Climate Control Blower Suddendly Slows Down

[joedoro]

94 LS 400 128k miles that I bought 9 years ago with 35kmiles. It has developed the black time/temp panel and both dash issues and are at the point where I will address them. However, last winter it developed a problem with the climate control blower suddendly going to the low sped despite what buttons are pushed or where the temp is set. Then after coming to a stop the fan will sometimes go to the appropriate speed only to drop down to the low speed again when the gas is stepped on (mainly during acceleration but sometimes reving while stopped). This only happens when it is cold enough for the heat to be on not when it is hot and the AC is needed and cold air is being dispensed.. For example no problems last summer but as soon as it cot cold this winter it started doing it again.

Planning on replacing the LCD but don't want to do this if if this is an indication of the unit itself going bad.

thanks

[Econ]

Wow - kind of confusing. It sounds like normal operation in that it's targeting a temperature and slowing the flow of air, but you say that it doesn't matter if the climate control is on "auto" or not? And there aren't any problems when you use A/C?

It sounds like the heater core on your car may be going bad. Stepping on the throttle or accelerating creates more heat than just engine idling, and that heat is transferred via the coolant into the heater core. Increases in the coolant temp will blow more heat into the cabin, which will cause the climate control to reduce the fan speed to compensate. Once the coolant is at a lower temperature, lower heat output = increased fan speed.

This is all assuming, of course, that the "Auto" selection is on. If that's not the case, I'm baffled. Usually a fan will slow down while idling and then speed up while accelerating/revving - it has to do with the electrical system.

[flanker271]

I have the same issue on my 92, and I never have the auto on. The fan blow very little air in the "med" setting, and at high setting, I can hear the fan turning rapidly due to the whirling noise but there is still hardly any air coming from the vents. I also noticed that the fan will speed up a bit when accelerating, and slowing down while idling.

[914lps]

Is the fan speeding up as in you can hear it changing speed or are you feeling more air when you speed up. If you are only feeling more air, and the vent is set for outside air, you get more air becouse the cars speed is pushing air into the car.

Is there any diferance in air flow fan speed when in park and you rev the engine or just incress the rpm and hold it at say 2,5 rpm for a few????

[mehullica]

Check out the blower motor linear controlller (resistor). Sounds like it's going bad

[joedoro]

Thanks for the feedback -

To clarify a little :

Doesn't matter if auto button is on or off, or if high, med or low is set for the fan speed, it's as if it's defaulting to low fan speed. The temp of the air that is coming out is hot.

Works appropriately when it's warm and the AC is operating with the fan speed slowing up or down as you would expect as the temp in the car changes.

Over the years I've noticed that the fan slows a bit when you come to a standstill and are at idle and then will speed up as the gas is depressed to start, which I have assumed is normal. In the present case however, it seems to be at the point of just starting to accellerate that instead of the fan speeding up again it just goes to low speed and will stay there only to resume the appropriate fan speed when I again come to a stop.

Again thanks