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brian du4

Not Smart Enough To Figure Out Climate Control

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Hi, I'm a new owner of a 1995 Ls400. It is a very clean machine, inside and out, but being use to manual heat controls, this climate control is kicking my butt, or it's not working right...probably me not working right, instead of the car. Anyway, either in manual or auto, I am having trouble getting the heat to work. It does work, but I can't seem to get it to blow heat when sitting in driveway trying to defrost windows. When I turn on front window defrost in auto, the a/c kicks on, and never kicks off and keeps blowing cold air, even if I turn the a/c off. I put the temp on max heat, and whether in auto or manual, heat will not blow out of vents, just outside temp air. But the other day when driving, in auto it picked up and started heating the cabin, and maintaining temp. But as soon as I turn off, and drive later, the system seems to not want to blow heat, no matter what configuration I put all the switches in. Anyway, the owner's manual is not real helpful, I've tried it all...unless I am having a damper stick or something not switching to blow air across the heater core. Thanks for any help, I definitely need it, and only way to learn is to ask questions and ask for help.

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Look for the forum in the SC club about heater problems, seems like this happens alot, caused by a bad vacuum valve not drawing engine coolant into the heater core for the HVAC. And isn't it annoying with automatic climate control turning on AC when you want defrost? Manufacterers keep saying the AC will dehumidify the air, but in practicality plain hot air works perfect.

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Is the temperature gauge in the instrument cluster getting up to about the middle of the scale within a few minutes? Probably the most common cause of no/low heat from a car heater is a defective engine coolant thermostat.

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plus dont overlook the air bubble lock in your system... it can be a pain.. warms good while moving, but cools down at stops... search the forum, many different threads on this problem.

http://us.lexusownersclub.com/forums/index.php?showtopic=67395

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First off, WELCOME to the club, brian! :cheers:

As Jim mentioned... where is the temp needle pointing when you are sitting in the driveway trying to defrost? Is the engine fully heated? The needle should be about in the middle or slightly below when the engine is heated. Maybe you are just not waiting long enough?

Kevin, have to agree about the A/C. Seems like good old heated air does the defrost trick just fine. Always did on my old 60's vintage cars.

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The engine temp warms up pretty quickly, the needle goes to midrange, yet no matter how I switch and try different things, it continues to blow cool air, yet the only two times I have gotten it to work, was when I left the system in auto and the car was in motion...I left everything in the same position, so when I started up the next time it would pick up where it left off, but no luck. Being new to all this forum stuff, I am not for sure how to search other forums for this issue, and took me forever just to find these replies to my initial post. Maybe I should take the time to go through the welcome stuff, but adopting a fulltime granddaughter tends to take up a lot of time, so I am looking for simplicity in most things. Thanks for all your replies, though, it is greatly appreciated.

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Ok.. now, simple test. With the engine fully heated, idling in the driveway, temp controls set to "hot" and no heat condition, put your foot on the accelerator pedal and nudge the engine RPMs up to around 2500 and hold it there. Does any heat start to appear shortly thereafter?

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The engine temp warms up pretty quickly, the needle goes to midrange, yet no matter how I switch and try different things, it continues to blow cool air, yet the only two times I have gotten it to work, was when I left the system in auto and the car was in motion...I left everything in the same position, so when I started up the next time it would pick up where it left off, but no luck. Being new to all this forum stuff, I am not for sure how to search other forums for this issue, and took me forever just to find these replies to my initial post. Maybe I should take the time to go through the welcome stuff, but adopting a fulltime granddaughter tends to take up a lot of time, so I am looking for simplicity in most things. Thanks for all your replies, though, it is greatly appreciated.

I put a link in my post... take a look

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Thanks for the simple test, landar. I will have to wait and try that tmrw after church. I will post and let you know how it goes, thanks again. I will also click on your posted link, mr powell, tmrw when I have more time to read it.

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I tried your simple test, landar, and sure enough as I brought the rpm's up, heat started coming out of the vents, and as soon as it returned to idle, the heat went away. I'm assuming this is due to more vacuum at higher rpm's allowing the valve to open that sends hot coolant to the heater core. I sound like I know what I'm talking about, I really don't, but I just want to know what to tell my mechanic when I have him look at it. Thanks for any more help, it's appreciated!

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I tried your simple test, landar, and sure enough as I brought the rpm's up, heat started coming out of the vents, and as soon as it returned to idle, the heat went away. I'm assuming this is due to more vacuum at higher rpm's allowing the valve to open that sends hot coolant to the heater core. I sound like I know what I'm talking about, I really don't, but I just want to know what to tell my mechanic when I have him look at it. Thanks for any more help, it's appreciated!

Brian, the results point to the issue to which Billy Powell is referring. Mainly, an air lock in the coolant system. Read the thread that he included and you will have your answer. Actually that thread is a restart of this original thread -> http://us.lexusownersclub.com/forums/index.php?showtopic=67323

Basically, you need to "burp" (purge) your cooling system of air. A fairly simple thing to do. I would, however, put a new radiator cap on first because a bad cap can be a cause of not being able to maintain proper pressure and result in difficulty purging the air. You can try this yourself w/o a mechanic. Make sure that you only add the same type of coolant as is now in the reservoir as they are not all compatible. Let us know if this resolves your heating issue.

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I talked to my mechanic on the phone, and he said to bleed coolant system of air to let engine warm up, then keep around 1500 rpm for 4 to 5 minutes with the radiator cap off to bleed air out of coolant. After doing that, when the engine returned to idle, the heat stayed on instead of fading away like it normally does...i let car idle for about 5 minutes, and the heat stayed on the whole time, and i thought i had the problem solved. 2 days later I go out, start car up, engine temp warms up nicely, but once again no heat coming out of vents. I increases rpm, and sure enough the heat returns. I didn't try burping air again, I just got frustrated and shut engine off...so it seems like it will keep heat at idle, but only after I have run rpm's up for awhile...it will not put out heat at idle after starting the engine from cold condition. Radiator cap? Suggestions? Thanks, Brian

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Did you make sure the reservoir was filled to the 'Max' mark with coolant when the engine is cold? If you are low on coolant you could be sucking air back into the system when the engine cools off overnight. Hmmm, wonder if you have a cracked reservoir tank...(never mind just thinking to myself :whistles: ).

And did you make sure the heat was on the "HOT" setting to ensure the heater valve is fully open? The engine RPM should be more in the 2500 range, not 1500. (but don't rev it until the engine oil starts to warm...a few minutes after starting from cold).

Although not absolutely necessary, I have always had the front of my car up on jack stands (about 18 inches) when burping the system.

For the price of a new cap, I would certainly invest in one.

Give it another try, this time being VERY careful to observe ALL that has been discussed. Just one missed step could be all it takes.

Let us know the outcome.

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I agree about buying a new cap and also trying it one more time.

Hopefully you don't have a partially blocked heater core where the heated coolant is having trouble making it into the core at low RPMs.

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Brian, there is a bolt you can loosen to help get rid of air also,

this photo is when we put my timing belt and water pump on my old 97 LS,

should be the same as yours. you can see the black water outlet in the photo.

right above it is the bolt. I dont suggest you try this, but I ran mine with this bolt loose, not removed, but not tight. with my system filled and radiator cap on. ran it about 2500rpm and let the air and coolant seep out, I could see air bubbles coming out at first, then just coolant. tightened the bolt up, let it cool down and topped the reservior off, never a problem.

you might download this, print it and let your mechanic see it. I had a 7 stall garage for 30 years... so I know this works. not trying to be smart, just trying to help. click on the photo to enlarge it. next is my A in front of my Shop

post-5365-0-90348400-1292093086_thumb.jp

post-5365-0-44628300-1292101604_thumb.jp

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That is a good idea, billy. A lot of the 90's GM cars get burped in a similar manner. I notice the 97 LS has a hex bolt(looks like about a 17mm) rather than a 10mm Allen plug on the 98-00.

Nice Model A. Wish I was in TX right now. Snow and cold here. The good news is that I do not have to 'dream' about a white Christmas. Its here plenty early. All courtesy of "global warming" of course. :lol: ^_^

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That is a good idea, billy. A lot of the 90's GM cars get burped in a similar manner. I notice the 97 LS has a hex bolt(looks like about a 17mm) rather than a 10mm Allen plug on the 98-00.

Nice Model A. Wish I was in TX right now. Snow and cold here. The good new is that I do not have to 'dream' about a white Christmas. Its here plenty early. All courtesy of "global warming" of course. :lol: ^_^

Smile.... I have only seen snow on Christmas in Texas, two times in my 76 years... so I have to dream.

but I dont have to drive on it... and that is a good thing, I am the worlds worst.

what ever it takes to do it, is missing in me...

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I made sure coolant level high enough, which it was...the engine was up to normal range, and i had the heat on max...no heat on idle, but with rpm's up the heat came back...went back down to idle, and the heat slowly faded away...installed a new radiator cap, and tried next day, and still blows cold at idle...the only thing I didn't do was jack up front of car, I have a small one car garage, and really not feasible to do this...the only thing I have noticed is that my coolant level seems to never change, whether hot or cold, i don't know if that is tipping off a problem or not, just wanted to let ya'll know some other symptoms...if the hot coolant line that goes to the heater is the one that runs most of the length of the firewall, then that line feels warm as the engine warms up, but the warm coolant is not making it into the heater core...hot water valve to heater partially clogged or not opening unless rpm's high, or the heater core partially plugged as someone else suggested? Or still the possibility of air in system that needs to be further pursued, as billy suggested by bleeding air out the bolt in his picture? Thanks again.

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If you are getting a lot of warm air at 2500 RPM then I would doubt that your heater core is plugged.

So, next step would be billy's suggestion of purging by loosening the 17mm fill plug and again running the engine at 2500 RPM for a few minutes. You will need a helper to do this. Someone to rev the engine while you carefully loosen and retighten the bolt. Actually, if I was doing it, I would get the engine up to temp, then loosen the bolt very slightly...just enough to get some coolant trickling out. Have the helper rev the engine while you slowly crack open the bolt and watch for coolant leakage. If you get a spitting effect, you will know there was air in the system. Once you are convinced that the air is purged just tighten the bolt all the way and you are done. And it would not hurt to have an absorbent shop rag around the bolt area to soak up the overflowing coolant so it does not seep down into the engine timing belt area.

If this does not solve the problem, we move on to the heater valve.

Do you feel confident enough to try this?

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also.... dont you have any hills you can park on? I remember a "few" around there. your helper can even be your wife/girlfriend, just show them the tach. and loosen the bolt.

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Yea, I feel confident enough to do this, just have to wait for ice and snow to clear off roads enough to get the car out on a hill without getting stuck...I am a maintenance technician at a large automobile plant/factory, so I understand some on heat transfer, mechanical drives, use of lots of tools and so on, just no experience on cars, just experience on welding robots, conveyores, PLC's, motor wiring and controls etc...all the equipment used to build the cars. Will let you know how it goes, thanks.

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Yea, I feel confident enough to do this, just have to wait for ice and snow to clear off roads enough to get the car out on a hill without getting stuck...I am a maintenance technician at a large automobile plant/factory, so I understand some on heat transfer, mechanical drives, use of lots of tools and so on, just no experience on cars, just experience on welding robots, conveyores, PLC's, motor wiring and controls etc...all the equipment used to build the cars. Will let you know how it goes, thanks.

Well shoot...you're a natural to be working on cars then! You just need to build your confidence a little and soon you will be tackling bigger and bigger DIY'er jobs.

One thing I have been reading is that there seems to be a heater airlock issue on the 94-95 vintage LS that requires careful burping. The hill is a good idea but it might take the fill plug bleed to do the trick.

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Tried the bleeding thru the bolt trick, with not much luck it seems. Was done in my garage, not on a hill, roads too slick. I let engine warm up, put some towels under the bolt, had wife rev up to approx 2500 rpm, cracked open for a couple minutes and got a little bit of bubbles, not much, and then coolant came out after that. if I opened bolt too much then I guess it lost pressure, and nothing came out. Had to just barely keep bolt cracked for any flow of coolant to come out. Anyway, enough came out to soak two paper towels and some of a small rag. Heat went away as the rpm went back down to idle, well actually it stayed a little warm for awhile, so I shut it down, waited 5 minutes, went back out and at idle it blew cold air. Just so I get a better idea of the principle I am trying to pull off here, how does air in the coolant not allow the warm water to flow back into the heater core. There is pressure in the system, because I went to take radiator cap off after this, and it spewed pretty good...so if pressure is building up, shouldn't that be enough to force the coolant to take the lines to the heater core? Just asking and trying to learn. 25 years ago I was a nuclear plant operator on a nuclear submarine, so I understand heat transfer and theory, although things are slowing dimming away as far as the memory bank goes. Thanks for the help, though.

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You may not need to know this, but just ignore it if you dont need it.

pressure in a radiator is NOT used to move the coolant along, only the water pump does this. and there are several passages it can use, when you open the HCV the coolant has the opportunity to flow thru the heater core. IF an air bubble is in the core, it holds the coolant back until there is enough force (higher rpms)from the pump to push it thru. Pressure caps are designed keep the coolant from boiling at 212 degrees. your car is more effecient at 240 degrees.. to acomplish this the pressure cap... each pound of pressure raises the boiling point of the coolant by 3 degrees. so a 10 lb cap allows your coolant to operate at 242 degrees, and so on....

class over...

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See if this makes any sense...after bleeding air several times out of coolant, and still maintaining the same symptoms of good heat when I rev the rpm's up enough to increase water pump speed, which increases flow enough to push water thru the heater core, then the air leaves during the high rpm time, and then air pocket returns as speed decreases? to once again provide enough resistance to flow to stop hot coolant thru the heater core. Maybe I need to tell that air bubble to find another "happy place" besides my heater core so I can vent him back to atmosphere. I hope you understand I am just cutting up here, not trying to be sarcastic, gotta make fun of myself when an air bubble gets the best of me (just ask my wife, ha ha, get it?) Anyway, how hard to change the heater valve? I'm assuming that is next in line...when i troubleshoot at work, we go from the most common and easiest fix up the line to the next harder and so on. They don't look too expensive from the price I saw at "the parts bin", an online store. By the way, where is best site to buy Lexus parts, not necessarily OEM, but good aftermarket better priced parts? Thanks again for all your help, it is really appreciated!

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