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1984 GMC C3500 Weak heat in 1984 GMC Truck

Tiny
WIL454
  • MEMBER
  • 1984 GMC C3500
  • V8
  • 4WD
  • AUTOMATIC
  • 98,777 MILES
I have weak heat in a 84 GMC. I have replaced the heater core and thermostat, the supply hose from the core is hot, the return hose from the core in warm. I adjusted the cable to the air mixing door. After all that it still blows on average 100 degree air. The truck comes up to temp 185 and is stable. If anyone has any ideas let me know
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Monday, December 7th, 2009 AT 6:48 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
What temp thermostat did you install? THe factory one is 195. THerefore, the engine should be running at that or higher. Also, have you tried to flush the heater core?
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Monday, December 7th, 2009 AT 11:09 PM
Tiny
WIL454
  • MEMBER
  • 2 POSTS
New core new stat
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Tuesday, December 8th, 2009 AT 2:20 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Do you remember if it was a 195 degree stat?
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Wednesday, December 16th, 2009 AT 8:45 PM

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