560 SL 1989

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John 560SL - 26 Dec 2006 14:42 GMT

Heater does not come on. Blower works fine, (only cool air). If I
turn off the engine and restart it, I get heat for about 1 minute.
Position of tempurature wheel makes no difference. Turning it all the
way up does not cause heat to come on. Any ideas? Bad sensor
somewhere?

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Tiger - 26 Dec 2006 15:03 GMT

More likely bad heater selenoid valve that controls the flow of hot coolant
to heater core.

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Karl - 26 Dec 2006 15:03 GMT

Replace the mono valve insert. In the heater water valve on the firewall, passenger side.

> Heater does not come on. Blower works fine, (only cool air). If I
> turn off the engine and restart it, I get heat for about 1 minute.
> Position of tempurature wheel makes no difference. Turning it all the
> way up does not cause heat to come on. Any ideas? Bad sensor
> somewhere?

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John 560SL - 05 Jan 2007 18:10 GMT

Yes, it was the mono valve. I did not see any tears or wear in the old
one. It looked brand new. Replaced it anyhow. Nice and warm now.
Funny thing, the metal sleeve that you put back in last (after the
washers) had some notches cut out of the top edge like it was supposed
to mate with something. I saw nothing that seemed to line up with the
notches, but it is not leaking so I guess that is not important?
John

> Replace the mono valve insert. In the heater water valve on the firewall, passenger side.
>
[quoted text clipped - 3 lines]
> > way up does not cause heat to come on. Any ideas? Bad sensor
> > somewhere?

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