This 2001 Ford Windstar came in with the complaint that the alternator was not charging. Simple enough I charged the battery, checked and changed the faulty alternator assembly. The alternator is easy to change but the belt is a bit difficult and requires two people unless you already have the vehicle up in the air. I noticed that the output post in the old alternator was loose. It also had a burnt, crunchy feel to it. I thought that was a little strange so I decided to pay very close attention to the charging system to see if something may have caused this condition. Sure enough there was another problem. I had charged the battery fully with a battery charger so I should have seen charging numbers like 14.25 volts and about 10 – 15 amps output with all accessories off. Instead the numbers were 13.6 volts and 77 amps. Way too many amps with the battery charged and no accessories turned on. I did some checking and found that both of the engine cooling fans were on at high speed. I double checked to make sure the a/c was turned off and it was. I connected my scan tool to check for data related to the fans. Everything looked okay until I looked at a/c data. The a/c head pressure voltage was at 0.00 volts and the a/c pressure was at 0.00 psi.
I did a quick check to see if the system had pressure in it and it did. The next step was to disconnect the a/c high pressure sensor. It is located on the a/c hoses that are at the lower frame rail as shown below.
I check for five volt reference voltage on the brown/white wire, present.
I jumped the brown/white wire to the tan/light green wire and checked voltage on the scan tool. It was now reading 5 volts. I had also confirmed a good ground signal on the grey/red wire.
Jumper wire shown installed in the harness connector.
I installed a new sensor and reconnected the harness.
The new readings and the fans operate as designed now.
The picture below shows the a/c high side pressure switch. It is also sometimes referred to as a pressure transducer.
That one was fixed but no one was happy about the situation in the end including myself. I was happy that I had found all of the problem and fixed it right but there were too many people involved with different interests. Let me explain the chain of events. See Part2.