I'm having a very weird problem with my Haltech Elite install in my FB and can't figure out what's happening. The clutch switch is on an SPI.

When I push the clutch pedal in, the battery voltage drops significantly. Dash lights go dim (same circuit as the clutch switch), and the Haltech shows a voltage drop from ~12 to ~10 volts. It jumps right back to 12v and lights go back to normal as soon as I let off the pedal. In fact when I was first testing this I blew a fuse as soon as I pushed the pedal in, but I swapped in a 20 amp spare fuse (originally 15 amp) and it hasn't blown since.

I de-pinned the clutch wire right in front of the ecm, and the voltage drop goes away when depressing the clutch. I also put a multimeter on it while de-pinned and got a 0v and 12v reading, and no battery voltage drop. This makes me think the Haltech's SPI is causing a weird voltage drain but I am stumped.

SPI is configured this way:
Input Mode: Digital-Switched
Edge Select: Falling
Sensor Type: Hall Effect
Pull up: disabled

 

Whatever you’re doing, stop. Sounds like a situation that can easily damage the ecu.

How do you have it wired? It’s a simple single pole, single throw switch. Connect one side to chassis or ecu signal ground and the other side to the SPI. Enable the pull up. It should be about as simple as can be.

 

I think I misunderstood how the SPI needs to be wired. I reused as much in-dash factory wiring as possible, and in this case there is a connector in the body harness X-07 which contains the output of the clutch switch. I made my haltech harness plug right into this X-07 connector, with the SPI1 input wire connected to the single clutch switch wire which has either 0 or 12 volts, just like the factory ECM's input 'i' in the diagram. Below is the wiring diagram illustrating this with my annotations.

It sounds like I need to get rid of the power input side of the clutch switch and connect it to a ground instead, which will require some in-dash wiring.

 

(double post)

 

The SPI is 12v tolerant. From what I can see in the schematic it should work the way you have it wired. I would pull the SPI terminal out of the ECU, make sure it’s not going to short to ground, and check voltage on that terminal with the clutch in and out. Let us know what you find.

 

I tested tonight with a multimeter at both the x-07 connector and at the Haltech ECM input (connectors unplugged). This was pin B8 for me with the Elite 1000. On both, I got 0v with the pedal idle and 11.3v with the pedal depressed, and no voltage drop whatsoever at the battery like I got with the Haltech hooked up. Based on this, I don't think I have a short anywhere in the harness.

Is it possible that I damaged the Haltech when I first powered it on with the clutch set to a 5v pull-up? I hope not but want to point it out. Immediately after that I disabled the 5v pull-up.

For reference, the ECM 12v trigger is coming from an interior circuit through the x-07 connector but on a separate fuse from the clutch switch. The 3 positive wires in the haltech harness go to a junction right next to the battery, and the battery negative goes straight to the battery negative terminal. I have 4AWG ground cables running from the battery to the middle iron on the block, then another from the same spot back to the firewall. Other sensors seem to be working fine but this is also the only functional SPI I have planned right now

 

Is it worth trying to put the clutch on a different SPI since this one is acting funny? I’m hesitant because I don’t want to wind up damaging anything else if I did damage SPI 1 somehow, but I’m also not sure what else to try

 

I never did figure out this exact issue, but for anyone in the future who finds this post I later realized the wiring harness underneath the dash and above the pedals had corroded while sitting for 2 years in my driveway. A couple wires were shorting to the firewall. I only realized this when I tracked down a battery drain issue to a stretch of wire between the fusebox and body harness connector. I assume the clutch switch wiring is also damaged. For now I will just not use it