Hi all.

Been having some issues with my electrical system. I had the "brake", "battery" and "doors ajar" lamp all on simultaneously. They would subside when I revved the engine. Sometimes they are on, and sometimes they are off. They have had an increasing incidence of occurrence over the past week. They are pretty much on 95% of the time while I'm driving now. Car shut off in traffic today too. I pulled the alternator out and had it tested at three different automotive locations. Results were all the same, alternator in good shape. I had them recharge and check the battery. Battery tested to be fine. Battery static measurement is 12.5V. While running, 12.4V. Under load, 12.2V. I traced as many wires as I possibly could from the alternator. Replaced the terminal connections and a few different grounds as well.

So my question. Can my alternator really be bad even if it tested to be in working condition at the auto-parts store? If I test the battery when the dash lamps are off, it reads 14.5V. So I know the alternator works sometimes but not consistently. Whats the deal?

 

Check battery cables for corrosion and/or loose connections.

Check harmonic balancer rubber bushing. It can sometimes come loose, slip and allow battery to discharge. For some reason, the alt light will not come on. I had this happen on a 2.5TL.

Test is to draw a radial mark across the pulley, bushing, and inner sleeve of harmonic balance/crankshaft pulley. If inner and outer sections of mark separate, the bushing is slipping.

good luck

 

When I turn the car on and observe the alternator, it seems to be spinning just fine. Would it be easier to remove the harmonic balancer and draw this line? It's a pretty confined space down there. Battery terminals were replaced this evening. So it can't be them.

 

Balancer doesn't slip all the time, only under substantial alternator load.

good luck

 

I've run across multiple pages and videos of how to test your alternator at the battery. They all say to just measure the voltage while the car is off and on. Is there a way to test my alternator with a multimeter? I got a measurement at the output pole and ground and it was identical to the battery. If I see the pulley spinning and I rev up the engine and turn on the lights, radio, heater, interior lights shouldn't I see some sort of increased voltage? How can I check the system that tells the alternator to kick on?

 

An Equus battery monitor from Walmart can be installed in cigarette lighter socket to allow almost continuous monitoring of voltage. This will show if voltage is staying too low. Voltage should stay well above 12V and typically be 13.5-14 V when charging.

good luck

 

Solution!

I visited two different AutoZone and Advanced Auto stores in addition to a NAPA for a total of five different stops. I asked to speak to the tech guy at the store. Three said it was likely my ECM, one said it was likely the dash display, and one guy told me it was probably a short somewhere. At each store I had them check the alternator. Every instance showed that the alternator was good.

Turns out, the alternator WASN'T good. I took the alternator apart and noticed that the carbon brushes had a thin coating of oil or something on them. Same for the slip ring thing. I sanded the slip ring down that makes contact with the graphite. Put it back together and put it in the car. No lights, and spec charging numbers.

 

Your problem was intermittent which are the most difficult to diagnose and repair.

thanks for posting your solution.

good luck

 

I picked up the new brush part from an automotive electronics store. It was $7.00. I'm going to remove the alternator from the car tomorrow and document the removal and install. I am also going to document the installation of the new brush on the alternator.
What is the best way to share this information with the community? Should I publish the guide on a separate web page or just do the guide here?

 

Post it here. If moderators agree on value to retain, they'll publish in the DIY forum.

Regardless, it can be found in future w/ search.

good luck