Why is My Vehicle Not Starting with the NOCO Boost # 329-GB40 Connected?

Updated 07/14/2025 | Published 06/17/2022

Question:

Gentlemen, Have the GB40 for quite some time. Just it once successfully. This morning when trying to help it failed. Two red lights, one yellow and the green were on, but did not start the motor. I measured 5.2 Volts at the 12 Volt out put. After fully charging, steady green light, I git not more than 6.9V. Is there something wrong?

asked by: Helmut S

Expert Reply:

Great question! I went ahead and brought this to the attention of my tech at NOCO. He confirmed that as part of the safety measures of the NOCO Boost Plus # 329-GB40, no current will be flowing to the clamps unless it is connected to that battery that is recognized or the device has had Manual Override enabled.

When you power it on, the charging lights should all be solid. Then, when you place the clamps on the battery, and the battery is recognized, the charging lights will race and you can start the vehicle. If they don't race, Manual Override will be necessary. Remove the clamps from the battery. Press the ! for 3-5 seconds until the BOOST light comes on. Manual Override will not be enabled if you still have the device connected to the battery when attempting to press the ! button. Place the clamps back on the battery and now you can start the vehicle.

expert reply by: Bob C

Katel

11/10/2024

I finally got the GB20 because I have a persistent problem with my Audi etron and the 12v battery dying or draining for unknown reasons. Your reply and tip just saved me - worked like a charm and I’m so glad I don’t have to get towed or head to the Audi dealer. Thanks!!

Richard L.

7/12/2025

Thank you very much. I did what you said and it solved my problem. I own a subaru outback that I seldom use and need to frequently noco because the car's battery runs low. You saved me money!!!