For no particular reason heat is lost temporarily (this may
be a period of many minutes). External temp shows OK. Flaps
appear to be working OK. Going back through the archives,
suggests Ambient Air Temp Sensor may be the culprit. The air
being blown in is external temp which at this time in Ottawa
is fairly frigid!
Can someone confirm before I head to the dealer for the part.
Thanks in advance.
Tony–
Jag_S6
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Jag_S6 sent Thu 22 Jan 2009:
Tony,
It may be the electric water pump for the heater circuit. As the
pump motor runs all the time the ignition is on, the carbon brushes
wear out after 80 to 100K miles. They wear away completely, and
the ‘‘last gasp’’ is the braided connection wires and springs making
intermittent contact with the motor commutator segments. This is
why you can get heat sometimes and not others.
The pump is below the left-hand firewall padding and you can check
if the pump is running by feeling for a slight vibration at the
motor. You can also check if the the pump is running by measuring
the current with a multimeter (10A range) if you pull fuse number
15 in the larger engine bay fusebox and connect the meter probes
across the fuse socket.
The brushes can be replaced by making new ones cut down from
suitable carbon brushes from model shops or utility suppliers, etc.
(see archives for details), otherwise it’s a new pump - not cheap!
Regards,–
The original message included these comments:
For no particular reason heat is lost temporarily (this may
be a period of many minutes). External temp shows OK. Flaps
appear to be working OK. Going back through the archives,
suggests Ambient Air Temp Sensor may be the culprit. The air
being blown in is external temp which at this time in Ottawa
is fairly frigid!
–
Brian: '99 XJ8 4 litre, West Sussex UK
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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