This 1998 Ford Windstar with the 3.8 liter engine came in with the complaint that the alternator would not charge. The alternator had been replaced twice and still nothing. Imagine that? I confirmed that the alternator was not charging and then moved onto circuit tests.
The main battery lead at the alternator must have battery power at all times.
The green wire with a red stripe should have less that battery voltage but at least a nominal five volts with the ignition on. Using a test light the bulb will glow but not be as bright as if it would when the light is touched to full battery positive.
There should be full battery voltage on the yellow wire at the regulator harness connector. There was no voltage present so logic dictates that this is why the alternator does not work. Two to three minutes of diagnosis and I knew why the alternator was not working. Now I have to figure out where the problem is.
Using Mitchell On Demand I viewed the wiring schematics and found that the yellow wire is supplied battery voltage through fusible link “C” located at the rear of the underhood fuse box. To access the rear of the fuse box and locate the fusible link the MAF sensor and intake tube had to be removed.
A few clamps and a lot of twisting and wiggling of components and the parts were out of the way. In the following picture I am pointing out the brake pressure switch. I am doing this to draw attention to the fact that this is the original design that was recalled due to a fire hazard. The newer design uses a different switch and subharnesses in between the original connector and the replacement switch. I noted the need for the customer to call the local dealership about this recall.
There are two clips that have to be released while the fuse box is being lifted slightly. You may be able to skip this part. I did it for more access to the wiring for testing and taking pictures.
I located the fusible link that was attached to the same yellow wire that is located at the regulator connector and it was good as evidenced by the illuminated test light that is probing the yellow wire just past the actual fusible link. So I have an open circuit somewhere between here and the alternator.
Looking around I spotted the engine harness to main harness junction block just behind the throttle body area. There is a bolt with a 10 mm head that secures the two halves together.
After loosening the screw and tugging on the connectors the two halves came apart. I could see the problem once the connectors were separated but I had to maneuver the connector up and around through the throttle cable area to be able to work on the repair.
I used a long screwdriver to release the latch that was securing the lower connector to a metal bracket. It is just like the ones used to secure the fuse box.
I then had to maneuver that connector and wiring up between the master cylinder and the throttle body cable bracket to have enough room to work with it.
I chose to make a two wire quick disconnect harness up to make the bypass of the burnt terminals. Also note that I used a sealer on the cut ends of the wires in the original connectors. This will prevent fluids from entering into that connector through the open wire ends.
My male and female two wire connectors wired into both halves of the harnesses.
After putting the main harness connectors back into their original locations, I connected my installed bypass connectors.
I secured them with a wire tie to the original connector bodies.
A quick check and the regulator harness connector and power is now present on the yellow wire.
I started the engine and the alternator was now charging.
In the 1999 and later year models, Ford Motor Company redesigned how the alternators are controlled and the above tests are not relevant. The tests do apply to 1996, 1997 and 1998 year models with the 3.8 liter engines. The Windstars with the 3.0 liter engine have a similar alternator and tests but there is one extra wire that this one does not have. It is a white wire with a black stripe that connects between the center harness connector terminal and a single lead that plugs into the side of the alternator. One has to check to make sure that there is continuity between both ends of the white/black wire and confirm that the harnesses are connected to the alternator.