Help! Blower Continues to Run After Ignition is Off!

[71CajunVette]

Hey all! Not new to the site but first time posting.

I have tried to search this problem throughout the site but have not found the answer.

When I turn off the ignition on my 71, even if the blower is not on, the blower will turn on. To turn it off, I have to move the switch back and forth from off to high or even adjust the A/C controls before it turns off.

I have replaced the blower speed switch, the blower motor, the control module and resistor in the engine compartment but it has not fixed the issue. Control module to the left (plug near the two silver rivets) and resistor to the right (Chrome box).

Does anyone know of something else that I am missing? Is there another relay?

Thank you in advance to your attention to this matter.
Paul

 

[toobroketoretire]

That's a very common problem that is caused by the points in the relay sticking together. Replace the relay and your problem will be solved. About $15 I believe and readily available.

 

[71CajunVette]

Relay location

Can you tell me about where this relay would be located?

Thanks

 

[toobroketoretire]

Can you tell me about where this relay would be located?

Thanks

Your picture shows that relay. After many years of use the high speed points will get fused together and then the blower will continue to run after the engine is shut off. You can use a double-sided piece of 600 grit wet-or-dry sandpaper to remove the carbon on the points and they'll work as good as new again. Remove the cover and you'll see the points I am referring to.

 

[71CajunVette]

Relay/Resistor

Are you referring to the "chrome" box? That is new and was replaced. I improperly referred to it as a resistor.

Is there only one relay?

 

[Antz81]

Only the one relay. Since it's not the problem it sounds like the circuit may be picking up power from somewhere it shouldn't. When you play around with the speeds after the ignition is off, does it stay at the same speed? If the speed changes the the fault is before the speed switch. It may take a while to locate.

 

[71CajunVette]

Yes, the speeds change when I move the switch to each different speed.

I have a new speedometer coming in so while the dash is apart, I will try to track the wires going into the switch to see if I can determine the issue. Right now I have the control module unplugged which prevents the fan from coming on after the ignition is turned off but that means I can only use the fan on high. Seems to be the best option right now until the problem is determined to prevent the battery from being drained.

If any other suggestions from anyone..................I am all ears.

Thanks

 

[toobroketoretire]

Your new relay may be defective. Try tapping on the cover and if your blower turns off it is defective.

 

[Antz81]

Your new relay may be defective. Try tapping on the cover and if your blower turns off it is defective.

The relay only controls high speed. If it would only run on high speed this may be the case, but since the speed control works the relay is fine.

 

[71CajunVette]

I thought I read where you could disconnect the "hot" wire to the control module or the relay and that would prevent the fan from staying on after the ignition is off. Has anyone done this and if so, which wire and does it prevent something from working or causes a problem from not having constant power?

Also, when I had the center console out, just under the center bezel where it meets the gauge bezel, there appears to be a relay. Would this relay have anything to do with the A/C or blower?

 

[Antz81]

I thought I read where you could disconnect the "hot" wire to the control module or the relay and that would prevent the fan from staying on after the ignition is off. Has anyone done this and if so, which wire and does it prevent something from working or causes a problem from not having constant power?

Also, when I had the center console out, just under the center bezel where it meets the gauge bezel, there appears to be a relay. Would this relay have anything to do with the A/C or blower?

There's a couple of places you could disconnect it. But that would effect the blower while the car is running.

Not sure what the other relay is for, not likely to be related to the a/c or blower though.

 

[toobroketoretire]

I thought I read where you could disconnect the "hot" wire to the control module or the relay and that would prevent the fan from staying on after the ignition is off. Has anyone done this and if so, which wire and does it prevent something from working or causes a problem from not having constant power?

Also, when I had the center console out, just under the center bezel where it meets the gauge bezel, there appears to be a relay. Would this relay have anything to do with the A/C or blower?

The relay under the front/right of the center console is the wiper relay and the relay on the front/left is the power window relay. I replaced that power window relay with a 20-amp circuit breaker so I could power my windows up or down without having to turn the key ON.

Back to your problem: If that relay stays warm to the touch all the time the points have fused together which is very common for relays that handle a lot of amps.

 

[71CajunVette]

Thanks for the information regarding the relays under the center console.

I will check the relay again but it was just changed weeks ago.