Heater blower

[tucknroll]

Hey 69 charger here.  My fan blows good heat but not hard enough.  Do the blower motors get weaker and maybe a new one will blow harder?  Thanks

[b5blue]

Check the resisters.

[tucknroll]

It's working on high and low so I think it's just worn out

[John_Kunkel]

Temporarily connect the motor directly to battery voltage and compare the output to HIGH on the control panel.

[tucknroll]

Good idea thanks

[Nacho-RT74]

Question...
 Is it an A/C car?

[tucknroll]

Where do I check the resistors please?

[tucknroll]

So I connected it straight to the battery and it turned super fast but I plugged it back up and it ran slow again.  Any ideas?

[b5blue]

follow connectors

[John_Kunkel]

You've proved that the motor is good so now look at the resistor block or the fan switch. It's not uncommon to find the spade connectors at the fan switch fried.

[tucknroll]

How do I bypass the resistor? Running on high is fine with me

[purple70rt]

How do I bypass the resistor? Running on high is fine with me

awesome...

[John_Kunkel]

How do I bypass the resistor? Running on high is fine with me

Not sure if that is a good idea, bypassing the resistor block permanently might overheat the motor.

Looking at the wiring diagram, it appears that there is some resistance even in the high mode...IOW, it never runs at full 12V.

[b5blue]

Jump in and out 12V with a fuse.

[Nacho-RT74]

Question again...

IS IT AN A/C CAR?

A/C cars get just one speed for heater function AND is a lower speed than the A/C low... as far I recall.

[tucknroll]

Yes it's an ac car

[John_Kunkel]

Question again...

IS IT AN A/C CAR?

A/C cars get just one speed for heater function AND is a lower speed than the A/C low... as far I recall.

Looking at the schematic, the blower motor controls are the same for A/C or not and I was wrong, HI bypasses the resistor.

[Nacho-RT74]

Yeap, High bypasses the resistor block. Is spliced into the same line coming from block resistor output (dark green) running to the blower


But for Heater function on A/C cars, they use to be a single speed (dark brown wire line) slower than the low AC speed. No speed selection for heater function. That's on my 74 at least. Hence why I'm asking to the OP about this.

Will need to check further on earliers diagram thought, but on a simple view, the Dark brown signals goes throught All The resistors line up to dark green which is the output to the blower. This is of course if the dark brown wire is hot coming from control switch while no other wire coming from control switch is hot... tipically tan wire which is the default speed for A/C and Vent functions coming from control switch (not from speed selector) and light green wire which is mid speed, coming from blower speed selector, STILL with tan wire to resistor being hot. Speed selector is sourced from same line but the Ohms law makes the mid speed line coming from speed selector a priority over the rest of hot sources.

(I hope sounds clear enough)

[Nacho-RT74]

Here is the route for the blower power for heater function.

At control switch arrives the 14Bk wire power (from Acc) which fill feed either the Heater function (14BR) or the A/C-Vent function (14T) to the speed switch, but not both at the same time.

The brown line will run through all the resistors up to the blower. So will get the more reduced voltage rate of all, so the lower speed posibility, including the A/C Low speed.

With this selection, all other power splices can be despited since will be running practically to nowhere or buckling into the same existant resistor circuit with power already reduced. Except the one for the time relay to the compressor what will be activated anyway straight from control switch (no resistor up to the TDR)



I can explain how the speeds selector setup works on this network if required.

[tucknroll]

Thanks guys

[Nacho-RT74]

A side note and making some correction: the blower speed switch could still make some small speed variation between low mid and high BUT still running throught the heater resistor section. Once the brown circuit is activated there is no way to bypass the first resistor between C4 and C7 but the C7 Tan wire will reach the speeds switch throught C7A, and when selecting mid speed a new source of power C6A (already coming from first resistor) will bypass the second resistor. When selecting high speed, power will run throught C5A to straight feed the blower, but still and once again, after run throught the first resistor between C4 and C7 circuits.

I'm pretty sure on my 74 I don't have speed selection when Heater is selected. I can't recall the diagram or its function on my car because since factory, the water pump nipples to the heater were sealed (heater is not REALLY needed in Venezuela) and when I made it to put in working order I just used the heater maybe couple of times.

[John_Kunkel]

The subject here is a '69 and the high speed. If the motor speed is higher when hooking battery voltage directly to the motor, there is resistance somewhere in the normal circuitry. I would look at all the spade connectors at the mode switch and the fan switch. These connectors are open to the atmosphere and have probably picked up some corrosion over the ensuing 55+ years.

[Nacho-RT74]

I'm saying based at least on diagram and on my revised analysis, the blower won't reach ever the same max speed like the one got on a straight feed from batt while Heater function, being the heater function for blower runs from the brown wire circuit, which is feeded no matter what throught at least ONE of the resistors (circled in red)

A/C-Vent max speed is faster, being the same that being batt feeding (or close, depending on contacts quality)

Aside that, is true the blower speed switch inside is prone to bad contacts

(Below, what's the wire/circuit will command the power on high speed)

[Nacho-RT74]

BTW... what in diagrams says LOW on the C6A-LGN wire/circuit is actually MID speed. When setting LOW speed on A/C-Vent (and also for heater, but just coming from resistor block first) the speed switch input is really going to nowhere like turned off and circuit is feeded by the TAN C6 circuit, straight from control switch to the resistor block, then leaving the resistor block on the C5B-DGN wire wich is the output for all speeds, Including high speed, but bypassing the resistor block from speeds switch (except as mentioned the Heater function which still gets power running throught the circled resistor)

I hope sounds clear