Beep Beep Beep

Have I found the source of the annoying noise?

If you dredge back 18 months in this blog you’ll probably find where I wrote about fitting a Tyre Pressure monitoring system (TPMS) to the Isuzu 4WD.  TPMS has been mandatory for new vehicles in the USA since 2007 and this was subsequently adopted by the EU.  Australia has yet to follow, which means most vehicles are sold without a TPMS.  Having a TPMS is an important safety feature.  A significant portion of non vehicle to vehicle incidents are caused by tyre failure and a tyre monitoring system assists in reducing that risk.

Our after market TPMS came from a Chinese eBay seller.  It consists of a control box, monitoring button, tyre sensors and antenna.  The control box has to be wired into the screen of the vehicle head unit which then displays the status of each tyre.  The screen can be displayed by either pushing the monitoring button or automatically should the status of one or more tyres go outside the user settings.  Each tyre sensor wirelessly communicates the current tyre pressure and internal temperature to the control box.

My problem is the system has never worked.  When turned on the control box emits a constant  “beep.. beep..beep” noise.  My initial assumption was I’d incorrectly wired the control box into the vehicle.  After several attempts to check the wiring I came to the conclusion there was nothing wrong with my wiring and with other projects requiring attention I suspended work on the problem. 

Several months ago I wrote to the manufacturer asking for advice on what the sound from the control box meant.  Had the control box failed or was it my wiring?  To date no answer has been received.   

A bad back and high temperatures here in Perth had me once again looking at the TPMS.  I started to think “dead battery”.  Perhaps the beeping was a warning there was a flat battery. Remember the unit is 18 months old and battery life was quoted as 5 years.   It wasn’t that difficult to work out how to dismantle the monitoring button and put a multimeter on the lithium battery.  It was fine.  This left the four sensors which are screwed onto the tyre valve stem.  They obviously contain a battery but the units looked to be sealed.  Eventually I worked out I could dismantle the sensors by placing them upside down in a vice and carefully unscrew the base with a pair of water pump pliers.  All four batteries were flat!  Is this the cause of the noise problem and defective system?  We will have to wait until the temperature falls before venturing out to purchase replacement batteries.