Review on WirthCo 20092 Battery Doctor Isolator by Joseph Whiteman

secondary battery voltage 12.5v, main battery 12.9v with engine off. With the motor on the main battery it reads 13.6 on the poles. The dealer states that this is the normal charge voltage for the Toyota Tundra. The blue light on the Battery Doctor starts blinking when I start the truck, indicating that it's charging. The auxiliary battery voltage stays at 12.5 until I press the lock button when the blue light goes out and the auxiliary voltage jumps to 13.1. After a few seconds (maybe 5) the blue light will start flashing again and the auxiliary battery voltage will drop to 12.5. The auxiliary battery has blown at 20A and the fuse has not blown. I am outside the return period. The WirthCo website does not have a technical support email address. I think this product does not work as advertised. Very disappointed, cannot recommend this product. Update: I emailed sales@wirthco.com asking for tech support. I received an email reply and the technician was very helpful, but the problem was not resolved. I was asked to pack the unit and send it back to Wirthco as a warranty return. Lets see what happens. Update (9/11/19) - I sent the device back to wirthco at my own expense. They checked the unit, found it was not working properly, and sent a replacement at their own expense. Wirthco believes the unit worked properly during shipment but failed due to the use of the wrong gauge wire between the insulator and the auxiliary battery. While I have my doubts as to the root cause, I have no other reasonable guess as to why the device failed. I bought this device in late 2018 and Wirthco will be replacing it in September 2019 so they certainly support their product. Although it was a trial period, I was very happy with the support I received from Wirthco. Improving my score from 1 to 3 based on extensive technical support. I will update again as soon as I install a replacement unit. Updated 07/17/20. I tried using the device for the first time this year and the blue light flashes again and the battery is low. This product worked for about 3 weeks last fall but is not working now. Tried different batteries with no success. The blue light keeps flashing. The installation was in the tundra in 2011. Back to connecting the 12v power to my 7 pin trailer socket. I'm sorry I bought this. Would not recommend this product.