Rear 12V Harness Voltage Check

[Mike]

Hi all,

I wanted to check the 12v voltage when the vehicle was asleep so I was trying to use the rear tow hitch 12v harness with a generic auto multimeter. The multimeter doesn't seem to detect voltage and switches to ohms automatically. Anyone have any idea why this is? I thought it was due to the connections being covered with adhesive from the electrical tape that was covering them so I cleaned them with isopropyl alcohol and it didn't make any difference.

I thought it was the multimeter, so I tested it with a 1.5V D battery and it worked fine, and tested it on a new 12V in a relatives Rav4 and it worked. Is it possible for the rear 12V harness to be disconnected? If so is there a way to reconnect it to the 12V battery? I removed the frunk cover and both 12V batteries (2x, 2022) look to have all connections but I didn't remove the cover and test directly since the batteries themselves are perfectly fine (and the vehicle service menu does show normal voltage when the vehicle is awake.) I just wanted to do this to check what the voltage is easily when the vehicle is asleep out of curiosity once in a while, no actual issues with the vehicle.

Am I stupid and missing something?

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[UnsungZero_OldTimeAdMan]

Those leads in the back are for jumping only. Those with better memory can correct me, but I think there is a diode in that harness to allow current flowing only in one direction and can't be used to read voltage.

I think you can see voltage by going into the hidden RiDE service menus. Or, once you've got physical access to the 12V. For gen 1, you need to unclip the cowling between the wipers and the frunk. The 12V is under that and on the driver side.

 

[ndmiller]

What was the reading when the vehicle was not asleep? Say when preconditioning to a time set in the app? That would certainly use the 12V

 

[srkz]

Was your vehicle awake? It goes to sleep pretty quickly after you close all the doors. Open a door and try again.

 

[SwampNut]

I wanted to check the 12v voltage when the vehicle was asleep

...For what purpose? I mean, you found your answer, 0v. As others said I would expect this to be a current-limited one-way connection, not intended to carry loads. What is it you're trying to do?

 

[Mike]

Thanks guys. I didn't realize the rear harness was one-way input only. Never read it anywhere.

 

[UnsungZero_OldTimeAdMan]

Thanks guys. I didn't realize the rear harness was one-way input only. Never read it anywhere.

I'm certain is for safety reasons. Think "what could possibly go wrong" and you'll get it.

 

[technerd]

FWIW I installed a $30 bluetooth battery monitor on my Gen 1, which is still on the original batteries, to monitor. Good to be able to see the stats, which are probably not looking good haha.

 

[SwampNut]

I'm certain is for safety reasons. Think "what could possibly go wrong" and you'll get it.

An idiot tow truck driver just rolled mine up and stuffed it in, no care about the terminals touching.

 

[Dasoss]

Hi all,

I wanted to check the 12v voltage when the vehicle was asleep so I was trying to use the rear tow hitch 12v harness with a generic auto multimeter. The multimeter doesn't seem to detect voltage and switches to ohms automatically. Anyone have any idea why this is? I thought it was due to the connections being covered with adhesive from the electrical tape that was covering them so I cleaned them with isopropyl alcohol and it didn't make any difference.

I thought it was the multimeter, so I tested it with a 1.5V D battery and it worked fine, and tested it on a new 12V in a relatives Rav4 and it worked. Is it possible for the rear 12V harness to be disconnected? If so is there a way to reconnect it to the 12V battery? I removed the frunk cover and both 12V batteries (2x, 2022) look to have all connections but I didn't remove the cover and test directly since the batteries themselves are perfectly fine (and the vehicle service menu does show normal voltage when the vehicle is awake.) I just wanted to do this to check what the voltage is easily when the vehicle is asleep out of curiosity once in a while, no actual issues with the vehicle.

Am I stupid and missing something?

The clue is that your DVM automatically switched to ohms. That tells me that your meter was in the auto mode rather than the dc Volts mode. In the auto mode your meter presents a load of about 2 K Ohms at the test leads rather than 10 M ohm. There is a diode or something in the jumper circuit that only allows current flow into the battery. The meter might read something in the (higher resistance ) Volts mode but it wouldn't be the actual battery voltage--just diode leakage.

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