location of ecu

Hi, ive got electrical issues galore. 1999 windstar 3.8. my tranny doesn't like to go into 2nd occaisionally, its really random, it winds up right through the regular shift rpm then it finally kicks in around 4000 rpm. the od light blinks for a while and as soon as it started its gone, it shifts normally(ive already replaced the trs,vss, tss, had fluid and filter replaced all to no avail. )
The abs light will come on even when sitting still, ive checked all the sensors with a voltmeter and verified brake fluid level and even replaced the cruise control switch. the ac cuts out when there is any extra load on the engine ie slight up grade. the windsheild wipers randomly jump about 1/2 inch. and I can hear the a/c fan buzzing on the radio when tuned to am stations. Im guessing a bad ground or ecu problem of some sort might be casing all of this. does anyone know where the ecu is located in the van??? also any ideas where to start trouble shooting next? thanks

Have you done the preliminary check like sound battery that is holding charge, no blown cells etc, alternator is putting out good voltage, grounds are solid at main attachment points (battery, starter, chassis). Do you have a check engine light on, if so, what codes. I've had problems in the past that were all over the place that stemmed from a bad alternator. Electrical components are voltage sensitive and do wierd things when the voltage is off.

If all of the above are ok then I'd consider the more computer end of things.

FWIW, my :2cents:

Piper

The PCM (which is what I think is what you are calling ECU) is located on the passenger side of the engine compartment.......behind the top of the strut mount......
Hard to see with the wiper cowl in place....but it is mounted into the firewall at the top corner of the firewall.......has a thick wire harness....with a big connector going to it.

I did those checks you asked about, grounds look good, battery was at 12.6v when not running, 14.3v when running slightly higher at the alternator. I turned on the radio, a/c and lights and voltage dropped to 13.5v at the alternator and 13.2v at the battery. should that still be at 14v with all the accesories running? I let it run for 10 mins and it seemed to drop little by little down to 13.2v

That seems a little low to me, though Ford spec at 2000rpm is 13 to 15 volts with NO load, nothing on. Haynes says 14 to 15 volts. You mention interference on the radio with the ac fan on. Does anything else cause that? Will the fan in the other settings like vent, heat do that? Is this something new that came about the same time as your other symptoms? Is it only on AM or both? Irregardless of what causes your interference, just on a hunch, turn on the interference on your radio, then pull the three wire connector off the alternator and see if it goes away. If it goes away, you May have a bad alt. If it doesn't go away, it's probably not caused by the alt, but you should consider replacing the noise supression capacitor(s). Also, see what kind of in the car test results you can get at your parts store on it. Unfortunately, the best method of testing it is pulled out of the van, also at your parts store. As per Ford's service manual, their idea of fixing your problem would be trying a known good alternator and see if that fixes it. I'm not making that up!!

I just replaced my alt 3 months ago due to a host of electrical problems I was getting and my new one puts out 14.4v with some accessories on. I too think your alt is a bit flakey. When was it last replaced/how old is it? With the number of really weird things going on in your van this could be the culprit.

Piper