Hi everyone,

I'm having two problems with my 2002 Focus w/ an auto transmission. One is that during acceleration, seemingly in any gear, the transmission will "skip" and downshift for a couple seconds, then "knock" back into the appropriate gear. This leads me to believe there is an issue with the transmission, so I made an appointment with a tranny shop to scan the thing and make sure all codes are correct. The second issue is that the headlights and radio have begun flickering and dimming. This makes me think the alternator is at fault. Often, but not always, these two issues will happen at the same time; the transmission downshifts and the radio & headlights flicker, then they correct themselves almost immediately.

I'll add that 10 months ago I had a new radio installed; no amp or anything, just a head unit. Other than that this vehicle has had no major issues or repairs in its 12-year, 85,000 kilometer lifespan.

Is the alternator and transmission linked in some way? Could this be a battery issue? Fuses? Or two separate issues altogether? Are these issues a cause for concern?

I'd appreciate the insight that any of you have into the innerworkings of this vehicle, whether you've experienced similar issues or simply know more about it than I do and are willing to share.

Thanks in advance,

Alex

It could well be related as a bad power flow would affect how gearbox manages itself

In pretty much the wrong order:

The second issue is that the headlights and radio have begun flickering and dimming. This makes me think the alternator is at fault. Often, but not always, these two issues will happen at the same time; the transmission downshifts and the radio & headlights flicker, then they correct themselves almost immediately.

I'll add that 10 months ago I had a new radio installed; no amp or anything, just a head unit. Other than that this vehicle has had no major issues or repairs in its 12-year, 85,000 kilometer lifespan.

Is the alternator and transmission linked in some way? Could this be a battery issue? Fuses? Or two separate issues altogether? Are these issues a cause for concern?

In a number of Ford vehicles -Cougar, Mondy Mk III, and probably others - there is an issue whereby the lights flicker at high-ish loads and when the alternator isn't charging very hard (low-ish engine rpm).

Now, this probably sounds expensive, and it can be if you get a Ford dealer to fix it (my experience suggests that even though there is a TSB about the fault, dealers will do anything to stop you getting a fix for free - given that it is a known fault, you'd think that they take a different approach...or, maybe, not).

In any case for applicable cars, there is a 'harness' (a single piece of wire with a ring terminal at one end and a bit of extra insulation) which costs about £30 if you buy it from Ford. The fitting (probably an hour's real work, most of which will be spent scratching your head and mumbling 'how do I keep this out of the way of that hot bit?) will be £100+ at a Ford dealer, and given that they should just be following some simple instructions, you'd have to think that they have a cheek.

Anyway, I'm sure a search will turn up some kind of guide. You just need to add an extra bit of wire to reduce the voltage drop. The ford kit just modifies the +ve battery supply, but I'd be tempted to also add an extra piece of heavy wire between the engine, near the alternator and the vehicle ground near the battery.

Is the alternator and transmission linked in some way? Could this be a battery issue? Fuses? Or two separate issues altogether? Are these issues a cause for concern?

Well, if the voltage does dip down below what is required for the control module to work, then it could easily be. I don't know that it is, but it could be. In this case, the module probably has to drive a high current solenoid or two at the same time, which makes the problem worse.

Thanks for the replies. What you've both said is in line with what the guy at the tranny shop had to say as well. Though he wasn't able to reproduce the symptoms in person (don't you love how a vehicle won't act up for the mechanic but will as soon as it leaves their shop?) he suspected some kind of miscommunication between engine components with the power being the main suspect. No problems or codes were found with the transmission, thankfully. Will continue to investigate and will post back if/when the issue is resolved. Thanks again for the info.

Bare in mind that it could easily be something as simple as a corroded connector and either removing and inserting the connector a few times or applying some contact cleaner could make the problem go away. it is far from guaranteed that this is the cure/temporary fix, but it might be and is easy to do...once you know where the problem is (...assuming, etc, etc).

On some cars you do hear of this kind of problem when a ground connection, shared by several modules, starts to disintegrate.

Apparently the problem is getting worse. I'm having the battery & alternator tested tomorrow.

Looking at this again, I wonder whether you are getting a spurious 'kickdown' signal. It would certainly be worth checking around the accelerator pedal, to see if there are any wiring issues there.

Or perhaps a dirty fuel filter. Battery & alternator checked out fine. Have a Friday appointment for a "deep diagnostic". I don't have a jack to get in and replace the fuel filter, but perhaps the diagnostic will pinpoint the cause. It actually costs $$, whereas everything else has been free tests, so hopefully it will get to the bottom of this. At least I've ruled out the tranny, the battery, the alternator, and the type of fuel.

Fuel filter swapped out and the problem has gone away so far. The filter was due for replacing and in the last 24 hours (and about 50 miles of driving) there have been no power sags.

Glad it's resolved normally that would be one of my first comments but I looked a bit too deep lol. Fingers crossed it stays fixed!