Heater Blower Switch

[Gluchie]

On my 72 NYB something burned out the blower switch. One connector was off and the plug was melted. I purchased a new switch and plug and I am not getting power to the switch. I found a power source and by-passed the switch and the blower works. It was suggested that the blower resistor might be bad. I also purchased a NOS resistor and replaced. There is no power at the resistor either. Fuse looked good but replaced anyway. Trying to follow the schematic to locate the initial power source has been futile probably, because i have no idea what some of the symbols represent. Anyone have any ideas where to look? Appreciate any thoughts. Below is pic
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[71NewYorkMan]

Your car has heat only? Or AC & Heat?
Are the radio and back-up lamps working?

 

[Gluchie]

AC and heat. Radio is an after market there when purchased but appears to be functioning correctly. I will have to verify backup lights after work

 

[Big_John]

On my 72 NYB something burned out the blower switch. One connector was off and the plug was melted. I purchased a new switch and plug and I am not getting power to the switch. I found a power source and by-passed the switch and the blower works. It was suggested that the blower resistor might be bad. I also purchased a NOS resistor and replaced. There is no power at the resistor either. Fuse looked good but replaced anyway. Trying to follow the schematic to locate the initial power source has been futile probably, because i have no idea what some of the symbols represent. Anyone have any ideas where to look? Appreciate any thoughts. Below is pic
gView attachment 317339

What you have is too much current draw going through the switch. Most likely the blower motor is getting tired and it's getting hard to turn. It will still work, but the amount of current needed has increased. Put that with a switch that's worn out and it creates heat. Heat starts making all the connections and switch contacts bad... Creates more current draw that creates more heat etc.

Replace the blower motor and switch. Clean all the connections and you'll be fine.

Looking at the power source is going the wrong direction. Look at what the switch feeds instead.

 

[Gluchie]

Thanks. make sense. Now to find a blower

 

[furious70]

AutoZone and rock auto have them

I also put the power for mine on a relay so only the trigger current goes through the oem harness. Motor current through new wiring.

 

[Gluchie]

I will have to look into that.
Thanks all!!

 

[Gluchie]

Went to rockauto and they have single shaft and dual shaft motors. Is there a way to determine which I have without taking the old one out? I am not trying to be an idiot because I believe I already am.

 

[jct]

You want single shaft, dual shaft is for the option with the rear heater

 

[Gluchie]

Thanks.

 

[71NewYorkMan]

I purchased a new switch and plug and I am not getting power to the switch.

I also purchased a NOS resistor and replaced. There is no power at the resistor either.

Replace the blower motor and switch.

If I understand correctly, you have already replaced your switch and resistor? Blower works when connected to alternate power source? This would mean that the designed power source is still not working? I asked about the radio and back-up lamps because they feed from the same "AUX" supply in the fuse box as the AC/Heat blower. The complete power source: Battery to ignition switch to fuse box "AUX" to AC/Heat fuse to AC/Heat control switch to blower switch. Many steps in between, including a blower relay that operates in "AC" mode.
Before you replace your blower, you may want to determine how many amps it is drawing using a DC clamp ammeter. I only mention all the complexity because you suggest the blower works on an alternate source, indicating something is wrong elsewhere, despite all the parts you have already replaced.

 

[71NewYorkMan]

BTW- This is the motor you would need if you decide to change it.
More Information for VDO PM202

 

[Gluchie]

AC and heat. Radio is an after market there when purchased but appears to be functioning correctly. I will have to verify backup lights after work

Sorry for the delay. Yes, the backup lights do work. I believe, but cannot confirm that the radio is wired correctly, but yes it works as well.

 

[71NewYorkMan]

You have now proven the power path through the key switch to the fuse box. Since you already replaced the heater fuse, the next step is to check the power through the main harness heater connector ( 1 ) on the attached drawing. After that the connector on the back of the push button vacuum switch (2) passes power directly to the blower switch (3- AC mode), or through an extra resistor (3-heat mode)in the blower resistor block you changed.

Connector (1) is a male-female quick connect with 12# Black wire w/tracer. The connector should be close behind the control in the dash.