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Climate control craziness!

932 Views 5 Replies 4 Participants Last post by  Opus
Hello all, my '89 420 SEL is giving me climate fits!

In summer, AC works, but system switches from AC to heat and back to AC.
AC comes back on just before heat becomes uncomfortable.

In colder weather, heat comes on but AC cycles on and off as well.
Noticed that even when heat is on the vent that blows into the back seat blows cool air.

Exchanged climate control unit with no improvement.

Any ideas? I'm at a loss on this one....

Thanks in advance.
1 - 1 of 6 Posts
Try replacing the monovalve... it's located between the firewalls near the battery. You can either work fast to avoid much coolant seeping out while you change it, or drain some coolant out so you can work slower. This is usually the problem when you get this cycling effect.


PS: My location info is based on a LHD Series 2 car!
1 - 1 of 6 Posts
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