Having ac/heater problems

I have a 99 alero and my heater and a/c comes on and off when it wants to. Then when it decides to come on it only works on the two highest settings. My fiance replaced the blower motor and the resistor and I am still having this problem. Any suggestions!?

I have a 99 alero and my heater and a/c comes on and off when it wants to. Then when it decides to come on it only works on the two highest settings. My fiance replaced the blower motor and the resistor and I am still having this problem. Any suggestions!?

In a worse case scenario you may have an ignition switch assembly acting up. The contacts carbon up over a period of time. Plus the HVAC control units have been known to go bad in Aleros. Although access is difficult it could be troubleshot. On the blower motor resistor did you get an aftermarket or GM OEM replacement?

It is aftermarket. I thought maybe it was electrical related since it shuts off sometimes

How do I narrow it down? What should I check first

How do I narrow it down? What should I check first

The aftermarkets like the Wells brand from Autozone have a high failure rate. It is recommended to use an OEM AC Delco so you still have a possibility of the replacement blower motor resistor being bad. Troubleshooting the HVAC head unit is very difficult short of just changing it out but it may not be the cause. Plus it will cost the most. You could remove the HVAC control unit just to see if it is not a looose electrical connection. Since positions 4 & 5 work you can rule out the blower motor. The BMR is still the cheapest part to replace. So it looks like it is 50/50 between the BMR and head unit.

On the ignition switch normally you'll get other symptoms like cruise control not working or headlights acting up in addition to blower problems. Good luck and let us know how it turns out.

Thanks soooo much I appreciate it and will let you know what happens!

I had the same problem try wiggling the connection thats wat i did and it works fine now lol

I use to just be able to kick it and it would come on but now that doesn't work. It is working at the moment but it seems to have a mind of it's own. I think I'm just going to take it to the shop because messing with all those wires is to risky. Thanks though!

I have a 2001 GLS with the blower motor resistor problem. The AC Delco replacement has the nuts located on the opposite corners of the original. Will it work? Or should I go to a dealer and get the GM part? Also having a problem getting the nut that's against the firewall out. It's in a little well area only a few inches deep. Flexible ratchet doesn't work as the adapter and socket are too long to fit in this small space. Any suggestions?