I have heard stories of engines overheating extremely high without the driver even noticing, even with an aftermarket water gauge.

- i have a defi d-gauge for my water temp that works great..but im afraid one day ill be talking to a friend or watching the road when my temps suddenly shoot up to 260F from a broken hose, etc

any ideas on how to rig up / purchase some kind of beeping alarm system that i can run in sync with this gauge...i know the digital defi gauges with controllers include alarms but id rather try to fab up something myself

 

All you need is a sender with a warning contact. If you can locate a Defi compatible sender with warning contact you'd just replace your current one with the new one that incorporates the switch. If you can't find a Defi compatible sender with a warning contact you'd need to install the warning contact sender in addition to the Defi one currently running the gauge.

The warning contact is a switch inside the sender that closes at a certain temp. You can use this to turn on an indicator or an alarm for instance (or run something like a fan relay).

Most racecar supply places who sell gauges have such things. Egauges carries some as well:

http://www.egauges.com/vdo_send.asp?Sender=250F_120C