Rep Power: 0

I have a 99 Civic HX and the heat is not working in it. It blows air out but it doesn't get hot or even change temperature. It is full of coolant, I flushed the heater core, and changed the thermostat but it still doesn't get hot. I noticed that the heater contol cable that opens and closes the heater valve on the firewall doesn't move when you adjust the heat from hot to cold. I took the cable off and adjusted to the valve manually making it fully open and fully close but the air still didn't change temperature. Now I am all out of ideas so if anyone could help I would really appreciate it. Thanks.

 
Rep Power: 518

You said the cable didn't move.....

That might mean the temperature door (air mix) actuator isn't moving either. It's attached to the bottom of the heater case, toward the passengers side...

Has linkages, cable attaches there too.......

You might try a push/pull on the linkages while twisting the temp ****, see if a nudge will get it started moving again.....

There are electrical tests you can do for it, you need some good service manual info for it.

The heater control panel can do some self-diagnostic stuff, there is a "button dance" to enable the tests. You would need a good service manual.


HTH

 
Rep Power: 0

I couldn't get the cable that controls the heater valve to move. Is that the cable you are talking about? Do you know what the "button dance" is for the self diagnostic tests?

 
Rep Power: 518

Yes. Follow it inside to where it is connected to the temp actuator and linkages.

If you can't find it on a google search.......
A library would be a good place to start looking for service info. Many have access to Alldata or Mitchell info systems these days.

 
Rep Power: 0

The cable goes into the firewall. Would I have to take the dash out to get to the temp actuator?

 
Rep Power: 518

No.
It is on the bottom of the heater case, between the heater case and the hump on the floor.

Get a shop manual if you need to. Seriously.



#13 is the temp actuator.

 
Rep Power: 0

That's what I was calling the heater valve. When I flushed the heater core I sprayed water through it and it came out the other tube, so it must be open. I will take it off tomorrow and make sure though.

 
Rep Power: 518

FYI: Today I looked at an 03 Acura MDX (same as a Honda pilot) with the water valve bad, the arm that the cable attached to wasn't really connected to the valve anymore, the shaft inside it had rotted the plastic apart. The cable and the arm all moved, but it really wasn't operating the valve.

Different problem, same result: No heat.


If your water valve had water flow through it, that means it is open and the core should be getting hot antifreeze flow properly. Your problem should be that the (air mix) door inside the heater housing isn't being moved from "cool" to the "hot" position by the servo (actuator).

HTH