Electronic/Electric question

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I have been dealing with an intermittent issue related to the handheld controller of my FiTech EFI. The handheld will go off randomly until later that it has finally gone off for good, which is a good thing because I have been able to troubleshoot it. 

The short story is that power was not getting to the handheld. I can measure 12v at the plug that comes from the EFI, but the handheld does not turn on. I know it is the handheld not turning on instead of the screen. I first thought it was the jack in the handheld, but I was able to find a universal power supply with a similar plug that is able to turn it on. So what I have now is a handheld that can I can turn on with a universal transformer/plug but not with the power plug coming from the EFI. However, the strange thing is that I am able to measure 12v on the plug coming from the EFI. So could there be something in the electronic circuit of the EFI that allows me to measure 12v at the plug, but when under load from the handheld it is losing power? It would be hard without cutting into the line to measure the voltage while the handheld is connected, but that may be an option.

At some point I thought it could be the plug on the line from the EFI so I replaced it with the same result. I actually tried the same plug fed with power from the EFI and power from the power supply to find the same issue. It doesn't work when powered by the EFI even though I can measure 12v. :classic_angry:

 

Don C

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I assume you are using a digital volt meter when you measure the 12 volts at the controller end of the cable, and also at the EFI. Do you have access to an analog voltmeter? An analog voltmeter has a lot lower resistance, which will load the circuit, similar to the resistance wire running to your coil, and reduce the voltage on a "loaded"  circuit.

I suspect your controller cable has a bad connection or a bad wire, which will supply enough voltage to be measured by a digital meter, but cannot supply 12 volts under load, similar to a corroded connection on a battery cable, which will measure 12 volts but not be able to supply enough current to power lights or starter.

 
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I assume you are using a digital volt meter when you measure the 12 volts at the controller end of the cable, and also at the EFI. Do you have access to an analog voltmeter? An analog voltmeter has a lot lower resistance, which will load the circuit, similar to the resistance wire running to your coil, and reduce the voltage on a "loaded"  circuit.

I suspect your controller cable has a bad connection or a bad wire, which will supply enough voltage to be measured by a digital meter, but cannot supply 12 volts under load, similar to a corroded connection on a battery cable, which will measure 12 volts but not be able to supply enough current to power lights or starter.
I think you are onto something but the handheld should be using very little current. I could try loading the circuit with a LED or something that allows me to measure the voltage under load - I don't have access to an analog voltmeter. Also, maybe I can measure the amps when running the handheld through the universal power supply.

 
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To recap! I ended up connecting the cable directly to the battery through a fuse and it is working well.  There is definitely an issue with the power coming from the EFI CPU that although I can measure voltage it can't turn on the handheld. The power from the CPU is always on so connected directly to the battery should be the same. It just adds one more wire to the engine bay.

 

TheDude

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Hmm, that's odd. I had the same kind of problem but it ended up being the cable from the EFI to the controller. I happened to have an extra cable so that it was straight forward to figure out fortunately. Odd thing was my cable went bad after I did some cleaning under the hood. Thought it was just some water got in somewhere so I blew things out and left it disconnected for a long time with engine heat to try and try things out but it never started working right again. No idea how that could have damaged the cable but apparently it did. 

 
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Hmm, that's odd. I had the same kind of problem but it ended up being the cable from the EFI to the controller. I happened to have an extra cable so that it was straight forward to figure out fortunately. Odd thing was my cable went bad after I did some cleaning under the hood. Thought it was just some water got in somewhere so I blew things out and left it disconnected for a long time with engine heat to try and try things out but it never started working right again. No idea how that could have damaged the cable but apparently it did. 
Interesting to know. In my case I am still using FiTech's power cable to the controller but instead of it being connected to the EFI I connected it straight to the battery. It just happens that the end connector on the engine side is pretty universal and I had a few of those laying around. Maybe the cable is junk but after connecting it straight to the battery it has more juice to power the controller. Based on what happened to you, I will check the resistance of the power cable just in case. I didn't think about that!

 
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As a follow up. I checked the resistance of the cable and it is near zero so in my case it is not the cable. I think it is either the CPU or the wire/connection from the CPU. I probably won't troubleshoot it anymore since I have it working connected to BATT.

 

TheDude

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Cool, yeah it did sound different than mine for sure. Just wanted to share in case that was helpful. 

 
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