electrical query - bench testing components

Hey guys - I'll admit I'm a bit novice when it comes to electrical - but learning...

I have the Wilwood Electric Parking Brake and I'd like to bench test to ensure it's working properly before I get into final mounting locations

I have the rear EPB calipers mounted with the clamping servos on the rear brakes and wired up, the switch is crimped to test, and I have a 12V benchtop battery for power (tested at 12.71v)
I've also tried the regular car battery (tested as well)

assumptions:
BATTERY (+) means connect to the (+) on the batter (duh)
GROUND (-) is (-) battery
ACC or IGNITION ON is specifically stated not to connect directly to the battery but a switched 12V

here's the Wilwood schematic
https://i.imgur.com/IpcKP3f.png?1

we put one of the 2-blade on/off switches in the circuit (like below) - but I'm not sure how to run the (-) line back to the battery, assuming the EPB takes care of this through it's own GND (-) line
https://i.imgur.com/ofNxr4e.png?1

without ACC connected we get 12V - but the unit will not power up (assuming the ACC is a momentary trigger)
with the ACC connected through the switch, we only get 3V (not enough to trigger IMHO)

any ideas? I'll reach out to Wilwood as well, but I thought maybe my learning can help others on here too!!

So the On/Off toggle switch to Wilwood EPB ECU connection (red wire in your circuit diagram) is for the ACC connection in the Wilwood wiring diagram, right?

What point in the circuit are you measuring 12V & then 3V?

And I would say you are correct that the return circuit to the ECU is taken care of as long as the black (ground-) wire is connected to the negative battery terminal.

Earl

The way I'm reading that diagram is that the Battery + and - connections at the top of the diagram are the main power source for the ECU and the motors (hence the 40A fuse). The "ACC or Ignition On" wire is simply a trigger so that the system will only work when the ignition is in the accessory or on position. The warning to not run it directly to the battery is so that the EPB will not be operational when the car is powered off (ignition key is in the off position). For the purposes of testing, I think you can just jumper that lead to the battery + for now. It's just looking for a +12V signal on that lead to "wake up" the system.

As JohnK said, the 12v switched is likely triggering a relay internal to the control box. To test the unit, both the main battery power and the 12v switched power need to be present for the relay to send power to the device controlled by the relay.

Quote:

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Originally Posted by narly1

So the On/Off toggle switch to Wilwood EPB ECU connection (red wire in your circuit diagram) is for the ACC connection in the Wilwood wiring diagram, right?

What point in the circuit are you measuring 12V & then 3V?
And I would say you are correct that the return circuit to the ECU is taken care of as long as the black (ground-) wire is connected to the negative battery terminal.
Earl

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yes the leftmost red wire (oops had them both red) in my diagram is the one pointing to the ACC red wire with 5A fuse

measuring 3V on the outlet from the switch, just using aligator clips right now

oh and I've tried direct connecting both BATTERY and ACC to the positive post, but no dice... maybe bad ECU?

I guess that's possible but I'd check the simple stuff first. Every time I jump to a complicated solution (bad ECU) it turns out to be something ridiculously simple. Check that you have good + and - connections to the battery, and check that both the 5A and 40A fuses are not blown and are seated properly in their fuse holders?

Quote:

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Originally Posted by JohnK

I guess that's possible but I'd check the simple stuff first. Every time I jump to a complicated solution (bad ECU) it turns out to be something ridiculously simple. Check that you have good + and - connections to the battery, and check that both the 5A and 40A fuses are not blown and are seated properly in their fuse holders?

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yeah - both fuses are good and have pulled/reseated them, and the benchtop battery has screw down terminals so everything is super solid on connection...

12V is 12V right? I mean it's a small desktop battery?
I don't this CCA matters in this point, it's not cranking over an engine - but maybe I'm wrong? I think the 3V issue is odd... and would make sense as to why it wouldn't trigger a 12V ECU switch... just wondering where the other 9V are going :)

It's not rocket science LOL. It's only a switch. If you measure 12V going in you should have 12V coming out when it's in the on position. Check for that first without having it connected to the ECU ACC connection, then with. If you are reading 12 V then 3V respectively then you either have a poor connection between the switch/fuseholder/battery +ve or a weak battery (assuming the ground -ve connections are good...

A small desktop battery is most likely not going to have the amperage to power something that's protected by a 40A fuse. I'd use the car battery to test.

Edit: If I'm understanding correctly, you've added a SPST toggle on the ACC lead in addition to the Wilwood dash switch that's elsewhere in the harness? I would ditch the toggle switch. Not needed for testing. Just jumper both +12V leads to the battery + and then use the Wilwood dash switch to actuate the brakes.

interesting, just re-checked the Wilwood site and looks like there are newer directions... well, at least colored, but shows the switch in this one
I've also tried running the ground wire right onto the frame as well...

https://i.imgur.com/Ju3QDxg.png?1

Quote:

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Originally Posted by JohnK

A small desktop battery is most likely not going to have the amperage to power something that's protected by a 40A fuse. I'd use the car battery to test.

Edit: If I'm understanding correctly, you've added a SPST toggle on the ACC lead in addition to the Wilwood dash switch that's elsewhere in the harness? I would ditch the toggle switch. Not needed for testing. Just jumper both +12V leads to the battery + and then use the Wilwood dash switch to actuate the brakes.

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my son and I also tried connecting directly to the Type51 battery as well...

Hmmm, OK... seems like you've got all the basics covered. Maybe try giving Wilwood a call and see what they have to say.

Did not read all the suggestions, but a 3 volt reading sounds like the voltage is going through an indicator light, or the ground is being feed through a light.

Quote:

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Originally Posted by Railroad

Did not read all the suggestions, but a 3 volt reading sounds like the voltage is going through an indicator light, or the ground is being feed through a light.

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yeah sadly there's no light or anything else connected other than the battery and the lines going to the ECU and switch for ACC...

success!!!!

https://youtu.be/DGxz_LXkc18

Awesome! Glad you got it working. That's a pretty slick setup.

Thank you!!! We thought we were going crazy!! ��


So thankful for all the support here!!!

Thanks for sharing the info. It's builders like yourself and many others posting their findings, links, product info, and installation tips that make my planning phase stay active and fun.

Quote:

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Originally Posted by toadster

success!!!!

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So what ended up being the problem?

Inquiring minds want to know, LOL.

I like that setup. Maybe on my next build...

I have those on my car. Very happy with it, tremendous holding force. Wired it up through the transmission reverse lockout circuit, now I can set max speed of engagement. This just in case someone decides to try the switch at speed...Had to switch sides for the calipers, other that that a tight but easy install.

Quote:

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Originally Posted by narly1

So what ended up being the problem?

Inquiring minds want to know, LOL.

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honestly I think we really needed the big battery and we put the terminals on the battery and tightened the connections pretty well, I believe we weren't getting full contact, or we werent' getting enough amperage to allow the circuit to drain properly
one big note in the directions is that you need a solid ground location since all the EPB motor amperage will flow to the ground