Help! Problem with heater blower fan

[mark1952]

I have a 1986 Corvette convertible pace car. My fan on my heater/AC does not work. I've replaced the blower switch, checked the resistor for broken wires, which it all looked in great shape, and i disconnected the blower fan and used jumper wires and hooked it up directly to the battery and it worked. After I hooked everything back up the blower motor still doesn't work. Any idea???

 

[ecss]

Verify the AC 25 amp fuse located in the passenger side end of dash is good.

The Blower motor Relay is bolted to the firewall where the two heater hoses enter the car's interior.
Turn the ignition On.
When the blower speed is set to High you should measure 12 volts on the Orange wire at the Blower motor Relay socket. You should also measure 12 volts on the Red wire at the socket. The relay should energize and you should measure 12 volts on the Purple wire which provides the power to the Blower Motor.

 

[mark1952]

Problem with heater blower motor

Verify the AC 25 amp fuse located in the passenger side end of dash is good.

The Blower motor Relay is bolted to the firewall where the two heater hoses enter the car's interior.
Turn the ignition On.
When the blower speed is set to High you should measure 12 volts on the Orange wire at the Blower motor Relay socket. You should also measure 12 volts on the Red wire at the socket. The relay should energize and you should measure 12 volts on the Purple wire which provides the power to the Blower Motor.



Good morning ecss!

I checked the fuse and it appeared to be ok. I did what you suggested and I have voltage going to the wires. So i ordered the resistor and it will be here tomorrow morning. I will let you know what happens once I have installed it. I hope that solves the problem.
Thank you for your help.

 

[Antz81]

I checked the fuse and it appeared to be ok. I did what you suggested and I have voltage going to the wires. So i ordered the resistor and it will be here tomorrow morning. I will let you know what happens once I have installed it. I hope that solves the problem.
Thank you for your help.

The test he got you to do was if it was getting 12v for high speed, if you have voltage then it's not the resistors (these only affect the lower speeds anyway)
my guess now is that you have a bad ground

 

[mark1952]

Problem with heater blower motor

The test he got you to do was if it was getting 12v for high speed, if you have voltage then it's not the resistors (these only affect the lower speeds anyway)
my guess now is that you have a bad ground

so where can i find the ground for the blower motor? i traced the wire from the fan and it's on the frame. it appears to be ok. it's never been loosened. do you still think it may be that ground??

 

[Antz81]

so where can i find the ground for the blower motor? i traced the wire from the fan and it's on the frame. it appears to be ok. it's never been loosened. do you still think it may be that ground??

If that's where you traced it to then that's probably the one. It may look good, but I'd loosen it off and give it a clean up just to be sure.

 

[ecss]

Sorry I posted the schematic for a 89 instead of a 86. I edited my first post to correct that.

The difference is the color of the wires at the relay socket.

Pin A is a Red wire and is 12 volts is a fusible link and hot all the time.
Pin B is a Dark Blue wire and comes from the resistor network has a varying voltage depending on the speed selected.
Pin C Black wire is ground for the Relay coil.
Pin D Brown wire and is 12 volts when High speed is selected. (Orange at the switch and changes to Brown at the relay socket.
Pin E is a Black/Red wire and powers the Blower Motor.


As Antz81 mentioned the test I asked you to do applies 12 volts from the Red fusible link to the blower motor.
The resistor network is bypassed.

If you had 12 volts on the Orange wire which changes to a Brown wire at the relay socket,
12 volts on the Red wire from the fusible link and 12 volts on the Black/Red wire which goes to the motor, the motor should run unless as mentioned the ground wire which goes to the frame rail is bad.

If you have an ohm meter.
Disconnect the negative battery terminal.
Measure the resistance from the negative battery terminal cable to the Black wire of the 2 pin Blower motor connector. Should read zero ohms. Anything above a couple of ohms indicates a bad connection at the frame rail.

If that checks out, reconnect the negative battery cable.
Remove the relay from it's socket. Take a paper clip or piece of wire and at the relay socket, jump the Red wire to the Black/Red wire. That provides 12 volts direct to the motor.

If that works, the relay is probably bad. You can use a screwdriver and carefully
pry the cover off the relay and inspect the relay coil and contacts.

 

[mark1952]

Problem with heater blower motor

Sorry I posted the schematic for a 89 instead of a 86. I edited my first post to correct that.

The difference is the color of the wires at the relay socket.

Pin A is a Red wire and is 12 volts is a fusible link and hot all the time.
Pin B is a Dark Blue wire and comes from the resistor network has a varying voltage depending on the speed selected.
Pin C Black wire is ground for the Relay coil.
Pin D Brown wire and is 12 volts when High speed is selected. (Orange at the switch and changes to Brown at the relay socket.
Pin E is a Black/Red wire and powers the Blower Motor.


As Antz81 mentioned the test I asked you to do applies 12 volts from the Red fusible link to the blower motor.
The resistor network is bypassed.

If you had 12 volts on the Orange wire which changes to a Brown wire at the relay socket,
12 volts on the Red wire from the fusible link and 12 volts on the Black/Red wire which goes to the motor, the motor should run unless as mentioned the ground wire which goes to the frame rail is bad.

If you have an ohm meter.
Disconnect the negative battery terminal.
Measure the resistance from the negative battery terminal cable to the Black wire of the 2 pin Blower motor connector. Should read zero ohms. Anything above a couple of ohms indicates a bad connection at the frame rail.

If that checks out, reconnect the negative battery cable.
Remove the relay from it's socket. Take a paper clip or piece of wire and at the relay socket, jump the Red wire to the Black/Red wire. That provides 12 volts direct to the motor.

If that works, the relay is probably bad. You can use a screwdriver and carefully
pry the cover off the relay and inspect the relay coil and contacts.


Ok...this is what i did. i bypassed the resistor and took a jumper and went from the red wire that is always hot and took the positive lead off the blower motor and hooked it up and the fan worked. so i'm guessing that the resistor is bad. correct??

 

[ecss]

I'll try to explain how the circuit works.

In all blower speeds except High the voltage to power the blower motor goes thru at least one resistor.
The voltage/current flow from the Dark Blue wire passes thru the normally closed contacts of the Blower motor relay then to the Black/Red wire.

In High speed mode 12 volts from the AC fuse passes thru the Blower motor relay primary coil. The relay energizes and 12 volts from the Red fusible link passes thru the normally open relay contacts and then to the Black/Red wire. **************(The resistor network is not used in this mode). ************

If you manually jumped 12 volts from the Red wire to the Blower motor and it runs that proves the blower motor is good and the 12 volts from the fusible link is good.

It does not eliminate the resistor network or the Blower motor relay.

REMOVE/UNPLUG THE BLOWER MOTOR RELAY FROM THE SOCKET.

Turn the ignition On.
Set the C60 manual HVAC rotary dial to anything except Off.
Set blower speed to Hi
Set the volt meter to read DC
Red probe on the Brown wire at the relay socket
Black probe to Black wire.
Should measure 12 volts.
If no 12 volts verify the AC fuse is good.
If the fuse is good verify the Black wire at the Blower motor relay socket has zero resistance to the negative battery terminal.

If it does you should have 12 volts on the Black/Red wire going to the blower motor.

If no 12 volts on the Black/Red wire, replace the relay.

As I mentioned, pry the cover off of the relay and look at the contacts. If they
are pitted replace the relay. You can manually energize the relay by pushing down on the contact plate.

 

[mark1952]

I'll try to explain how the circuit works.

In all blower speeds except High the voltage to power the blower motor goes thru at least one resistor.
The voltage/current flow from the Dark Blue wire passes thru the normally closed contacts of the Blower motor relay then to the Black/Red wire.

In High speed mode 12 volts from the AC fuse passes thru the Blower motor relay primary coil. The relay energizes and 12 volts from the Red fusible link passes thru the normally open relay contacts and then to the Black/Red wire. **************(The resistor network is not used in this mode). ************

If you manually jumped 12 volts from the Red wire to the Blower motor and it runs that proves the blower motor is good and the 12 volts from the fusible link is good.

It does not eliminate the resistor network or the Blower motor relay.

REMOVE/UNPLUG THE BLOWER MOTOR RELAY FROM THE SOCKET.

Turn the ignition On.
Set the C60 manual HVAC rotary dial to anything except Off.
Set blower speed to Hi
Set the volt meter to read DC
Red probe on the Brown wire at the relay socket
Black probe to Black wire.
Should measure 12 volts.
If no 12 volts verify the AC fuse is good.
If the fuse is good verify the Black wire at the Blower motor relay socket has zero resistance to the negative battery terminal.

If it does you should have 12 volts on the Black/Red wire going to the blower motor.

If no 12 volts on the Black/Red wire, replace the relay.

As I mentioned, pry the cover off of the relay and look at the contacts. If they
are pitted replace the relay. You can manually energize the relay by pushing down on the contact plate.

ecss!!

guess what!! it was the relay! it came in today and i replaced it...after a little prayer and the heater fan works on all 3 speeds.

I just wanted to thank you for all your help. i would have never found it if it wasn't for you and your persistence in helping me. you are a saint!!

thank you again for all your help. just one more thing i can check off my list.

a little history about the car...my dad purchased it for my mother in 1986. drove it right off the showroom floor. i have stored it during the winter months for him. he pasted away in 2009 from Alzheimer's after all my brothers and sister (12) did home care with my mother until he passed away at home. after that my mother told me that since i had taken care of the car for them she was going to give it to me. it sat for many years when he was ill. i had to have the trans rebuilt, the exhaust done, the cooling system flushed and also the fuel system flushed. the car runs great!! only has 42,000 miles on it. its a 86 convertible pace car and is black with the silver interior. all my brothers and sisters are jealous because of the great shape it's in.

at any rate, i believe I'm upside down with everything that I've done on the car but it's sentimental value is priceless. i will continue to work on it and restore it to is original condition. not going to modify anything. i only drive it on sunny days and then it goes back under the cover and in the garage.

i can't express the gratitude that i have for you with helping me with something that I've never tackled before. you are the best!!

Mark