Pro Pressure TPMS Sending Units

[tmmar]

I have the Pro Pressure TPMS and it is about 3 years old. I have read that the sending units will last about 3 years and I was wondering if the was a way for me to replace the batteries in the units or if some one knows about a place that will replace the batteries. I think that new sending units cost about $50 each so $300 for 6 new sending units is quite pricey.
Thanks.

[MtnGuy]

I have had my Pressure Pro sensors since July 2007, and the batteries are still good. I did have 1 sensor that went bad, and Pressure Pro sold me another at a discount. It was my understanding when I bought my system, that the batteries were not owner replaceable. It was also my understanding that a battery replacement would cost $35 instead of the $50 for another unit.