback from the speed sensor has to be shared by the ecu and the cluster, then the pressure and temperature gauges. All while we run out of the limited outputs . Not to mention the check engine lights and every other thing is flashing like Christmas tree.

2. There is bare minimum 1 fuel pump in each car and some of them have only power and ground coming to the pump, a specific output from ecu most probably AUX 1 to 4 is used to turn them on, (now what happened where? I use the aux out from ecu, turn on the 87 pin from relay to power that pump? ) What about when there are multiple pumps? Will they all turn on together or can the be turned on in a sequential manner based on the requirements? P.s [sounds like a noob question, but many people will benefit from this me included] when i turn on the ACC switch I usually get a dump of fuel to the rail so I can start the car , I would like to know the science behind it.

3. The much talked PWM modules that control speeds of things, lets say engine fans and water pumps. Is there a source to find them? Using full speed from the start seems like a battery draining and useless thing for the cars, sometimes these german cars have their own controllers to run these things and I would like to just buy these off from the dealers. Lets say I don’t really need fan running full speed at 90 degrees celcius and I dont need fuel pump or water pump to sweat it at idle. (Later I wil ask andre on how to set up via software too

G'day Falah.

Driving the gauge cluster is very application dependent, and it will be up to you to figure that out for your vehicle. Post up the build details though and we will assist where we can.

Yes, you can stage the powering of your fuel pumps and have the ECU kick on a second, of even third pump when required. This is usually configured to be triggered by the engine speed.

To speed control things like fans and water pumps, you need to use a solid state relay. The ECU controls the relay, and the relay delivers the power. It has to be a solid state relay to cope with the switching speeds. Something like this:

https://www.hella.co.nz/en/products/relays-flashers/solid-state-relays/12v-4-pin-solid-state-relay-22a.html

can be a great option.