300 SDL intermittent heat

The heat in my 86 300 SDL works intermittently. The blower motor seems to be ok, although the speed fluctuates, but it mostly just blows in cool air when the heat is turned on. Anyone know
what might cause this? Thanks,
-- Jeff
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Easy one. Replace the heater water monovalve diaghragm, behind the battery on the firewall.
Bill Ditmire Ditmire Motorworks,Inc. 425 White Horse Pike Absecon,NJ 08201 http://www.ditmire.com 609-641-3392
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