why does my temp guage flucuate and heater only work when reving around 3 k rpms

1994 MAZDA B4000
84,000 MILES
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TNORTH3
  • MEMBER
  • 1 POST
Replaced thermostat temp sending unit and flushed coolant system. The truck reads hot when driving and heater blows cold but when u rev it to 3k rpms it drops to normal operating temp and the heater starts to blow warm again
Jan 6, 2012 at 1:37 PM
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SATURNTECH9
  • ✓Experienced Mechanic
  • 30,869 POSTS
Sounds like the heater core is restricted i would check athat first.Unless you are low on coolant or have air in the cooling system?
Jan 6, 2012 at 2:37 PM
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