mortman

How do you test the heater motor? My dilemma, in finishing up my rewire of the car this is the last step, I have no idea if the blower ever worked. I have replaced the resistor in the heater box, triple checked the wiring diagram new switch at the controls and still the blower will not spin up. Using a test light I am getting juice, the strange part is when I hit the body of the switch panel the test light also lights up? In the “Off” position no juice so the switch is working. I really hate to take the heater out again if I can avoid it. How can I test the motor to isolate the problem? BTW, car did not come with AC.

Thanks

MBDiagMan

Just use jumper wires to put power to the motor and see if it spins. Put a voltmeter or test light to the power wires that lead to the motor to see if there is voltage. If there is voltage there and it's connected but not running, then the motor is bad.

mortman

I have power going to and from the motor still will not spin up. what about the voltage coming off the body of the switch? how can i isolate that problem? when i say the body i mean the whole switch assy

kalli

i'm a bit lost with what you mean.
usually there's two wires with disconnect at firewall for the heater motor (blower).
disconnect them and feed them with plus and minus directly (jumperwires etc). if that thing doesn't spin the problem is the motor or something inside it. maybe just stuck with leafs or so. but i wouldn't spend a milisecond to check on the switchboard if that doesn't work

tcrote5516

Just an FYI there is NO VOLTAGE coming off the switch and resistor pack. This is the negative side of the power situation. Positive 12v is constant to the blower and the resistor pack varies the negative feed to the motor.

mortman

TC,
could you elaborate? I am not am electrician so i don't understand, would be much appreciated.

kalli

what he means is that you can switch in two ways. either you have a switch between plus and the user (in your case the blower) but you have constant ground, te other way is you have constant plus at the user and the switch between user and ground

like this lamp (lamp: X, Switch: /)

+ ----X---/--- -
+ ----/---X--- -

when you close the switch the lamp will burn.

The horn is a very good example for a negative switched setup. The horn is always fed battery plus, and the switch (the horn button) just connects the other side of the horn to ground.

well according to tcrote5516 the blower is negative switched as well (i haven't checked, but no reason to not believe it).

that means one of the two cables going to the blower is always plus. no matter what you do with the switches. The switches then provide ground to the blower.

So all in all the original test is still valid. the first thing to check is the blower motor.
If you do have those two short cables coming out of the blower motor with disconnect. Disconnect them. Put battery+ on one cable, battery- on the other cable.
if the motor turns the motor is good and we need to check on your switches.
If the motor does not turn this way it's either blocked or not working

mortman

Kalli, thanks for the explanation, new motor coming today

mortman

NOTE to idiot self: Grounds work wonders, motor was no good though

2+2GT

You have two wires on the motor. One is 12V power, the other is ground. Test it that way, too.

From your description, we don't know if the motor is bad, or the switch, or the grounding resistor.