Mrs. R has been complaining that the headlamps on her 1989 Toyoto Corolla are too darn dim, and for a fact, they aren’t the greatest headlamps I’ve ever seen. So last night, while the Littlest R was in ballet class, I wandered across the street to the import-auto-ricer-trinkets store and purchased a set of 65/100W Nokya bright bulbs for her car.
So I bring them home, expecting to be met with glad cries of joy, and Mrs. R asks, “Are they okay to put on my car? I don’t want to burn up the wiring.”
Okay, I’m an engineer, I can figure this out. 100 Watts at 13.5 volts would be 7.4 amps. Each headlight on the Toyota has its own 10-amp fuse. So it looks good. Surely Toyota would design the system so that the fuse blew before the wiring burnt up, right?
Mrs. R, stubborn woman that she is, is not satisfied. “I don’t want to be stranded with blown headlight fuses. You read all those newsgroups, don’t you? Why don’t you post a question?” (Note the implicit lack of credibility that all us long-term husbands have to suffer under. It’s the legacy of that one time that you accidentally installed an alternator backwards and drained her battery, back in 1984)(I personally feel that the alternator was defective)
Okay, so here’s a pair of questions:
Is my thinking right vis-av-vis fuse sizing; that is, the fuse blows before the wiring does? Have I missed something?
Does anyone have experience with installing brighter bulbs on a 1989 Toyota Corolla? Any ill effects?
I have installed higher wattage bulbs (H4’s) in my Subaru Legacy with good success. Brighter than the factory installs and no problems. There are several type of bulbs available. Brighter (higher wattage)low beams, brighter high beams, and brighter both beams. I decided to go with brighter both.
However on my 97 Ford SUV it was a different story. The factory was, IIRC, 55/65 watt. I installed 80/100s and melted the plastic connector that connected to the bulb! Actually it melted a connector that had been installed by the dealer after the factory connector had developed an intermitant connection. The factory connector on the other lamp did not exhibit any problems.
There are bulbs that are brighter due to new technology rather than higher wattage. If you have doubts about the electrical system, they might be more suitable. Check with J. C. Whitney, they have lots of bulbs in their catalog.
The bulb’s wattage rating might be calculated at 12V. My experience is that the only reliable way to know the actual amperage is to measure it (ammeter).
Fuses are certainly meant to blow before wiring burns up. Fuse ratings tend to range from 25%-100% above expected constant usage, which leaves some breathing room for amperage peaks that often occur when a device is first switched on.
Operating a circuit at a higher amperage than before can sometimes overstress wiring, switches, and connectors. This is usually not a dramatic, sudden effect, but rather one which shows up over a period of time.
My suggestion is to measure the actual circuit amperages with both the old and the new bulbs. I think that will give you the info you need with more certainty than any theoretical calculations.