You need to disconnect it from the circuit before you test it for resistance.
It is located under the dash near the blower motor.
Ifit has the c68 option (auto air) check the blower control module under the hood
RH under hood, between blower and evaporator according to diagram. The blower control module is most likely the culprit. It was on my 87 covette ,easy to replace but cost about $150.00
It is located under the hood on the passenger side, it screws into the evaporator case.
On the firewall to the right (when facing the firewall) of the blower motor.
For a car as old as a 1985 model, it could be that the heater blower motor control module has gone out. A new one for a 1985 Corvette is around $165 to $175 at auto parts stores.
I have an 89 Delta 88 and if you have Electronic Climate Control there is a control module located just right(passenger side) of center at the firewall. It is in the same location as the blower fan resister assembly on a car with standard a/c controls.
Passenger side up under the glove box. First disconnect the battery. Control module is located behind the blower motor. You may have to remove the blower to get to the module. Unplug the motor before doing so. The wires that you unplug from the blower will go straight to the control module. You will have to contort yourself to get up under there to get to it but be patient and you will get it. There are 3 7/32 screws holding it in place. The back one being the toughest to get to because there is a firewall/guard in place but it can be pushed backwards to get to the last screw. Hope this helps you out. As i am writing this I am replacing mine as well on my 97 vette.
Something called a blower control module takes the place and is found in the hole where you would find a blower resistor, so there isn't a blower resistor in that vehicle. As far as the blower control module is concerned, the module is serviced as a unit. No part can be fixed or replaced. This is not to be confused with the control head in the dash. The blower control module is held into the heater box with two 8mm screws outside the firewall under the hood, where you would normally find the blower resistor pack.
I think under the hood covered with shroud on the firewall.
Behind glove-box, behind engine control module