Water Mix Valve Servo/Cable

[Douglas S]

Heater has worked fine all winter.

Went to use it a couple of days ago, and only received cold air. Cable is not moving water mix valve on firewall. In fact, cable is not moving at all (I can't even move it with vice grips on the end).

I can hear the servo actuate in the dash. I started taking the dash apart to investigate only to discover that it is completely buried, meaning the entire dash would have to come out to access it.



Should I order up a heater core, servo, and cable and say goodbye to a weekend or is there something I'm missing? Unfortunately for me this doesn't seem to be a common issue.

 

[western flyer]

If you are saying that the cable does not move on the heater valve under the hood (or if it turns out to be the case that the heater valve has failed/jammed), then you may just need to change out the heater valve. They get old and brittle regardless with age, so if yours is original, then it is time. With a heater valve in hand you can change it out in an hour or so (30 minutes if you are somewhat speedy), and potentially save your weekend.

 

[Douglas S]

Cable doesn't move at all, even disconnected, and even if I use pliers to pull/push.

 

[Douglas S]

For anyone with this issue, the servo that controls the water mix valve is located almost directly behind the radio in a RHD HDJ81. The same servo controls the flap to regulate the upper dash vents.

I was able to get everything going by using some long needle nose pliers to disconnect the cable at the servo end and then work it back and forth, spraying penetrant in the engine end of the cable periodically.

 

[80SeriesJunkie]

where is the servo??

 

[knuckledragger80]

I just did a cooling system overhaul and the rear heater bypass. Front heat wasn’t working either and I just replaced the heater valve. Turns out I didn’t account for the position of the cable relative to the servo controls at the dash. Hopefully it’s an easy fix like that for you. Had the valve closed with the tstat set to coldest but no ac, fought to stretch the cable to the retainer and make sure the plastic sleeve is clipped into the little semi circle part of the clip to hold it securely. Now I throw it into heat and it works.