Wednesday, August 27, 2014
Help! Vehicle electrical problems
I could really use some diagnostic help in determining what's going on with my 2005 Ford F-150 XL truck. I've got three intermittent problems that I think are all related.
1. For several months now, the cruise control will occasionally cut out in the middle of a drive with no warning. It won't allow me to switch it back on, either. Sometimes this is accompanied by a sort of crackling sound from the steering column, as if there were an electrical short-circuit, but sometimes not. There's no smell of burning or any other electrical problem. If I stop the car, turn off the engine, wait a few seconds, and turn it on again, everything works as normal. The fault is intermittent: nothing might happen for several trips, then for two or three in a row it will reveal itself, then it'll go away again for a while.
2. For about six to seven weeks, I've had an intermittent problem with the air-conditioning. While driving, it'll suddenly shut down completely - compressor and fan together. If I do nothing, after one to two minutes it'll come back on again. If I thump the dash just next to or below the fan switch, it'll usually come on again at once. Like (1), the problem comes and goes.
3. Over the past week, on three separate occasions when I've switched off the truck, the brake lights have continued to burn. On two occasions I only noticed them when I came back to the truck; on the third, I was looking for the problem, and noticed it at once. If I restart the truck, wait a moment, then switch it off again, the brake lights go out again as usual.
I'm convinced these problems must somehow be related. A dealer agrees that (1) and (3) are probably related, because (their service staff say) the brakes has to disconnect the cruise control when they're applied; so if a single switch in that circuit is faulty, it might be the cause of both problems. However, they can't see how (2) is related to the other issues. What's more, they claim they can't diagnose the problem unless the faults occur while they're driving the vehicle; and given that they're intermittent problems, there's no guarantee they can reproduce any or all of them. They're willing to try, but I'll have to cover labor costs, so I might end up paying several hundred dollars without finding a fix at all.
I've had suggestions from a couple of mechanics that since the truck's now a decade old, it might be a good idea to retire it and buy a replacement; but have you seen the price of trucks these days? It's ridiculous! I've thought of buying a used truck as a replacement, but I've only driven 60,000 miles in mine, and all the used trucks I've seen in the 5-6 year old bracket will cost me mine as a trade-in plus at least $10,000 in cash for a vehicle that's already covered many more miles than mine has. I could look at replacing it with a fuel-efficient small vehicle to run errands around town, reserving the truck for longer trips or hauling things; but then we'd have a third vehicle to look after, insure, etc. - all additional expenses, and on our limited budget, I'd rather not incur them. One mechanic has suggested replacing the entire wiring harness in the cab, on the principle that it's probably going to solve the problem even if we can't identify what the problem is! It'll cost a lot (probably into four figures), but in the absence of certainty over specific circuits, he reckons it's the most likely 'cure' for what ails the truck.
Frankly, I'm at a loss what to do next. I don't want to drop several hundred dollars on a dealer investigation that might not find the problem; but I can't carry on driving a truck that might develop worse problems over time, and strand me at the side of the road. I also really don't want to spend a couple of thousand on a complete wiring harness replacement in the cab. Can anyone offer helpful (and practical!) alternatives? I'll be very grateful.
Thanks in advance.