I recently moved into a 1975 house with aluminum wiring. I will be going through and checking/replacing all receptacles and switches with CO/ALR rated ones as I don't have a budget right now to rewire the house. I am wondering if I should be checking all of the ceiling lights as well as some of them would be very difficult to access. Are lights as big a concern with aluminum connections as receptacles? I am sure some of the lights are newer and would have copper wire connected to the aluminum. Should I be concerned about the type of wire nuts used here?Anything else that I should be checking?
Connections at ceiling lights have far less potential for a problem, but a potential none the less. So, while you are at it, go ahead and check them. The antioxidant compound and al/cu listed wire nuts (marriets) are the correct and proper materials to use. I applaud you for having done your homework. After tightening each connector be sure to pull on each and every wire to ensure they are good and tight. When combining solid and stranded wire, slide the stranded past the solid about an 1/8 before capping. We in the trade use 9 lineman's pliers to twist all wires before capping them. An inexpensive pair (of Lineman's) can be had for under $20. A good pair of wire strippers (with built in screw cutters) can be had for about $15. I mention the screw cutter because there is a good chance that somewhere along the line you will find a location where the stock 7/8-1 screw bottoms out against something before it gets tight. If you force it it will strip out. Not to mention it might dig into the insulation on a wire resulting in a short. Screws in devices (receptacles, switches, dimmers etc.) are 6-32 and light fixtures are typically 8-32. I would also get a non-contact tester. A.k.a. inductive tester. Very handy at times. When you are sure the power is off to a box it might not be. On an occasion another hot will be present. The beep testers will quickly alert you to the presence of another live circuit. A multi-tester will allow you to identify wires should you fail to mark them before working on them. If you mark the location of each wire to a 3 or 4-way switch before replacing it you will save yourself a lot of time. Same with wires to any GFI receptacles. Swapping wires location to location may not be correct. Some have the Line terminals on one side, while most have them on the top. But I get the impression you have a bit of experience or a friend who does helping you with this.
There's no problem with aluminum wiring that would require you to rewire your house as long as the proper wire gauge was used. You should replace all of the receptacles and switches with ones rated CO/AL. For lighting, replace the wirenuts with ones rated CO/AL and you'll be fine. From what I remember, Aluminum has a higher resistance than copper so it requires 1 size larger conductors. Aluminum also oxidizes faster than copper. If you have aluminum wires in your panel you should turn the main service disconnect off and put some de-oxidizer (you can find it at home improvement stores in the electrical section) where the wire lug is. This oxidation can make a bad connection causing you to lose voltage as the resistance goes up raising the amperage. This will generate more heat. Aluminum also... well its hard to explain... A/C current cycles its power in a sin wave, it causes the wire to vibrate. You will have to tighten all of the lugs on your electric panel periodically. The CO/AL wirenuts and receptacles/switches help prevent the vibration from loosening the connections causing a short and possibly a shock hazard or even a fire.
