Batboard

I would like to use an MSR2000 repeater as a half duplex using the antenna switch. The repeater has no cards other than the R1 audio as using an external controller. There is 14 VDC at the relay power but it does not change when in TX. Is that correct before I connect the relay?

From memory, the "high" side of the relay coil is always supplied with around 14 vdc.
The "keying" of the relay is done by grounding the "low" side of the relay coil.
That is done by Transmit / Receive circuits on the Station Control Module.
There are also circuits on that board to delay keying the exciter and PA before the T/R relay is closed.
If you don't have the SCM, you could ground that lead other ways, but the SCM has some small delay built in so that the T/R relay
contacts are kept "closed" while the PA in of the transmitter decays down to where there is no RF so the T/R relay contacts don't fry.
Are you certain that there is not a Station Control Module in there.
You really need that module for a lot of things.