-
Contributor
22 Answers
- Posted on Dec 04, 2010
Re: 89 740 volvo GL heater failure
Several suggestions:
- Your thermostat needs
replacement and your dash gauge is not reading correctly. Cheap and
easy to put in a new thermostat to confirm.
- Your
heater core has a deposit of sediment or minerals restricting the flow
of warm coolant in which case the system may benefit from a backflush.
- The heater water valve has a blockage restricting flow and may be in need of replacement;
- You have a vacuum leak which causes the heat vent control to work improperly;
- Your
firewall-side heater water valve was installed backwards; The arrow on
the valve points to towards the firewall inlet, not back towards the
engine.
- Control cables from the heater control unit
to air mixing doors are maladjusted or broken. In heater-only cars (no
AC unit), the water valve (which is inside the cabin, above the left
footwell) is controlled by a cable from the air mixing door.
-
Check the heater hoses, I have seen several 700's where
they are swapped over and it results in ZERO heat. See the section on Water Valve Replacement for correct installation instructions.
×