Re:HEATER/ELEC. Problems

Thanks guys for all the advice I'm just wondering how to go about back-flushing the heater core on my 1998 GMC JIMMY. I'm willing to try this to see if the heater core is plugged. What I don't understand is why I'm
getting good blowing heat from the dash vents and then when I turn the knob to winsheild defrost, it blows out cold?
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this
knob
Because when it's set to defrost, the heater has to compete with the A/C. H
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OK, you'll have two heater hoses running thru the firewall to your heater core. Simply remove the hose clamps (these guys are the spring-type, super easy to remove), and use a tapered-end sprayer on your garden hose (you know, the real cheap brass ones). Stick the tapered end in one of the hoses and let er rip! Then, reverse the direction of the flow, spraying water into the other heater core hose.
You likely have ok heat from the vents as the heater isn't competing with the A/C evaporator when in defrost mode.
Doc

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