Search is not being my friend today. Have a 1993 full size K series 2 door Blazer Sport driving me nuts. The bottom of the screen has the Cold - Hot temperature selection display that is controlled by the temperature selection bar. All of a sudden, instead of showing the position of the normally single temperature arrow, all the arrows flash on and off for several minutes and then quit when you try and change the temperature. Once it quits flashing, there is still no arrow to show whether it's set for cold or hot. I get minor heat after the vehicle warms up so I'm thinking it must be somewhere near the center and all other controls on the panel show up and work fine. Any ideas on what or where to check? I found nothing disconnected, no cut or corroded wires, etc. Baffled and sure the answer is here on the forum somewhere but my search strings are yielding notta.....

 

I keep finding the the head unit is bad and I found this on another sight. Might be worth a try. "Are your temp arrows flashing is that what you mean display flashing? Two issues one the head unit is messed up others say use pencil eraser clean contacts on back of head unit other issues is the temp mode door motor gets stuck a gear cracks thus gets stuck one of the other mode door motors could be messed up.

 

I am also finding a ton of the head units for sale also. Thats not a good sign either

 

Thank you an sorry for the delay. The email got snagged by the damned spam folder. The temp arrows are flashing if you attempt to select anything on the panel, fan, mode, temp, etc. I'll definitely give those a look see. Even with my daughters employee discount at work, the head unit is still expensive and of course, non-returnable if the tape is broken on the GM factory product box. If I figure out what the heck is causing it, I'll let you know for future reference. Have to get moving on it because Vegas will be a hot mess in a month or so.....

 

Well, the AC worked for the summers so far but no heat and the damn flashing is killing me. I found a brand new AC Delco electronic head unit for only $69 from a guy in Canada still factory boxed. Installed today after removing and damaging that brittle desert heat baked trim on the center section. Same issue!! Plug in and fire up the truck and about 10 to 15 seconds later, the electronic temperature display along the bottom starts flashing all arrows on and off. No luck searching but could this be an indication the heater blend door actuator is toast? That sucker is hidden way up in there and looks like I'll have to remove everything except the rear end and transmission to remove and replace it. Any ideas since I hate to literally disassemble most of the dash and heater box/duct work to get at it.

 

My heater control was blinking, and nothing would fix it. - Until. I took apart the dash, removed the bottom dash and radio unit to gain access. I tested the first two Doorman 604-124 blower motor door actuator and the 604-102 were bad. Located on OEM diagram Page#(F-03091 under locations - A and B. There is a C but it was that tested fine. I ordered them from Napa, and also ordered the Blower motor resistor as the lowest setting did not work for the fan.
I swapped the two door controllers. The Resistor on removal looked warped and overheated. Put it in too. buttoned everything up and Re-connected the batteries. Wallah! Worked.