heat is blowing, But weak

[Nick.koehler6]

The heat in my 83 k10 is blowing but it is very very weak. Even when I put it on high. What could cause this and what could fix this? any help will be greatly appreciated!

 

[350runner]

Low coolant and a clogged core. Check the coolant level and try reverse flushing the core

Sent from the dust in front of you!

 

[89Suburban]

Bad ground on the blower motor. Corroded terminals on the resistor plug. Faulty blower switch. Run a jumper from the Batt + post to the blower + post and see if it blows hard, then troubleshoot from there.

Troubleshooting link:

http://www.gmsquarebody.com/forum/showthread.php?p=246424#post246424