jnew911

96 ls400, 295k. I have done lots of searching on this one but hoping for some insight. Here is the history but I don't know if it is relevant to the current issue. My son is driving the car. Heat was only hot when car was at higher revs. This went on for a couple months then awful noise began and weeping coolant from front of engine. I figured this to be water pump and assumed the heating issue was from water pump too. It was about time for timing belt so I changed timing belt and water pump. It went great thanks to all of the threads I went thru. I did end up with a large washer left over when I finished and thought it would not matter. Wrong! It was the washer that goes behind the timing belt tensioner pulley. Without that washer the timing belt did not tension correctly so I had to take it all apart again. Luckily I was smart enough to figure out where the washer went even though I had been dumb enough to leave it off. Timing belt tightened up nicely this time and runs great. It took me an extra drain and fill to get the air out of the cooling system. Now running with no overheating.
Now to the heating problem. No heat now. And I mean no heat. Not when the car is at high revs or idle. No heat coming into cabin. The air control valve is not opening at all. A/C works fine. I read some threads about people getting under or behind glove compartment to servomotor. I'm thinking this may be my problem. The vents will change from floor to dash to defrost but no heat anywhere. Also, I don't hear any noise when I turn the system on. It seems like I used to hear a noise like a door opening or closing in the lower dash when I turned it on in the past. Now no noise of anything like that. Blower is working fine. Also, I can pull the air control valve open with my hand and close it and there does not seem to be any resistance on the cable. Even when I open it manually I get no hot air in the cabin. Is it normal for there to be no resistance on that cable on the air control valve?

LScowboyLS

I read a thread somewhere here in the last year where someone had this same issue and seems like something came unhooked or broke up in the area near the evaporator case

I may hunt for that thread in a while, I don't remember the title.

jnew911

Thanks cowboy. Where is that evaporator case. I saw some threads where someone took off the area under the glove compartment and got to what I think was the called the servomotor. They were able to clip that wire back on I think. Do you know offhand if it is normal for me to be able to open and close the air control valve with my hand without there being much tension on that wire? I mean I was thinking that normally there would be too much tension on that cable for me to move it with my hand.

LScowboyLS

yes, that is the area I am thinking of and may even be the thread I am recalling

jnew911

Well I have the glove compartment off but I don't think the cable that goes to the heater control valve is on the passenger side of my car. The post where that was is a 94. I don't see it anywhere on the passenger side of my 96. I read in someone's post that it is on the drivers side so I think I will look there next. There is a motor on the passenger side that moves a couple of levers and changes the air from the floor to the dash and defrost. This motor is working fine.
I still think this is strange. The heater control valve looks fine. I don't see a leak or anything. But, it doesn't move at all when heat is turned on. I can move it manually with my hand to open position but still get no heat! Weird to me. I am hoping that the cable is off on the other end and I can find it and that it opens another door and that is why still no heat even when it is open.
Again, all blowers are blowing, A/C works. I am think I am going to try to flush the heater core with water also.
Oh, I noticed that drs23 had some similar issues so I sent him a message to see if he has any insight.

jnew911

The motor that operates that cable is on the drivers side. Sure enough, that cable is disconnected from the motor. Not sure if the cable broke or lost a clip or both. Not sure how I'm gonna attach the two back together and may need to get a new cable.

randal

Seems strange that the heater quit when you were no where near it when changing the timing belt. I kinda suspect it might be as simple as an air lock in the heater core.

When you got the engine back together and added coolant, did you run the engine at about 2k RPMs for about 5 minutes WITH the heat on full blast (HOT) in order to refill the heater core? If not, you may now be pretty low on coolant and have a severe air lock in the heater core which would just require topping the reservoir off and doing the purge again.

Aeok18109

Air in the system for sure. Rebleed that thing dude

LScowboyLS

see if you recognize the motor/cable in this diagram: (click for larger view)

jnew911

The heat wasn't working before the timing belt change either but I thought it was because the water pump was going out. Water pump was out for sure. It was leaking coolant from front of engine and making a terrible noise. I thought the pump wasn't strong enough to get coolant to the heater core. But, after installing new water pump heater still isn't working. I did have an air lock but got it out now because I let coolant out and refilled again. I have not gotten low on coolant at all. Plenty of coolant in the system. My heater control valve is not opening at all. This cable was not attached to the motor under the driver side dash that is supposed to move the cable to open the control valve. It has to be fixed to operate. Cable must be connected to the arm on the motor. I think it lost a clip that attaches to it. Only thing that doesn't make sense to me is that the heat doesn't work even if I open the valve by hand. I will fix the cable first and then see if I have heat.
Thanks for the diagram, Cowboy. I was looking for something like that but I don't see the cable on the diagram. It runs from the heater control valve under the hood through the firewall and into the servo motor on the driver side under the dash. I don't see the heater control valve on that diagram either. I have a 1996. I am still looking at the diagram because it sure looks like it should be on there. i will re post if I see it on there.

jnew911

87106B may be the motor but I can't make out the cable on the diagram

LScowboyLS

those little servo damper motors are $132 at discount at the dealership, so I would be finding that cable clip! - lol

jnew911

Just found something on the internet that said that if the heat doesn't work when the heater control valve is opened manually then the heater control valve must be replaced. http://www.justanswer.com/uploads/sn...57_ls_heat.pdf
I think this makes sense because the heat should work with it open.
I'll just be glad if it is not the heater core. The control valve is $102 online. Wonder what the dealership wants for that puppy?

jnew911

Took off the heater control valve today. Ran water through it and it functions as it should. So, I took the hose off of that exits from the heater core, hooked up my water hose and flushed out the heater core with water. Put the heater control valve back on and viola! The heat is now working.
It still seems to cool off sometimes when idling but most of the time it is working and is very hot. The heater core was clogged. I put the cable back on the motor with a clip I bought at the hardware store. However, the clip isn't long enough. That or the cable is no longer long enough. I think I need about another 3/4" or so. But, for now I am driving with the control valve wide open so that heat will work. I don't guess it would hurt anything to just leave that valve open all of the time.
I'm still gonna try to get that cable fixed somehow.

sha4000

iTrader: (1)

Good to see when someone works their way through all the trouble shooting steps to figure out what is causing the problem.