0

I replaced the battery in my key fob transmitter 1 year ago. The voltage seems fine on key fobs (2.92v). Edit: I ordered new batteries in case those batteries are lower under actual load, or it needs 3v+.

I want to narrow the problem to either the key fob or the car. I've been told that most cars have a special dedicated battery for the receiver (in the car). But my owners manual makes no mention of that.

The answer for the 2005 Mazda-3 may work.

Edit:

Remote got weaker last year. Replaced battery. It got weaker again. But voltage seems fine. (And last battery was used and lasted 4 years).

A mechanic told me that, in general, the anti theft systems often have a separate battery (to prevent thieves from from disconnecting the battery). And the keyless entry uses that system. My owner's manual mentions A system to prevent the car from being started with the proper key. It does not mention a separate battery.

Test results I tested the voltage of both remotes after use: 2.92v and 2.95 via multimeter with no load (I don't have a resistor ). (Labelled as 3v batteries)

Main battery 12.1v with lights on, measured from outer edge of connector on battery.

Clay Nichols
  • 175
  • 5

1 Answers1

2

The 2010 Mazda 3 has only a single battery for the entire vehicle, and it's the big one in the engine compartment.

To the best of my knowledge, no vehicle on the road today has a separate battery for the remote receiver. A car/truck remote receiver has to be "on" all the time to "listen" for the remote transmitter's signal. This constant-on condition would drain a small hidden battery in short order.

Suggest you check your owner's manual and verify that the key fob's battery is installed in the right direction. If you are equipped with a digital voltmeter and the key fob uses a lithium coin cell, verify that the cell's voltage is more than 3V both before and after transmitting. A nearly-dead lithium coin cell can recover to 3V between uses but drop to a low voltage when you use it. Coin cells purchased online are often dead or nearly dead on arrival.

Results as reported by OP

"New coin battery for remote measured 3.2v with multimeter. Put new batteries in remotes and both work."

MTA
  • 10,754
  • 1
  • 12
  • 38