[apex]

brrr... 19 degrees last night!



Which reminds me to ask about my heater which seems to run cold unless I rev up to oh... 2000 rpm at which time the heat - usually - comes on.



The heater has been intermittently operational this fall - wouldn't heat up even at speed - but sometimes all of a sudden would spring to life - then go cold again - but now this behavior of "cold until revved" seems fairly predictable.



Any thoughts? Contrary to what I just indicated, while troubleshooting this I was able to watch the heater control valve operate as expected while at idle and moving the temp valve back and forth.



Of all the dianostic choices (solenoid, tem gauge, heater control valve) could these symptoms indicate a weak or failing vacuum system?

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[Mike in NJ]

[quote name='apex' post='30219' date='Jan 26 2007, 11:08 AM']brrr... 19 degrees last night!



Which reminds me to ask about my heater which seems to run cold unless I rev up to oh... 2000 rpm at which time the heat - usually - comes on.



The heater has been intermittently operational this fall - wouldn't heat up even at speed - but sometimes all of a sudden would spring to life - then go cold again - but now this behavior of "cold until revved" seems fairly predictable.



Any thoughts? Contrary to what I just indicated, while troubleshooting this I was able to watch the heater control valve operate as expected while at idle and moving the temp valve back and forth.



Of all the dianostic choices (solenoid, tem gauge, heater control valve) could these symptoms indicate a weak or failing vacuum system?[/quote]

If you see the valve moving, then vacuum is probably fine. It might not hurt to bleed the cooling system.

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[apex]

Thanks, mike. It's interesting - and I checked this last night - how fast the heater cools down at idle, and how fast the heat comes on again with rpms around 2000.

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