The ohms are not that big of a deal. 8 ohms is the most common for home audio systems but 3.2, 4, and 6 ohms have also been used in cars. The resistance values are more for the proper operation of the amp inside the radio but you have to consider that the wires going to the speakers are going to have some resistance too. If you measure from the speaker plugs in the radio with an ohm meter, you'll typically find between 10 and 20 ohms for the total circuit. What's important, if you want to be that critical, is to look at the speaker resistance specified for your new radio. Very likely it will be listed as "4 TO 8 ohms", or something like that.
To add to the misery, every manufacturer uses speaker shapes and sizes that they are sure are better than anything anyone else has ever come up with before. Some have three mounting screw holes instead of four, and you will never find any aftermarket speaker that is a direct fit. I have a boxful of new GM speaker adapters that allow standard speakers to be used. You will find similar products at Best Buy.
If this is a normal amp like GM and Ford use, there will be a wire on your new radio to turn it on when the ignition switch and radio are turned on. It may be labeled "power antenna" but it does the same function. When GM and Ford use amps, they must be used with the matching radio for proper volume and clear sound. When Chrysler uses amps, they only change the tone for the shape of the vehicle. They never increase volume or power so any radio will work with any system.
If you have an amp designed to irritate other drivers, they have their own turn-on circuitry and use a fat gauge power wire connected directly to battery power. You might consider running it under the car instead of under the carpet where it can get crushed by the rear seat brackets, and popping into the rear through one of the rubber plugs in the floor. Be aware that starting with the '87 models, GM went from one of the best generators to by far the worst pile ever developed. Due to the design of their internal voltage regulator these generators develop huge voltage spikes that interfere with the many computers and their sensor signals, and they can damage that regulator and the internal diodes. It is very common to go through four to six generators in the life of the vehicle, and the load placed on the electrical system by obnoxiously huge amplifiers will cause that regulator to drive the generator harder to try to keep up with demand. That will add to the voltage spike problem. The one thing that will reduce the number of repeat generator failures is to have a fairly new battery installed. As batteries age, they will still crank the engine just fine, but they lose their ability to dampen and absorb those spikes. Batteries in GM vehicles seem to start allowing problems to develop when they get to be about three years old. The old battery will still work fine in an '86 or older vehicle with the better generator design.
If you do have to connect a large cable to battery power, never stuff it under the terminals on the battery. Those side post terminals have caused GM owners so much grief for many years that now Chrysler wants to get in on the action too on some of their cars. The surface area for the cable's electrical connection is very small and just barely good enough to pass the required very high current for the starter. Sticking anything between the battery and cable will degrade that electrical connection. That will REALLY let those voltage spikes cause all kinds of problems. Instead, look for a smaller positive cable that attaches with a bolt and nut to the under-hood fuse box. That is a better place to attach extra cables, but the existing cables and the stud should be cleaned up with sandpaper first to be sure they're shiny. Those connections cause a lot of intermittent problems on all brands of cars so be sure the nuts are tight.
I just acquired a big pile of GM wiring diagram books last week. I'll look through them to see if I can help with the power outlet problem. I never looked to see if they're on the same circuit as the lighter.
Tuesday, December 20th, 2011 AT 5:15 AM