Looking for some help. My blower on the heater works on high but not on MAX. Any help will be appreciated.
First place to check is the resistor bank wired in-line with the fan motor. Different resistor loads are applied to the circuit at the different speed settings. Believe it's on the plenum accessed from the engine bay.
"High" and "Max" should be the same blower setting. "Max" involves the air recirculation, not the fan speed. I'd be looking at the control head. Of course, a REAL service manual would be helpful.
No, on the 70-72 climate control, Hi and Max are different. Recirculate mode is the other switch on the same panel. The problem is the high speed relay on the firewall. You can see the relay in this engine picture. It's mounted with 2 bolts on the firewall right behind the air cleaner, between the vacuum reservoir and wiper motor. Rockauto has them, https://www.rockauto.com/en/catalog...trical-switch+&+relay,blower+motor+relay,3088 https://www.rockauto.com/en/moreinfo.php?pk=532141&cc=1379763&jsn=410&jsn=410
Yup. High speed relay, or the wire harness associated with it. Seems to me, GM had some problems with the harness overheating when the blower motor bearings got stiff (or other motor fault.) Blower motor draws excess current, wire harness or the relay contacts burn up. Maybe there's a fuse that pops. DON'T replace the relay without inspecting the wire harness, the fuse, (if there is one) and also testing the blower motor for current draw.
