Originally Posted by Drizzle66

I've searched pretty extensively and found several posts that are ALMOST the same as my problem -- but not quite...



My '96 LS400 runs very well and is well maintained. But I've noticed that when I go on a long trip (two hours or more -- it usually takes quite a bit more than that), my heat or A/C airflow fades and eventually quits blowing. It's not a coolant level issue -- it does the same with A/C as with heat. (And it's an AIR FLOW ISSUE, not the temp of the air...) Different RPMs or engine load don't make a difference either. And I keep the cabin air filter changed regularly, so it's not that. In order to get the air-flow control back, the car has to sit for a period of time (sometimes stopping for lunch will make it 'all better', and sometimes it requires an over-night stop).

Just driving around my normal daily life, it never happens -- so of course, I can never get it to my mechanic while it's acting up because I have to be several hours from home before the problem ever shows up!

It would be my guess that the problem is located in a control that directs an airflow 'door' somewhere. When the problem occurs, you can hear the fan running as normal (responding aurally to manual adjustments in fan-speed). But the air simply quits flowing from ANY of the vents. The air always comes from the correct ports (defrost, face, feet) when it IS flowing. But when the problem surfaces, the air-flow simply tapers off to nothing.

It's really maddening since this car is my preferred driver, and it's BEAUTIFUL for long trips -- except for this! If it's during the need for A/C, it's merely an inconvenience, as I don't mind driving with my windows down for a while. But when it's cold out (like on our trip home from our daughter's place more than three hours away last night), it can become a hazard, since I have no way to provide ANY airflow to the windshield, and keeping the windows from fogging up or even frosting over can become very challenging. (Especially with two adults and two dogs in the car, like I had last night...)

Anyone else every experience this? With winter here, I really need to find a way to address this. But since I can never experience the problem except when I'm a few hundred miles from home, it's never practical to examine things while it's acting up!

Thanks in advance for any advice or shared experience...
Dennis

Originally Posted by Drizzle66

I've searched pretty extensively and found several posts that are ALMOST the same as my problem -- but not quite...



My '96 LS400 runs very well and is well maintained. But I've noticed that when I go on a long trip (two hours or more -- it usually takes quite a bit more than that), my heat or A/C airflow fades and eventually quits blowing. It's not a coolant level issue -- it does the same with A/C as with heat. (And it's an AIR FLOW ISSUE, not the temp of the air...) Different RPMs or engine load don't make a difference either. And I keep the cabin air filter changed regularly, so it's not that. In order to get the air-flow control back, the car has to sit for a period of time (sometimes stopping for lunch will make it 'all better', and sometimes it requires an over-night stop).

Just driving around my normal daily life, it never happens -- so of course, I can never get it to my mechanic while it's acting up because I have to be several hours from home before the problem ever shows up!

It would be my guess that the problem is located in a control that directs an airflow 'door' somewhere. When the problem occurs, you can hear the fan running as normal (responding aurally to manual adjustments in fan-speed). But the air simply quits flowing from ANY of the vents. The air always comes from the correct ports (defrost, face, feet) when it IS flowing. But when the problem surfaces, the air-flow simply tapers off to nothing.

It's really maddening since this car is my preferred driver, and it's BEAUTIFUL for long trips -- except for this! If it's during the need for A/C, it's merely an inconvenience, as I don't mind driving with my windows down for a while. But when it's cold out (like on our trip home from our daughter's place more than three hours away last night), it can become a hazard, since I have no way to provide ANY airflow to the windshield, and keeping the windows from fogging up or even frosting over can become very challenging. (Especially with two adults and two dogs in the car, like I had last night...)

Anyone else every experience this? With winter here, I really need to find a way to address this. But since I can never experience the problem except when I'm a few hundred miles from home, it's never practical to examine things while it's acting up!

Thanks in advance for any advice or shared experience...
Dennis

Originally Posted by serverrack

I realize this thread is ancient, but I wanted to contribute some new clues for anyone else with this issue.

My car has these exact symptoms. I found that removing the cabin air filter cover while the system is running instantly restores air flow. (My filter is new)

Here’s the strange part: When I put the cover back in place, the air still flows… for a while.
This indicates an intermittent intake blockage. Removing the cover allows air to flow directly into the blower through the air filter access opening.

So, the question is; why does the air flow stay strong once the cover is in place? My theory is that the air filter is jiggled just a bit and that changes … uh … something?

The point is that in my case there is an interruption to the intake somewhere just above the filter in the air box itself. I’ll post an update if I can find what that is.

Originally Posted by RioBravo

I am trying to figure this out for my 1999 LS400. My air flow was weak; The fan sounded like it was struggling to blow. I found out how to change the Cabin Air filter and did it. For a day or so air flow was decent. Then it stopped completely. No fan noise. No air flow. If anyone has a suggestion of what to check please let me know. No AC and our temps are at or over 100 daily.