hamah

I was having a problem with hot always coming from the center vents and passenger foot well. I took a look at the servos and sure enough 1 of the 2 temp mix servos was not actuating. For some reason it started to work (possibly a bad wiring connection got fixed) as I played around in there.

Now I have a different problem in that the fan speed control seems to only activate the blower if the temp setting is to full cold. Any movement towards warmer temps causes the fan to shut down.

In addition the defrost will only blow for about 2-3 seconds and then needs to have the button released and pushed back in before it will work again...for 2-3 seconds.

Interestingly if the fan speed control has activated the cabin blower when the defrost cuts out the cabin blower also stops and won't blow again until the defrost button is released.

If I do these actions with the engine off so I can hear servo activity I can hear servo actuation. I think this is weird because the defrost button should not be controlling any servo, only the defrost blower. I should also point out the the 2-3 second time of the defrost blower working and the similar time required to reset it seems coincident with the sound of the servo actuation.

I'm thinking I have a problem with the control unit itself but I'm looking for other troubleshooting steps before replacing it.

Any ideas? Better yet, anyone with a spare control unit they want to lend me for troubleshooting or sell at a reasonable cost?

mojorizing

Your problem with the cabin blowers could be caused by a non functioning rear blower. Does the rear blower work? Check the fuses, etc. Search rear blower" in the forum and you'll get a lot of info. The rear blower needs to work for any setting above the blue dot on the temp. control.

hamah

Thanks for the tip. I'll check it out and get back.

tbennett017

The defrost servos will actuate with the defrost button selected, as it is designed to go full defrost (vents set to the windshield vents + full fan) This sounds normal to me.

You most likely have a rear fan resistor problem, and the CCU is shutting it down as a failure mode. Check the fan resistor that is in the rear blower tube. Those can fail too. Its a springy thing that is inserted into the rear blower tube on the Left side of the engine bay... it runs from the heater box connection up past the distributor/coils and up to the rear blower fan.

martin964

hello,
its definately the rear fan (left side of the engine bay) not working for whatever reason. mine started doing the exact same thing and I found that a cennector had been left unconnected down the side of the heater fan tube. I connected this but then found that my fan wiring connector was the issue. To test he rear fan, turn the ignition on, and the haeting off the blue dot (say 20 to be sure), the check the connections on the fan wiring and make sure all other wires are connected. If none of this gets a reaction from the fan, (which should cut in), then check the resistor in the heating tube as this may be failed as suggested by other here. hope that helps!

hamah

Thanks for all the tips. The weather is great and I'm back home from the road so I plan to check out the rear fan but I really don't know what a normal condition is supposed to be and how to test for it.
-is the rear fan on all the time? only when warm? just when the fan switch on the dash is turned on?
-when operational will the sound be easily heard or should the engine be off?
-what is the best way to check the resistor?
Any other tips would be appreciated and thanks again for all the great advice.

hamah

BTW. All the advise on the rear fan was spot on. After researching the crap out of how and when the rear fan worked I took a look only to find the wiring connector to the fan had disengaged. A minute later and all was back to normal.

I love the knowledge base that the posters here represent. A lot of time and money is saved by all of us every day as a direct result.

I only hope that someday my contributions are as valuable to someone else.

Thanks all

SilvA4Q

Do you have any idea how you were able to get the vent from always pushing warm air into the cabin? I am having the same problem you started with. As soon as the car starts the vents start blowing air, even if its set to off on the ccu. The ccu works perfectly otherwise, all of the servos work accordingly except for blowing air through the vents when the ccu is off. Does it appear that there is an issue with the ccu or more likely the servo controlling the "off" position?

jimq

that sounds like a servo. Mine did that and I replaced both with used and it works perfect again.

SilvA4Q

were you able to tell that the servos werent working by looking at them with the cover removed? Should I be able to notice anything when changing the setting from 1 down to off?

jimq

you can see them move when you change temperature. Have someone move the switch while watching under the cover in the trunk.

bcr4d

I'm having the exact same problem as you were, even replaced the motor inside the blower. After I replaced the motor it worked fine for a couple days, now I'm back to blower working only on blue dot. How many connections are there to the blower motor. Is there a separate connector for the fan?

Foxman

I didn’t want to start a new thread, so I’m bumping this old thread with my quandary. The symptoms: I have heat coming out of both the center and right side vents, despite the thermostat being set to cold with the fan off. The right side door sill is also hot.

I checked the connection from the elbow pipe in the door sill to the heater ducts in the cabin, and all looks good and tight. No. 2 and 4 servos both appear to working correctly as well. Is it possible that the duct inside the sill has a loose connection? Bad seal somewhere above? I’m stumped. FYI I deleted the rear blower fan, so no issue there. Thanks in advance. for your thoughts.

gregmitch

Have you checked your heater flapper box? I had this same exact issue and my passenger side heater flapper box was stuck open so hot air from the heat exchangers wasn't getting dumped. I did a temporary seasonal fix and disconnected the heater tube and sealed off the heater flapper box and now I don't get hot air coming into the cabin when it's set to cold.

Foxman

Thanks for your reply, I will double check the flapper boxes. I disconnected both ducts from the heat exchanger about a year ago when I had another heat issue, and both flappers were functioning at the time. If the right flapper box is still working, I will plan on disconnecting the right duct again until I can get this sorted. Thanks again.