Heater Diagnosis and Testing

Bramick_old · December 3, 2008 at 7:12 AM

I'm looking at my 65 Shop Manual 16-4..

My blower isn't coming on at all using the heater controls. Looks like it's one of the following issues:

1. Burned out fuse or loose wires.

2. Defective motor ground, or defective blower motor.

4. Defective motor switch.

Originally the heater worked, but given I don't drive it a lot in colder weather. So a some point it stopped working. I'm thinking it's probably a fuse/loose wire or motor switch.

Any suggestions on what it probably is?

Looks like I'll be buying a wiring manual too. Probably this one: http://www.virginiaclassicmustang.com/catalog/shop/item.asp?itemid=LT265

zray · December 3, 2008 at 8:51 AM

try direct current to the motor. If it works, then you have a switch or wiring issue.

good luck.

Z. Ray

RalphJr · December 3, 2008 at 2:55 PM

If you have the later 3 speed set up (switch OFF all the way to the left) I have a good used switch and wiring.

You also need to check your resistor assembly in the front of the heater box - red plate right in the middle of the front - this controls the various speed settings. When this breaks the blower motor won't get power - Scott Drake repops this part I think.

4 out of 5 of my Mustangs have all had the later 3 speed system - not sure how the eariler 2 speed system works - my 64 1/2 car never had problems.

A wiring diagram will definitely help - good investment.

Bramick_old · December 3, 2008 at 10:47 PM

Thanks guys. I test the blower and go from there.

I'm pretty sure mine is a 2 speed system. Middle is off. Left is low. Right is high.

SixfiveGT · December 4, 2008 at 12:06 PM

Bramick:

I have run into this problem several times in the past and each time it turned out to be the resistor pack located on the heater box. that's the red block with the three terminals that is connected to the heater switch on the dash located under the glove box. First try taking the connector off the resistor and clean the contacts replace the plug and make sure the connections are tight if the heater motor still doesn't work do an ohm meter check to see if you have an open resistor. If the resistor is bad it is a simple replacement. Hope this helps

C6ZZKGT · December 4, 2008 at 12:17 PM Official Post

The two speed system does not use the resistor block like the three speed system does.

-Fred-

Bramick_old · December 31, 2008 at 9:43 AM

I just replaced a heater control wire that broke off at the end. Man those are some boogers to get to. I thought I'd never get the z end that connects to the switch in place!

Participate now!