Okay, I swapped out the regulator for the original and it works beautifully. I guess since I cleaned up the internals of the alternator, it is now putting out good charge. In fact, voltage at the hot post reads over 12.5V at idle under all but the worst conditions (A/C on max, rear defroster, headlights, brights, windshield wipers all on). I would say that for most common loads, the alternator is now charging fully at idle, and when I blip the throttle with all the accessories on, the voltage jumps above 12.5V, indicating that the battery is not discharging. I guess I just got a bad regulator, and the cleaning of the alternator fixed the problem. However, now my oil pressure gauge is behaving strangely. It was working fine for a while, so I left the car in the driveway to idle while I was cleaning up. When I got back in to turn off the car, the oil pressure was pegged at 5, although the car was idling and the engine had reached appropriate operating temperature. I turned off the engine, and the needle stayed stuck at 5 bar. A thump on the dash dropped it back down, but when I turned the key back to the "on" position, it shot right back up to 5. This is the symptom that my sending unit displayed when it failed, but as I mentioned earlier, this unit is brand new with only about 5k miles on it. Is there any other problem that could cause the oil pressure to peg high? I did, as mentioned, replace the oil thermostat. Is this somehow normal behavior? My impression is that it is not, but I'm sure the sender is wired correctly, and it should be functioning just fine.

 

Alan, I think I must have read that somewhere about american cars and not realized that it was an band-aid fix and thus not the normal condition for all cars.

 

the voltage readings are too low , you probably have a bad diode in the alternator

 

You seem to be confused again.

Nominal Battery Voltage is ~ 12.6v - this is battery only engine not running no load

System Voltage (measured at the same places) is when the car is running and the Alternator is doing the power generation (and recharging the battery) - it should be approx 13.5 - 13.8v. if it is a lot higher than this - its a problem. It should not be lower than this at 1500rpm with any equipment turned on.

It may droop at idle when you have lots of equipment on - but if its droops to lower an 12.6v - you are depleting the battery (e.g. it the alternator is not keeping up with required power and the battery is supplying at least some of the power - eventually it will totally discharge if this condition persists for too long...

Alan

 

On the oil sender - are you sure you wired it correctly - the 2 wires on it are not interchangeable.

Alan

 

Well, I let the car cool down for about 30 minutes and went to check it out again. I turned the key to the "on" position and the needle hopped up to 1 bar and didn't climb higher, so it would appear that maybe the problem is intermittant? Also, yes, I'm sure I've wired it correctly. Also also, the battery voltage is about 12.6, but with the alternator running with the bad regulator, it was reaching ~15V at high RPM. I swapped out the regulator for the original (after cleaning the unit up) and the voltage was rock steady at 13.8V, with some drops when accesories were turned on.

 

voltage reading sounds correct.

Replace the sender, if the wires are in the correct positions and not shorting/touching each other

 

Does the sender fail intermittantly? I have a feeling the problem is in the gauge. Occasionally at idle I will get a low oil pressure warning light and just now I took it out to reaim my headlights I got one. The difference this time is that the needle read 3 bar instead of near 1. Normally when I get the idiot light then needle reads just above 1. Also I noticed that gentle driving was producing pressure of around 4.5 and any more would peg the needle at 5. Before I had been stable at 3 to 3.5 for most driving conditions. By the time I got home and parked the car, the pressure was reading around 2 bar at idle and no idiot light, just like normal. I feel like that implies a fault with the wiringf to the gauge or the gauge itself and not the sender. Am I off-base here?

 

you said that you replaced the oil thermostat that means that you had to remove the sender, if your sure the oil thermo springs are correctly installed then you may have damaged the sender in the removal process

 

The pressure should be 5 bar pegged at cold idle and also at over 3K rpm it should pretty much always be pegged at 5 bar. Hot idle should be about 2 bar. Best not to try to replicate previous behaviour that was just wrong.

Alan