Heater Control Valve Or A Cable?

lex4me · January 14, 2011

To bypass (or not) my heater core, I first have to change to full heat or full cold with the temperature up/down switches on the dash. Once I do so, I have to pop the hood and manually move what I think is the heater control valve at the firewall to the up or down position. The valve I am moving is attached to the cable that is certainly operated by the servo controlled by the dash module. The question is whether I have a bad cable or a sticking valve (is the cable able to be lubricated?).

If it helps, I cannot, for example, get the valve to move to provide heat in the cabin unless I first change the desired temp on the dash control to request it.

Any ideas?

billydpowell · January 15, 2011

All I can do is guess at what model you are having trouble with.....

you should be able to remove the cable from the valve, and work it both ways freely, if not, you have a bad valve, and yes you can lube the cable, slowly/slightly with a spray can. your cable should move (in reference to the temp you dial) in both directions.

good luck..

Vudugan · October 18, 2011

Long time lurker, first time poster, 93 Ls400. Figured I add to this post due to me having somewhat the same situation. NO HEAT. Changed thermostat, burped and come down to this so far. Thing is I can move the heater valve up and down with minimal force, this is telling me, in a sense, that the cable is not broken. A/C works fine but no heat. Heat was working awesome when I purchased the car back in April this year. So, when i have the heater valved turned all the way up I still get no heat, whether its up or down. I am in no way a mechanic but I do have the know how to replace whats broken. At this point I'm not sure whats broken. Please help!!

EDIT: Also would like to add, that when I manually lift the lever it will go halfway, not knowing how far up it should go. So it would be pointing toward the radiator vs up towards the hood. I can add a pic later today.

Again, is that as high as it goes? I will be popping off the cable in less than 2 hrs. just don't want to do anymore damage.

jaswood · October 18, 2011

To bypass (or not) my heater core, I first have to change to full heat or full cold with the temperature up/down switches on the dash. Once I do so, I have to pop the hood and manually move what I think is the heater control valve at the firewall to the up or down position. The valve I am moving is attached to the cable that is certainly operated by the servo controlled by the dash module. The question is whether I have a bad cable or a sticking valve (is the cable able to be lubricated?).

If it helps, I cannot, for example, get the valve to move to provide heat in the cabin unless I first change the desired temp on the dash control to request it.

Any ideas?

What you are doing, in effect, is providing "boost" for the servomotor that's trying its best to move the blend door and the water flow valve simultaneously. I would vote for the water valve to be sticking. You can pop the drive cable off of the valve and then see if the cable end moves freely up and down with a setppoint change from COLD to HOT.

Vudugan · October 18, 2011

Pulled cable off and got lever up more higher, I can now feel a bit of heat. I'm not sure how high lever actually goes. Would you mind posting a shot of yours so I can compare? On a bad note, as I played with temp settings, wire did not move up or down. I'll post another picture when I get in the house.

Vudugan · October 19, 2011

http://imageshack.us/photo/my-images/811/20111018183133329.jpg/

Vudugan · October 19, 2011

Not a bit of heat this morning.

jaswood · October 19, 2011

Not a bit of heat this morning.

One of your earlier statements seemed to indicate that it was easier to move the water valve to the HEAT position with the cable connected if the commanded setpoint was max heat, or both vice versa. That would imply that the servomotor was holding position in the opposite mode and/or was too weak to actually move to the new setpoint unless you assisted it. Since it still would not move on its own when disconnected from the water valve my conclusion would be that the blend door, reheat/remix routing vane, inside the plenum, is sticking.

Even moving the water valve manually to the HEAT position will be of little help if the blend door remains in the FULL cooling position.

Vudugan · October 19, 2011

I'm not the OP, originally when I attempted to move valve it was with minimal force still attached to cable. Can you give me an idea as how to get to the blender?