3800 with 172k has begun to lose heater temp. I still have heat, but greatly reduced. Changed out thermostat and topped off anti-freeze, but got no improvement. I'm thinking a back-flush may be in order in an attempt to clear junk in core. If that doesn't do it, how big a deal is it to replace the heater core? Is there anything else that should be checked first? Temp control? How?Thanks.
With that many miles it is possible the heater core is clogged. Back
flushing may help, but don't get your hopes up. The passages are
pretty small in them. Unlike the cars of yesteryear, it is difficult
to get most cores out to replace them.
It is also possible the damper is not closing properly. On mine
(2001), one side was hot, the other cold depending of whether you were
running heat or AC. I'm not sure how to check it as I gave the car
away before it became a problem. Engine still ran well, everything
else was going to crap though so it was good riddance and my last ever
reduced. Changed out thermostat and topped off anti-freeze, but got no
improvement. I'm thinking a back-flush may be in order in an attempt to clear
junk in core. If that doesn't do it, how big a deal is it to replace the heater
core? Is there anything else that should be checked first? Temp control?
Most likely a mixer door malfunction. Could be as simple as the clip
connecting the cable to the door broke. Does the A/C blow cold?
I concur that it's more likely a door issue, particularly if it
was sudden onset. Another approach could be to monitor
the temperature of the heater core inlet and outlet hoses
upon cold startup, with the temperature control set to its
hottest position, fan off. If at a fast idle they seem to warm
at the same rate, quickly attain the same temperature as
one another and then other coolant hoses upon the opening
of the thermostat (determinable by the dash temperature
gauge or more precisely the upper radiator hose), then
flow through the core, and an even less likely case of
clogged exterior fins, is probably not the problem.
I had a 2004 Century 3100 with the dual temp controls, and the
passenger side would blow hot all the time no matter what you set the
control at for that side. Unacceptable in the summertime.
I posted somewhere and got this reply, and it worked:
"This can be caused by either a intermittant feedback error in the
itself, an overflexing door or a fault in the control head.
You can attempt a reset procedure.
Use the following steps to perform the calibration update:
1. Turn OFF the ignition.
2. Remove the battery positive voltage circuit fuse of the HVAC
Important: The module memory will not clear if the battery positive
circuit fuse is installed in less than 60 seconds.
3. Wait 60 seconds.
4. Install the fuse.
The fuse in the in I/P fuse panel and is labeled HVAC. This will sweep
and mode doors in an attempt to relearn the positions. Bear in mind if
a fault in the actuator, controller or related wiring and it cannot
door position it may re-occur."
This solution did work, and eventually the original condition
re-occured. Then I performed the above procedure a second time, and
haven't had a problem in several years.
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