RunnerGirl77 says:Ricardomt, if it is definately the strap that is heating up (as opposed to bodily heat from contact), this is an issue worth taking up with Garmin. First, check with the place you purchased it from; perhaps, given that you just bought it, they will exchange the strap, saving you some work.
If not, Garmin (at least here in the states) has been super quick with repair service every time I've dealt with them. Over the course of the last five years, I've seen four units, all eTrex units for hiking, sent in for service (the issues were caused by human misuse, like dropping or switching the flow on batteries, not a fault of the unit, although the unit was compromised by the action)(Did I mention that I teach gps clinics to new users?).
First, you have to contact Garmin for an RMA number. Either email them through
www.garmin.com, or phone them at 1-800-800-1020. Then you ship the unit to a specified address for repair.
Garmin International
1200 E. 151st Street
RMA Number: (insert your RMA number here)
Dock Door #18
Olathe, KS 66062 USA
That repair center might be somewhere other than the states for you, so you'll want to ask. They usually have the unit back in my hands within a week; it might be a bit longer, given your location.
One last thing, I mentioned batteries being put back in incorrectly, causing the power to overload the unit. It is worth checking to make sure that the factory workers put the battery into the strap correctly. Take a thick coin (I use a US nickel), and use it to turn the circular battery cover counter-clockwise in the strap. Be sure to put the HRM strap on a firm surface when doing this, and press down a bit. The battery should be connector side down, with the type and brand of battery showing on top as you look at it. I would think that it wouldn't work the other way, but who knows. A friend of mine put batteries backwards into an Garmin eTrex and fried it's little software brain, so anything is possible. Good luck with this. Follow up on the issue now, while the purchase receipt is still fresh.