2002 Ford Focus Electrical Problem



I have a 2002 Ford Focus 5door (hatchback) with a little over 90,000 miles on it. Recently the car has been shaking and losing power when going up hills (at the same time the speedometer starts spiking up and down like crazy). Also, about 15 seconds after the car is turned on the speedometer will spike even if the car is not moving. I took it to an ASE certified Master Tech. who originally thought it was the alternator. That has been replaced, as has the power steering pump, speed sensor, air filter. He also ruled out the fuel pump and any pulley driven accessory. He can’t figure it out and gave up, any ideas?


While it is not likely the cause, I would like to see the grounds checked (the battery ground cable and the grounds for the speed sensor and instrument panel.


I’m sure your guess is better than mine, but this seems like a pretty cheap thing to fix, is that true? (If it is I’m sure that means it’s not it because that would just not fit with my life.


Find a mechanic who knows how to do some electrical troubleshooting. At first blush, it looks like there is an electrical short in the wiring to the speedometer. ////// The engine performance on hills may be down because of a dirty fuel filter, spark plugs and wires. Change 'em.


Well, it already had a full tune-up also. The other part of the quandary is that it is putting out up to 200 volts of A/C current (which I surmise is a bad thing).


A “tune-up” doesnt mean they changed the fuel filter, air filter, or the spark plugs and wires. You need to have a shop electrician check out the electric system …including the alternator output. There should be no ac in the dc.


The mechanic I went to originally told me to take it to a dealership, would you guys recommend I take it to a dealership or try another hopefully lower cost independent mechanic?


This shouldn’t be a difficult problem to find and any good shop should be able to find the trouble if it continues to happen while they are looking into it. As previously mentioned, the speed sensor may be the cause of this trouble or connection to it. That would be my first shot at this problem at least.


Would the speed sensor cause the problem with the A/C current…


The alternator produces alternating current (otherwise know as: ac). Most alternators have built-in inverters which change the ac to dc. Some have the inverters separately located. If the inverters are defective, ac can enter the dc electric system. AC is bad. DC is good. Locate the source of the ac, and remove it.


I took this car to an auto-electric shop which also could not find the cause of the problem. The guy there said that he thought it might be a ‘gen module’ or a ‘gem module’ or something like that. He wasn’t certain enough to do the work, but doesn’t anybody know if this module might cause such problems?