1997 LeSabre heater won't turn off

[57corv]

I have the electronic climate control, not the manual. When I turn off the ignition, the lights on the heater controls light up and the blower comes on for about 4 seconds, and then turns off. About 20 seconds later the same thing happens. I tried pushing the off button but it still does the same thing. I tried disconnecting the battery for a minute but when I reconnect, it does it again. On for about 4 seconds, off for about 20 seconds.
Any suggestions?

[Tech II]

I never heard of that one before......have seen problems where you turn the car off and the blower motor continues to run on auto temp systems.....that is usually corrected with a blower control module.....

The fact your control head lights up when this happens, makes me think control head/programmer.....you would have to monitor the blower speed input to the blower control module, to determine this......

[57corv]

Now the off button comes on intermittently along with the digital display and the passenger side heater display in the door. Only for a second. Occasionally the blower motor comes on for just a second or two.
My guess is that I have a bad heater control module. I shudder to think of the cost at the dealer parts counter.

[brcidd]

See if it times out-- they made aftermarket "after-blow" modules to attach to blower motor to dry out the evaporator after the engine has been shut off- Maybe yours has one- usually ran for 1 minute every ten minutes for about an hour....Heck- Cadillac even had it so you could program afterblow into your ECM if the owner complained of mildew out of the vents.

[57corv]

I'll check that possibility also.
I decided to see if I was getting good connections at the programmer. I was able to get the main connector and the passenger valve actuator at the top off. I can't figure out how to get the vacuum harness connector off. I removed the little hex nut but the connector does not want to budge. I sprayed some electrical connector cleaner on the connectors I could get off. How does that vacuum harness connector come off?

[brcidd]

That vacuum connector is famous for plugging up- the nipples under it turn to gum- It is supposed to just pull off- but you'll probably destroy it to pull it apart. I've bypassed 5 or 6 of those due to vacuum not working right- I'd avoid it- besides it just tells the air where to come out- doesn't affect blower motor- your blower motor runs off the module in the HVAC case under hood under relay center.

[imidazol97]

Originally Posted by 57corv

I'll check that possibility also.
I decided to see if I was getting good connections at the programmer. I was able to get the main connector and the passenger valve actuator at the top off. I can't figure out how to get the vacuum harness connector off. I removed the little hex nut but the connector does not want to budge. I sprayed some electrical connector cleaner on the connectors I could get off. How does that vacuum harness connector come off?

The first thing I'd do is go to the Blower Control Module (BCM) on top of the blower channel on the firewall under the relay center. You can take out two screws that hold the relay center in place and move it up to get at the two screws. I'd disconnect the BCM and see what the unit does. The BCMs go strange. On earlier models they were notorious for turning on the blower when the key and all was off.

[57corv]

OK, You have given me some things to check. I didn't suspect the blower module. I figured the problem must be in the programmer.
The car has 157K miles. It had belonged to my wife's father and she got it when he passed away in 05. She doesn't want to sell it because of sentimental feelings about it and that it is comfortable riding.
I have been pushing the Off button on the dash when I park it. The blower motor seems to run less than if I just left it on Auto. Overnight, I disconnected the battery in case the blower motor ran it down.

[brcidd]

The after-blow option is explained is TSB 99-01-39-004B and includes your car...

[Tech II]

I did not think of the after blow module aspect.....like I said before, the only thing I ever saw was the blower just would not shut off, and would kill the battery, and this was fixed by replacing the blower control module(in some rare cases, the blower motor had to be replaced also, due to spikes caused by the motor which would take out the new blower module)......however, like I said, I never saw one cycle the way you describe it....

If you are driving along, and use your defroster, which may or may not turn on the Compressor due to ambient temp, and then then say after 5-10 minutes, while driving, you turn the system off, does the blower stay off?

If it does, when you come to a stop, and then put it in park, with car running, is it still off?

Then, when you remove the key, is that when the blower comes on?

If yes, then this could have something to do with an after blow module setup(this is not the same thing as a blower control module).....I'm not sure on this year model, if they actually put in an afterblow module, OR if they could just "program" it into the system.....I know in the newer vehicles, they could program it into the control head/programmer.....in older cars, they had to add the afterblow module.....

The afterblow module was used to turn the blower motor on, when the car was shut off, in high humidity situations......there would be condensate left on the evaporator, and this would breed the growth of bacteria, which would create a sort of "fungus" smell when you would turn the blower on......with the blower motor running a few minutes after the vehicle was shut off, this would "dry out" the fins of the evaporator, preventing this growth....

[57corv]

Tech II:
I will try your suggestions today if possible. This morning, after having the battery disconnected overnight, I took it to church. Before I turned it off, I decreased the temp and pressed the Off button. When I came out, the battery was dead and I had to get a jump. When I got home and turned it off, everything stayed off for 5-10 minutes. When I came out to the garage again, the blower motor was running strong again. I disconnected the battery.

[brcidd]

If it were mine- I'd replace the blower motor module- under the relay center- It is expensive- about $120-$160- but you can get a used one on-line for maybe $30

[57corv]

Problem is fixed. It was caused by bad corrosion at a 6-wire connector in the right rear corner of the trunk. A large 3" by 3" rust hole had developed in the right rear wheel well due to all the salt they spread on the roads up here. Water (and salt) had splashed into the inside and behind the trunk panel so I was not aware of it. The water had run down the wiring and caused the corrosion at the connector. This connector supplied power to several components and current was bled off due to the corrosion. I was not aware that power was present when the ignition was off.
Anyway, thanks to all of you who made suggestions on where to look. Sometimes diagnosis is hard to do over the internet.

[Tech II]

Glad you got it fixed...however the fix is confusing, since the blower motor circuits have nothing to do with the rear....

What does go back there is the circuit for the rear defogger from the control head......however that wiring does not go into the trunk area......

Only harness I can think of in that area may be a harness connector to a power antenna or to the lights.......

[imidazol97]

Originally Posted by 57corv

Problem is fixed. It was caused by bad corrosion at a 6-wire connector in the right rear corner of the trunk. A large 3" by 3" rust hole had developed in the right rear wheel well due to all the salt they spread on the roads up here. Water (and salt) had splashed into the inside and behind the trunk panel so I was not aware of it. The water had run down the wiring and caused the corrosion at the connector. This connector supplied power to several components and current was bled off due to the corrosion. I was not aware that power was present when the ignition was off.

I don't think of anything back there which has power with the key off, either.

The only odd circumstance I come up with is that there was power on a line that was grounding there, and that caused the battery voltage to drop below the minimum for the various computers/modules and that one of those modules was in the programmer or the BCM and caused the odd behaviors. The BCM has power with key off and so does the programmer for the memory I assume.