Q: Heater won't work on 1990 Mercedes-Benz 300SL

Everything worked fine yesterday now nothing is working it will start but auto headlights not working no radio no air conditioner or heater windows won't work and remote lock won't work

It stopped working all the sudden. First I replace my radiator and pump. Which they gave me a radiator for an automatic. I have a stick. By had it installed anyway. My A/C worked great but my heater never got very hot just warm. Then my A/C just stopped working about a 6 months after. Then my blower stopped blowing. I turn the knob to high I hoy air but it only works if I am driving more than 25 mph. I can shut it off so it won't blow at all. And when I turn it off it sounds like a suction cup door is closing. I checked fuse box under steering wheel. I read things to check but I'm a little hesitant since I need a video or help to do it. I am a single female, I can not afford to go to a mechanic. I can barely keep my gas filled. Please some one help me. Where I live the whether has been from 99 up to 110 degrees. It hotter in my explore. Plus it feels like heat is coming out of the floors too.

2003 Hyundai Elantra GT 5 door: I had replaced the original Oxygen sensor cable with a NTK brand ($29.00) Oxygen sensor and the [Engine light] went on after the first road test. 1) Do I wait for the engine light to go off after the computer accepts it -or- 2) Buy an OEM or very higher priced Oxygen Sensor? **I heard the Oxyegn sensor is going to set the engine light on even if it is a Bosch, or good brand.....? **it took alot of work and BPBlaster to get the rusted heated heat cover off screw/bolts. Car runs really well, I don't want to place alot more time & money into it and may keep it another 2 years.