Troubleshooting after replacing my heater core
 

So my 2000 Blazer project is almost done and ready to be sold. There are just two little quirks that I noticed once I got everything put back together after replacing the heater core. I'm not sure if it had these problems before I tore it all apart or if it was because I didn't put everything back together quite right.

The first problem is with the climate control. Everything works mostly right, but if you have it so that it's blowing on your face and then switch it to defrost, it wants to keep blowing on your face. However, if you switch it to cold and back to hot again, it will move to the defrost like you want it. I'm guessing it's a vacuum leak somewhere, but I don't know which connections I should check and was wondering if someone could point me in the right direction.

The second problem is with the speakers. The front speakers work fine, but I noticed that the rear speakers are not working. What connection(s) should I check? I also noticed that some of the lights on the head unit don't come on, like some of the ones that backlight the numbers for the radio presets. I'm not sure if that's related or not.

These are both pretty minor quirks in an otherwise good truck; if diagnosing and/or repairing either of these two issues is going to be too difficult or too expensive, I'll probably just leave them.

Thanks in advance for the help!

For the HVAC: On the left end of the heater case, above the gas pedal, there are two vacuum actuators:

Attachment 31453


The lower actuator has two vacuum lines and is a two position actuator. Check vacuum on each line and operation of both actuators when you move the mode switch to different positions. Another possibility: When you split the case to do the heater core, one of the doors may be binding up, doesn't take much.


Radio speakers: OEM speakers are pretty cheesy, they may have taken a dump. There are 10 bulbs behind the radio faceplate. The radio must be removed and disassembled. Each bulb must be de-soldered and new bulbs soldered onto the printed circuit board. Ebay has the bulbs, cheap. Use a low wattage soldering pencil and a desoldering tool. 60/40, lead/tin, rosin core solder. Not difficult, but time consuming.

Excellent. Thank you. I'll check those actuators when I get home from work. I think I'll just ignore the radio, though, since I'm just selling it and it's really not that big of a deal. The front speakers work fine and all the buttons work; they just don't all light up.

I don't want to hijack this thread but after changing my heater core in my 98 sonoma highrider the airbag light came on & stayed on. Was not on before install. Is there anyway to get it out, or will have to go to the dealership?

schrack, there is probably a connector that didn't get connected back up when you did the core. A GM dealer can scan the SRS and retrieve the DTC and figure out what the problem is.

Me & my brother in law have tripled checked all wires are hooked up like before. Have been researching on different forums & alot of people say after changing heater core the airbag light stays on. Was wondering if there is anyway to reset it?

Each time you turn the ignition off, it resets. The SRS, (Supplemental Restraint System) module runs a self test each time the ignition is turned on. If it fails, the light stays on, and a DTC is set in memory. You'll need to have it scanned with a scan tool capable of accessing the SRS module.

@ Hook: Both actuators seem to be working fine and I did not notice any leaks. Maybe they're just a bit stiff with age. I also figured out that, if you turn the fan down to 1, it will be a little less stubborn. I think I'll leave it as it is.

@ Schrack: If you take it to AutoZone, they'll run a scan and clear the code for you for free.

Schrack, AZ can't do it, they can only check powertrain, and maybe ABS. No SRS, no BCM, no IPC, no HVAC, no 4WD. Gotta have a high end scan tool to access that stuff and their $500 cheapies won't do it.

Oh, sorry. My bad. I didn't realize it was that much more complicated than the check engine light.