Linking HFL (Blue Tooth) power to a separate relay to prevent drain. - Acura MDX Forum : Acura MDX SUV Forums
 
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post #1 of 8 (permalink) Old 12-13-2018 Thread Starter
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Linking HFL (Blue Tooth) power to a separate relay to prevent drain.

I have the same issue that lots of folks here do with the HFL module occasionally staying active and draining the battery. The dealership replaced it once under warranty so I'm not going to do it again on my dime. I currently have it unplugged but I'm wondering why I couldn't just route its power line through a relay triggered by an ignition controlled source.

If the main power line in the factory HFL harness was cut and routed through a 12v relay, that was triggered by anything I can find that is only hot when the ignition is turned on, then that would disable the unit when the car was powered off and re-enable it when the key was turned on.

This seems like a relatively simple, albeit annoying, fix but I'm not sure if I am missing something about the units wiring or the way the brains of the car interact with it.

Thoughts?

TIA

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post #2 of 8 (permalink) Old 12-13-2018
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There is a post with the fix as you had suggested. There is even a video on how to do it right. I never bothered with fixing mine.

Good luck!

PS. I have attached a wiring schema that I found at the time of my researching the topic. Hope it helps. You may be able to locate the video on youtube.
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File Type: pdf BlueToothPwr.pdf (7.9 KB, 33 views)
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post #3 of 8 (permalink) Old 12-13-2018
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I came up with the relay idea as it is used in other electronic sub-systems in cars. I have been using the relay for over three or four years now. I really can't remember exactly. In summary, there are no adverse effects in the module communicating with the other systems (radio, navigation screen, steering wheel commands, etc.) with this mod. No side effects in its memory or configuration either. Only side effect is the module is totally with NO power.


I created a PDF with all of the information for the mod, I also included a Radio Shack part number for the relay. I went with a simple solution because of time. However, I was looking to replicate the design of the module which should stay ON up to 15 minutes after the ignition has been set to OFF. This can be made with a diode, a resistor and a capacitor as a simple timer operating on a low voltage (1.5VDC) relay instead of a 12 VDC relay. Anyways, I asked myself, How many people (including me) stay talking on the car's BT with the vehicle totally OFF? That is why I opted for simple: ignition OFF = BT OFF. Ignition ON or ACC = BT ON.

datmdx just found and attached the initial file I posted. I will post the latest file with more information.


Did I addressed your concerns at this time?
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post #4 of 8 (permalink) Old 12-13-2018
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This is how mine looks like
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post #5 of 8 (permalink) Old 12-14-2018 Thread Starter
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Thanks, it seemed like it made sense so I'm glad to know it does.

The attached wiring diagram above is just a basic layout for the relay.
- What color wire from the harness is the primary power (+) for the HFL?
- What did you use for a signal wire and where is it?

Thanks
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post #6 of 8 (permalink) Old 12-14-2018
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11MDX,


Here is the file you need. You will be required to do tin soldering at the relay and cables. I used heat shrink tubing for electrical insulation.
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File Type: pdf BlueToothPwr_v1.1.pdf (23.1 KB, 41 views)
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post #7 of 8 (permalink) Old 4 Weeks Ago
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Quote:
Originally Posted by PRGonzalez View Post
I came up with the relay idea as it is used in other electronic sub-systems in cars. I have been using the relay for over three or four years now. I really can't remember exactly. In summary, there are no adverse effects in the module communicating with the other systems (radio, navigation screen, steering wheel commands, etc.) with this mod. No side effects in its memory or configuration either. Only side effect is the module is totally with NO power.


I created a PDF with all of the information for the mod, I also included a Radio Shack part number for the relay. I went with a simple solution because of time. However, I was looking to replicate the design of the module which should stay ON up to 15 minutes after the ignition has been set to OFF. This can be made with a diode, a resistor and a capacitor as a simple timer operating on a low voltage (1.5VDC) relay instead of a 12 VDC relay. Anyways, I asked myself, How many people (including me) stay talking on the car's BT with the vehicle totally OFF? That is why I opted for simple: ignition OFF = BT OFF. Ignition ON or ACC = BT ON.

datmdx just found and attached the initial file I posted. I will post the latest file with more information.


Did I addressed your concerns at this time?
Why not just cut the battery line and connect the ACC to the battery line of HFL. Same thing without relay needed.
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post #8 of 8 (permalink) Old 4 Weeks Ago
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Quote:
Originally Posted by domike View Post
Why not just cut the battery line and connect the ACC to the battery line of HFL. Same thing without relay needed.

Good question. The relay idea popped first into my mind. Plus, I have no +B wires hanging in there with no connection.

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