MkI coolant temp guage with 2 prong ABA sensor

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

Yeah, so at some point my laptop won't be riding shotgun 24/7, so I'll lose
my coolant gauge on Megatune. This is in my '79, ABA head, with MSnS.
Anyway, the stock ABA coolant temp sensor is in the coolant manifold, and
just isn't working to send info to the stock cluster guage properly. The
stock sender was a one wire, and hooking up the ABA sender with one wire to
the gauge and the other to ground just pegs the gauge. How do I know what
the expected output is from the stock sender, and how do I adjust what's
coming from this ABA one? I don't think that the stock one could be easily
adapted, as it probably grounds in the manifold, and the ABA one is
plastic, not metal. I don't have an ABA Bentley to see how it's normally
wired up. Thanks!
Cathy