Slow AC fan motor
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Registered User
Joined: May 2015
Posts: 50
Slow AC fan motor
So it's a 1984 hurst olds with AC, the fan motor blows like it's supposed to, it's just not pushing as much air as I would like, are there any after market motors that will push more air?
Registered User
Joined: Feb 2010
Posts: 1,587
From: West Michigan
A few thoughts:
A brand new motor is available at any GM parts counter and is dirt simple to install.
The lower three speeds of the motor is selected by the switch on the dash and throttled by a resistor network mounted on the blower's housing under the hood. A bad resistor or bad connection could be slowing down the motor. The high speed is controlled by a relay which applies direct battery voltage. Again, a bad relay or connection could be limiting the current and this the speed.
The doors in the ductwork under the dash are particularly complicated in the '80s G-bodies and prone to failure. Verify that each setting is directing air exactly where it's supposed to and nowhere else:
1/ HEAT sends 90% to center vent under dash, 10% to defrost vents. zero to all the other dash vents.
2/ DEF sends 90% to defrost vent and 10% to center vent under dash, zero to all the other dash vents.
3/ VENT sends all air to four main sideways dash vents, zero everywhere else.
4/ NORM A/C sends air the same as Vent setting.
5/ BI-LEVEL A/C sends air the same as Norm A/C but also sends it to the lower sideways dash vents.
6/ MAX A/C is the same as Norm A/C but also sucks air from the right kick panel instead of from outside. All other settings suck the air from outside.
A brand new motor is available at any GM parts counter and is dirt simple to install.
The lower three speeds of the motor is selected by the switch on the dash and throttled by a resistor network mounted on the blower's housing under the hood. A bad resistor or bad connection could be slowing down the motor. The high speed is controlled by a relay which applies direct battery voltage. Again, a bad relay or connection could be limiting the current and this the speed.
The doors in the ductwork under the dash are particularly complicated in the '80s G-bodies and prone to failure. Verify that each setting is directing air exactly where it's supposed to and nowhere else:
1/ HEAT sends 90% to center vent under dash, 10% to defrost vents. zero to all the other dash vents.
2/ DEF sends 90% to defrost vent and 10% to center vent under dash, zero to all the other dash vents.
3/ VENT sends all air to four main sideways dash vents, zero everywhere else.
4/ NORM A/C sends air the same as Vent setting.
5/ BI-LEVEL A/C sends air the same as Norm A/C but also sends it to the lower sideways dash vents.
6/ MAX A/C is the same as Norm A/C but also sucks air from the right kick panel instead of from outside. All other settings suck the air from outside.
Registered User
Joined: Feb 2008
Posts: 11,798
From: Plano, TX
Some experience with the fan in two 86 Cutlii...
When working properly, they blew lots of air.
I have seen some issues you should check into -
Motor and blower come out in 5 minutes. Attach it directly to the battery and see how it works. Hold it tight, as it will want to twist out of your hand on startup.
If it does not blow hard and spin fast, replace motor.
While it is out, look inside at evap core and clean any dirt or leaves out. If oily, it may leak.
The flaps in the heater box have some issues. After one of my cars spit a bunch of rotten sticky foam out the heater ducts over the period of a few years, I now always get 50/50 air to dash and heater ducts. I have not looked into fixing it yet. Vacuum motors are all good. The foam I bet were internal seals.
I replaced the vacuum valve in the control panel this summer, as it leaked and tried to keep all air flow in the heater and defrost positions. 'Jiggling the handle' used to help but after a couple years, did not help.
The main AC control panel electrical connector (single brown wire) arced and burned in my mom's car, so fan speeds were lower and even intermittent after it got worse.
Check all other electrical connectors for arcing, pitting, or burning. The plastic will often be melted, so they will be evident.
When working properly, they blew lots of air.
I have seen some issues you should check into -
Motor and blower come out in 5 minutes. Attach it directly to the battery and see how it works. Hold it tight, as it will want to twist out of your hand on startup.
If it does not blow hard and spin fast, replace motor.
While it is out, look inside at evap core and clean any dirt or leaves out. If oily, it may leak.
The flaps in the heater box have some issues. After one of my cars spit a bunch of rotten sticky foam out the heater ducts over the period of a few years, I now always get 50/50 air to dash and heater ducts. I have not looked into fixing it yet. Vacuum motors are all good. The foam I bet were internal seals.
I replaced the vacuum valve in the control panel this summer, as it leaked and tried to keep all air flow in the heater and defrost positions. 'Jiggling the handle' used to help but after a couple years, did not help.
The main AC control panel electrical connector (single brown wire) arced and burned in my mom's car, so fan speeds were lower and even intermittent after it got worse.
Check all other electrical connectors for arcing, pitting, or burning. The plastic will often be melted, so they will be evident.
Thread Starter
Registered User
Joined: May 2015
Posts: 50
A few thoughts:
A brand new motor is available at any GM parts counter and is dirt simple to install.
The lower three speeds of the motor is selected by the switch on the dash and throttled by a resistor network mounted on the blower's housing under the hood. A bad resistor or bad connection could be slowing down the motor. The high speed is controlled by a relay which applies direct battery voltage. Again, a bad relay or connection could be limiting the current and this the speed.
The doors in the ductwork under the dash are particularly complicated in the '80s G-bodies and prone to failure. Verify that each setting is directing air exactly where it's supposed to and nowhere else:
1/ HEAT sends 90% to center vent under dash, 10% to defrost vents. zero to all the other dash vents.
2/ DEF sends 90% to defrost vent and 10% to center vent under dash, zero to all the other dash vents.
3/ VENT sends all air to four main sideways dash vents, zero everywhere else.
4/ NORM A/C sends air the same as Vent setting.
5/ BI-LEVEL A/C sends air the same as Norm A/C but also sends it to the lower sideways dash vents.
6/ MAX A/C is the same as Norm A/C but also sucks air from the right kick panel instead of from outside. All other settings suck the air from outside.
A brand new motor is available at any GM parts counter and is dirt simple to install.
The lower three speeds of the motor is selected by the switch on the dash and throttled by a resistor network mounted on the blower's housing under the hood. A bad resistor or bad connection could be slowing down the motor. The high speed is controlled by a relay which applies direct battery voltage. Again, a bad relay or connection could be limiting the current and this the speed.
The doors in the ductwork under the dash are particularly complicated in the '80s G-bodies and prone to failure. Verify that each setting is directing air exactly where it's supposed to and nowhere else:
1/ HEAT sends 90% to center vent under dash, 10% to defrost vents. zero to all the other dash vents.
2/ DEF sends 90% to defrost vent and 10% to center vent under dash, zero to all the other dash vents.
3/ VENT sends all air to four main sideways dash vents, zero everywhere else.
4/ NORM A/C sends air the same as Vent setting.
5/ BI-LEVEL A/C sends air the same as Norm A/C but also sends it to the lower sideways dash vents.
6/ MAX A/C is the same as Norm A/C but also sucks air from the right kick panel instead of from outside. All other settings suck the air from outside.
I know the electrical is all good, I've been thinking about the duct work. I have noticed the two Siamese type vents in the passenger side do not blow hardly any air, but it'll blow out of the 3 smaller front vents, under the dash by the console and a Teeny bit from under the column.
Is there a way I can make the air stop blowing out under the dash and make it come straight out of the vents facing passengers?
I feel if I could stop the flow underneath, it would blow harder up top...
Thanks to all the replies
Registered User
Joined: Feb 2010
Posts: 1,587
From: West Michigan
Sorry, it's hard to describe these things. I guess a more accurate description would be the nut-cooler vents. 
At least on the driver's side, it's that little vent under the steering wheel. I think the long, thin vents on the passenger side are on the same circuit? As opposed to the three squarer vents that are used for NORM A/C and VENT.
If you have air coming out of the "heater" vents (in the center, way under the dash) when you have A/C or VENT selected, you might have a stuck door (or bad actuator or leaky hose feeding the actuator).
My present 1987 442 has this problem -- sort of. When the selector has been in the HEAT position and is then switched to VENT, the door is sticky and continues to send much of the air out the heater vents. Then, the next time I take my foot off the gas, the engine vacuum increases enough to suddenly make the door SNAP into the proper position with a loud WHACK. It makes me jump every time, even though I know it's coming.
At least on the driver's side, it's that little vent under the steering wheel. I think the long, thin vents on the passenger side are on the same circuit? As opposed to the three squarer vents that are used for NORM A/C and VENT. If you have air coming out of the "heater" vents (in the center, way under the dash) when you have A/C or VENT selected, you might have a stuck door (or bad actuator or leaky hose feeding the actuator).
My present 1987 442 has this problem -- sort of. When the selector has been in the HEAT position and is then switched to VENT, the door is sticky and continues to send much of the air out the heater vents. Then, the next time I take my foot off the gas, the engine vacuum increases enough to suddenly make the door SNAP into the proper position with a loud WHACK. It makes me jump every time, even though I know it's coming.
Thread Starter
Registered User
Joined: May 2015
Posts: 50
Sorry, it's hard to describe these things. I guess a more accurate description would be the nut-cooler vents. At least on the driver's side, it's that little vent under the steering wheel. I think the long, thin vents on the passenger side are on the same circuit? As opposed to the three squarer vents that are used for NORM A/C and VENT.
If you have air coming out of the "heater" vents (in the center, way under the dash) when you have A/C or VENT selected, you might have a stuck door (or bad actuator or leaky hose feeding the actuator).
My present 1987 442 has this problem -- sort of. When the selector has been in the HEAT position and is then switched to VENT, the door is sticky and continues to send much of the air out the heater vents. Then, the next time I take my foot off the gas, the engine vacuum increases enough to suddenly make the door SNAP into the proper position with a loud WHACK. It makes me jump every time, even though I know it's coming.
At least on the driver's side, it's that little vent under the steering wheel. I think the long, thin vents on the passenger side are on the same circuit? As opposed to the three squarer vents that are used for NORM A/C and VENT. If you have air coming out of the "heater" vents (in the center, way under the dash) when you have A/C or VENT selected, you might have a stuck door (or bad actuator or leaky hose feeding the actuator).
My present 1987 442 has this problem -- sort of. When the selector has been in the HEAT position and is then switched to VENT, the door is sticky and continues to send much of the air out the heater vents. Then, the next time I take my foot off the gas, the engine vacuum increases enough to suddenly make the door SNAP into the proper position with a loud WHACK. It makes me jump every time, even though I know it's coming.
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