98 LS400 automatic climate control
01-26-11, 09:19 AM
#1
Driver School Candidate
Thread Starter
98 LS400 automatic climate control
The automatic climate control in my 98 LS400 is getting wonky. I'm thinking the problem is with the doors/valves that control the airflow, but not sure.
What happens is that sometimes when it clearly needs hot air, it blows cold. Usually turning it off and back on again several times in succession "fixes" it on the fifth to tenth attempt.
I tried turning up the set temperature and that made no difference even when I have it all the way up on HOT. In my opinion that eliminates the thermostat as the cause since at that setting it should be blowing hot air no matter what the ambient conditions, though I'm not sure.
It usually happens after the car is warmed up. On a cold morning when I start it for the first time, it works as it should -- no blowing until the engine warms up, then blows hot/warm air. But after a while it starts blowing cold air when it should either be not blowing, or should be blowing warm air to boost the temperature a little bit.
And if I shut the car off for an hour or so and come back to it, so it has residual heat (water temp gauge is at say about 1/8) but isn't totally warmed up, it will start right up blowing cold air which remains cold even as the engine heats up (as measured by the water temp gauge getting to 1/2). That's when I start hitting the on/off button repeatedly until it gets it right.
These things make me think maybe the doors/valves that control airflow are getting stuck or not working properly. Has anyone else seen this and if so what was the fix? Any informed opinions are welcome.
What happens is that sometimes when it clearly needs hot air, it blows cold. Usually turning it off and back on again several times in succession "fixes" it on the fifth to tenth attempt.
I tried turning up the set temperature and that made no difference even when I have it all the way up on HOT. In my opinion that eliminates the thermostat as the cause since at that setting it should be blowing hot air no matter what the ambient conditions, though I'm not sure.
It usually happens after the car is warmed up. On a cold morning when I start it for the first time, it works as it should -- no blowing until the engine warms up, then blows hot/warm air. But after a while it starts blowing cold air when it should either be not blowing, or should be blowing warm air to boost the temperature a little bit.
And if I shut the car off for an hour or so and come back to it, so it has residual heat (water temp gauge is at say about 1/8) but isn't totally warmed up, it will start right up blowing cold air which remains cold even as the engine heats up (as measured by the water temp gauge getting to 1/2). That's when I start hitting the on/off button repeatedly until it gets it right.
These things make me think maybe the doors/valves that control airflow are getting stuck or not working properly. Has anyone else seen this and if so what was the fix? Any informed opinions are welcome.
01-26-11, 12:45 PM
#4
Pole Position
I don't think turning it on and off has anything to do with it except the time it takes to do it 5 or 10 times. 
It definately sounds like air in the system. If you're worried about the doors not opening or getting stuck, just listen when you hit the controls, you should hear the servomotors working. (very soft) Bleed the cooling system and you should be all set.
It definately sounds like air in the system. If you're worried about the doors not opening or getting stuck, just listen when you hit the controls, you should hear the servomotors working. (very soft) Bleed the cooling system and you should be all set.
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