Potential Heater Valve malfunction????
08-08-10, 10:39 AM
#1
Pole Position
Thread Starter
Potential Heater Valve malfunction????
Hey Guys,
So my dad's 1992 LS400 has been having a heater issue for the last year but really only causes problems in the winter. The heater only blows warm/hot air if the car is driving over 40mph but as soon as he comes to a stop or speed drops below 40mph, the air becomes cold again. It's really a problem for my parents (they're in their 70's now) during the winter up here in the PNW and I want to try to figure out the problem and fix it before the next winter.
First off *I USED THE SEARCH FUNCTION* and found some useful information to begin the diagnosis. I began by starting the car from a cold engine and set the temperature to 70* and watched the heater valve to see if the valve would move as the engine reached operating temperature. As the engine reached operating temp I noticed the valve never moved and the fan continued to blow cool air, so I added a couple degrees at a time until I reached 84* and it STILL didn't move nor did the air get any warmer. However...as soon as it reached 85* the valve moved ALL the way up and the air was blowing hot!
Now...does this mean the HEATER VALVE is bad, or does this mean the SERVO MOTOR under the dash is bad?? There was no coolant leak around the valve and doesn't appear that there is any corrosion around the cable either.
I'd like to replace the correct part(s) but would like to refer to the experience from the CL gurus before I start replacing random parts!
Many thanks in advance, both from my father and myself!!
~Jonny
So my dad's 1992 LS400 has been having a heater issue for the last year but really only causes problems in the winter. The heater only blows warm/hot air if the car is driving over 40mph but as soon as he comes to a stop or speed drops below 40mph, the air becomes cold again. It's really a problem for my parents (they're in their 70's now) during the winter up here in the PNW and I want to try to figure out the problem and fix it before the next winter.
First off *I USED THE SEARCH FUNCTION* and found some useful information to begin the diagnosis. I began by starting the car from a cold engine and set the temperature to 70* and watched the heater valve to see if the valve would move as the engine reached operating temperature. As the engine reached operating temp I noticed the valve never moved and the fan continued to blow cool air, so I added a couple degrees at a time until I reached 84* and it STILL didn't move nor did the air get any warmer. However...as soon as it reached 85* the valve moved ALL the way up and the air was blowing hot!
Now...does this mean the HEATER VALVE is bad, or does this mean the SERVO MOTOR under the dash is bad?? There was no coolant leak around the valve and doesn't appear that there is any corrosion around the cable either.
I'd like to replace the correct part(s) but would like to refer to the experience from the CL gurus before I start replacing random parts!
Many thanks in advance, both from my father and myself!!
~Jonny
08-08-10, 05:50 PM
#3
Pole Position
Thread Starter
Hmmm...well forgive my ignorance, but what will disconnecting the linkage accomplish? The valve does indeed function, just not incrementally....only when the heat is on the highest setting. In other words, the valve will only open at the highest setting (85*) but on every other heat setting the valve sits closed. Are you suggesting anytime there is a desire to change heat settings that we pull over on the side of the road to adjust the valve??? I'm sure that's not what you're intending to suggest....could you elaborate a bit??
Thx!
Thx!
Thread
Thread Starter
Forum
Replies
Last Post
jonny2k
LS - 1st and 2nd Gen (1990-2000)
11
11-16-10 10:41 AM
