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Charging Problem 1989 dodge caravan, 191,000 miles ...

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Question by Sad Joe
Submitted on 9/19/2006
Related FAQ: rec.autos.vw [W] GENERAL, FREQUENTLY ASKED QUESTION (FAQ)
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Charging Problem 1989 dodge caravan, 191,000 miles

Notes:

Original problem occurred after replacement head installed, prior to that, no problems, however I assume, nor claim, nor indicate anything triggered the alternator problem during head change just noting this for time reference.

As mentioned, immediately experienced the problem of charge loss, on and off after the head change, I did extensive trouble shooting, replaced alternator, and the ECU which contains the voltage regulator, this didnít solve anything. I cleaned all the harness plug ins, used contact cleaner, wire brush where I could, and used WD 40 followed up by grease on the connectors, cleaned, and I mean really cleaned, all relay contacts on fender relays, and also all connectors going to the bank of relays on the left hand fender. That didnít fix anything.  Shortly there after the alternator started working on its own, alternator charged fine for about 3000 miles then problem reappeared. I could kick start the charging process by pushing in the A/C switch then immediately pushing the off switch, when pushing the off switch, then the alternator started to charge again, some times it kept charging some times it died out after a few seconds. This is consistent with the first time I noticed the problem, what happened there was, I went to turn on the AC and the alternator stopped working, but when I turned off the AC then it started charging. I tried using the headlight switch as a test, that didnít re start the charging process; I tired using the high fan position that didnít re start the charging process either, only the AC on off switch.

I checked continuity of field coil wire from alternator to ECU . It checked good at the time I checked them anyway.

Often the alternator would start charging after the A/C button was pushed and released. I am thinking the ECU gets a single from the switch and it is not direct to  relays which operate the AC fan and clutch coil.

Symptoms:

Both A/C fan Relay and engine fan relay chatter when charging stops (relays get signals from the ECU) I am sure this is not due to low battery voltage; voltage reads good 12 volts when this happens. I am thinking something inside the ECU is causing the relays to act this way, relays get the signal from the ECU to turn on or off as far as I can tell

The relays chattering, this tells me there is more going on than just a no charge problem , I am thinking there is a problem with signals going to the ECU, I know the ox sensor was changed, I dint check down there for shorted wires, I really cant see how that would cause the rest of it to go nuts but who knows. Something to check.  I know idol speed is fast, wasnít before head change, not saying anything here is related to the head change, but just noting for trouble shooting purposes.

Engine radiator fan runs slow continuously when alternator drops out, Fan relay for the radiator engine fan chatters, (it is turning on and off, along with AC fan relay, AC fan on condenser near grill, does not run when this happens but it will run when AC switch on dash is pushed)  Two relays chatter, I think I am right saying the one is for the AC fan, I have the manual which tells clearly what relays do what but then maybe I am wrong. The engine radiator fan turns on when charging stops, even when engine is cold. Pulling the wire off the engine temp control sensor, near thermostat stops the chatter after a few seconds, and fan stops. RPM increases. The temp sensor runs though the ECU then from there to the fan relay. Doing this does not start the charging, just stops the engine fan and fan relay.

With the system not charging and engine running, I disconnected chattering relays  by pulling the connectors from the relays to see if the charging would resume, it did not resume, no change, I deduct then the relays are not at fault, ( internal shorts ect)  The action of the relays results from singles coming from ECU.

I disconnected the clutch coil on AC compressor to see if charging would resume.  I thought maybe some how some type of mis directed voltage was looping through the coil back into the computer or perhaps the current load of clutch coil made the alternator come on when the AC was switched in, but, no change when clutch coil was disconnected. I could still re start the charging cycle by pushing the AC button on and then off, even with the clutch coil disconnected. The alternator would still come on with clutch coil disconnected when it came on from kick starting it.  Made no difference either way. I thought hitting the AC button caused a current draw which reminded the alternator to charge by way of the ECU but that theory didnít prove out. Finally, using the AC switch  didnít work to get it charging , drove it back from Mankato no alternator charge, never was able to re start the charging process.

More testing:
Listened to AM radio, RFI and ignition noise increases dramatically as alternator drops out; to me this indicates common ground loss but where? When charging resumed, RFI noise goes away. I tried using an ohm meter to test continuity to all parts of the areas under the hood, engine block fenders ect, as far as I can tell everything is grounded to battery. I donít know where the ECU gets its ground, its not through the screws that hold it to the fender, that needs to be checked, and also where it gets its positive power, though the 60 pin connector as far as I can tell but I didnít get to that point to check out. I would think if it lost power the engine wonít run or perform very well unless there is some default that it would.


When first trouble shooting the problem, I replaced original ECU and bought second junk yard unit and installed, this did not cure charging problem, same problem in ECU? Doesnít seem logical.

Please help me,
Sad Joe




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