I should say the contact of the wire, where the relay would plug in, it reads those values.

At the fan wires that plug in, I get about 9v in Lo, 2 ,3, shouldn't the fan be kicking on if those are the readings?
So I think we know the blower switch into the resistor is working fine, fuses are good. But coming out of the resistor the voltage does not vary as expected. the relay probably does it's job, but why sometimes do I have Hi speed and sometimes not?

From the relay to the fan, it's reading 0 v in Off and Hi (currently it isn't running in Hi). The fan runs with 12V directly from battery, but it is reading 9V in Lo, 2, 3 speeds, the fan should work with 9V right? the voltage varies the speeds?

Could we rule out the heater core or restricted airflow?



Still waiting on the resistor wiring harness in mail, have put in a new resistor, I tried a new fan but took that back. Still have a new relay, same results, could it be a short somewhere in the wiring?

Thanks for all the help and suggestions! Need some heat or it won't get much use this winter!

 

Now that I think about it, this is expected since it's open circuit. Only with the fan running you would see lower voltages here.



The heater core has zero influence on whether the motor turns on or not. It only affects air temperature.
If the fan were running, but restricted you would hear that wouldn't you?

not necessarily. It's a voltage with no load.
Try connecting a test light across the dark blue wire and ground, as a substitute.

Bad connection somewhere, broken wire, etc.
Try applying 12v directly to the orange wire. That should energize the relay and give you high speed

a short from power to ground should blow the fuse.