Is there a way to test a blower motor?


#1

Feels like the blower in my 85 Olds Cutlass doesn’t blow very hard…all the settings (1 to 4) work, so I don’t know if the resistor would have anything to do with this. Last winter, the car never seemed to get warm, even after 30 minutes of driving.



The air it blows is warm, but not hot…I felt both hoses going to/from the heater core after the car warmed up, and both were very hot…so that’s why I’m thinking maybe the blower motor just isn’t putting out enough air to warm up the car.



Any thoughts?



Thanks,

Jad


#2

Considering the car’s age it’s likely that the blower motor is dragging and needs to be replaced.
You could remove the motor and turn it by hand but that is not a very good indicator unless you’ve done a lot of them. If you’re removing it you might as well replace it since they’re cheap.

An inductive ammeter could be used to measure current draw by the motor. A good motor will draw from a couple of amps to 4-5 amps depending on blower speed. Drawing 7-10 amps means the blower is going out.

This car uses a vacuum operated heater valve and it’s possible the valve could be bad. Both hoses can be hot but this is also not a true indicator since some hot coolant may pass through it, but not enough to provide adequate heat due to insufficient volume.
You could remove the valve and install a temporary splice on the hoses to verify that the valve is the problem and it’s not related to a clogged heater core, etc.

Also make sure that vacuum is being provided to the valve when the lever is in the HEAT position.


#3

Make sure the radiator is FILLED. You should be able to compare the sound of the blower motor in your car to the sound of a blower motor in another car, and decide if they sound about the same. I’m thinking the heater core is restricted. Walmart sells a coolant system drain and flush kit. Try that to “open up” the radiator core. You didn’t remove the thermostat in an attempt to get more heat? If you did, put it back after the flushing. That could help pass hotter coolant through the heater core.


#4

Thanks, I thought about getting one from a junk yard but I think I risk getting another worn out motor, so I’ll go new. My aftermarket ammeter gauge shows a jump of about 7 or so amps when I put the blower on the highest speed, so that kinda fits what you’re saying.

I’ll check my Haynes manual for the heater valve location, but do you know where those are located on this vehicle? I should note that last year the heater core was replaced, when I bought the vehicle, in case that matters.

Thanks as usual, OK.


#5

The motor sounds quieter than other vehicles I’ve owned, like it’s not spinning as fast or blowing air as “hard”. As I mentioned above, the heater core was replaced with a new unit last year. And no, the thermostat has not been removed, and the temp stays at a steady 190 degrees throughout the time the car is running, and gets to 190 fairly quickly.
I’ll keep the coolant flush idea in mind in case a new motor doesn’t help.


#6

A quick look shows that a blower motor, new, is only 16 bucks at AutoZone. Seven amps is a bit high IMHO.
The heater valve should be on the passenger side of the engine compartment in the heater hose lines and should look like this.

With the engine running and the controls on HEAT, disconnect the vacuum line on the valve and make sure there is suction on the line.
Hope that helps. :slight_smile:


#7

From your description of the problem there may be a couple of things wrong. First you need to determine if there is a airflow problem. There could be low air flow due to an obstruction in the venting. Mice like to built homes there. The vent doors may not be working correctly also.

The temperature of the air can be affected by an air bubble in the heater core or the thermostat for the heater.

You may have trouble in both of these areas.


#8

Thanks, should I bother getting a new wheel while I’m at it? It looks like the motor comes without the wheel for that price and a wheel is $11.

I will check that heater valve and post back!


#9

does the velocity of the air increase with each turn of the blower knob? it could be a faulty fan speed control resistor.

when you turn on the AC does it NOT get as cold as it used to?

if the AC is also not up to its usual performance, then i would suspect the mentioned ‘heater valve’

the heater valve is supposed to totally shut off the hot water when you use the AC. one of the problems with them is that they malfunction, and either get stuck partly open/closed, or they open/shut spasmodically, when they feel like it.

i could cure mine, temporarily buy stopping the car, shutting the engine off for about 1 minute, and then restarting the engine, with the heat on full. that would work, until i touched the temp adjustment, and then i had to either deal with the temp, or stop again. by the way, i only did this for about a week, until i took it into the shop, and got the valve replaced.


#10

If both hoses are hot, then it’s not likely to be a diverter valve or the core. Even if the blower motor is barely moving, the air that is coming out should be roasting hot, just not large volumes of it. If you put your hand directly in front of the heater outlet, is the air hot? If not, sounds like the blend door is stuck to me.


#11

Yes, it does increase at each setting. But I did notice this summer that my A/C no longer works…had thought it was a leak in the A/C system…starting to suspect the heater valve…


#12

Unless the blower wheel is cracked, or cracked during removal, you can reuse it. To remove the wheel, loosen the nut 3 or 4 turns and then tap it a few times with a mallet. It should pop loose without destroying it.

It’s not likely the heater valve has anything to do with the A/C cooling.
After the A/C has been running for about 10 minutes note if the low pressure fitting at the firewall is sweating. It should also be cold to the touch. If it’s warm or only cool then you have a refrigerant charge problem assuming the compressor is engaged.

It’s also possible there could be a blend door problem but I would make sure that vacuum is being applied to the heater valve first before ripping into the dash.


#13

It is warm, but I wouldn’t call it roasting hot or even just hot…just warm. Where should the air be blowing from when on the “heater” setting as opposed to “vent”?


#14

The diverter door controls where the air exits. The blend door controls the mixture of outside and heater air.


#15

When I have the HVAC control setting on “Heater”, I don’t feel any air coming from the vents on the dash. When I switch to Vent, it does come through the dash vents, but only warm air like I said, and not an especially strong flow. I thought the Heater setting only sent air to the floor, is this true?


#16

After all these years the heater core could be covered with debris…


#17

Heater core was changed last year…