Testing aux fan switch on thermostat
 

I have an 87’ 420 and I’ve decided its time to troubleshoot my A/C that’s not blowing cold so I’m checking everything on the A/C system including the aux fan. When I jumped the connectors on the A/C dryer the fan operates. But when I ground the aux fan temp switch wire from the thermostat to make sure that circuit works and the fan does not work, and I’m only getting 7.5 volts through this connection. I realize this issue is not related to my A/C not working but I want it fixed. Is there a relay on this circuit that could be bad or am I missing something else here?