Here is a note from a reader who found out about broken connectors and diagnostics the hard way.


Thank you for taking the time to construct your web page. I was baffled with an electrical problem in a 1972 Oldsmobile Cutlass that I inherited eight months ago. Thanks to two of your articles in particular and the site in general, with assistance from another site ... “automotive information center” ... I was able to find and fix the problem. I gave the car to my son who is in his last year of pharmacy school in Baltimore, MD. All belts were replaced as was the alternator and battery just after I received the car. A month or so ago he mentioned the alternator light was coming on. The belt had broken. He sanded the pulley and replaced the belt so the new alternator was back in operation. Jeff did not mention the numerous times the light came back on since because the car was still running and the problem was intermittent. Unfortunately, the battery was discharged several times because of this and the fact that 1972 cars did not have warning bells when the lights were on with the ignition off as the newer ones do. One does become accustomed to relying on those bells. In the last week or so, the light stayed on constantly but was not driven very much as he walked to class and work at the local hospital.

Two weeks ago was my birthday ... of several years ... and the family convened from our various locations at Brick, NJ for the weekend. The light was on the entire trip from Baltimore to Brick, NJ and the car died right in front of Grandma’s House at midnight. The next day I looked at the system and noticed that if I disconnected the wires coming off the diodes the light would go off. I thought that was good since there was no connection then to the light. When I pushed on the “field” wire the light also went out. When I let go, the light came back on. I did not have a volt meter at my mother-in-law’s house nor did I have access to your web page. But, Jeff and I found a starter-n-alternator shop open on Saturday that checked us out. After tightening the hot wire nut he pronounced the problem fixed. But the light was still on by the time we drove back to Grandma’s. To let you have some idea how desperate we were, I took Jeff’s battery and put it into Steve’s 1990 Baretta to charge it up for the trip home. It worked but reset Steve’s computer so his car did not run as well as before the switch ... but that was an easier solution.

Jeff limped back to Baltimore in the rain without using his windshield wipers to conserve energy. Rain-X really does a fantastic job of allowing you to see without wipers in an emergency. Frustrated, Jeff replaced the battery with a more powerful one, replaced the voltage regulator and the condenser attached to it all to no avail. The light still was on and he was $100.00 lighter in the pocket book. We talked and he drove the 60 miles to my house one afternoon. My volt meter showed a constant 12 volts across the battery and the hot connection on the alternator and the light was still on. I tried to replace the diode trio but the style of this alternator was such that it did not use the black box diodes but ones that were pressed into the housing of the alternator. So I bought a new alternator. This one did have the proper pulley so the old rusty pulley was not going to wear down the belt any more. Perhaps a blessing in disguise ... but a $53.00 blessing none the less. With the new alternator installed ... the light still shone brightly. What a surprise! That’s when I found your web site and spent the next several hours reading about alternators and the electrical system of cars. The problem I had was getting to your page took several hours in it self. Believe me, you are now book marked.

I was still intrigued by the fact that I could make the light go off by pushing in on the “field” wire. At last ... in desperation ... I brought out my Sears engine analyzer that I purchased when bought a, then new, 1971 Pontiac Lemans ... when a Lemans was a car ... and replaced the D-cell battery that had been in for about 15 years. To my surprise the ohms check worked. I tested the two wires coming from the alternator to the voltage regulator. The first showed 0 ohms while the “field” wire showed infinite ohms. Why did I not believe my instincts when I saw the light go off in NJ when I pushed the wire in. I was obviously making the broken wire make connection when I pushed in and it lost connection when I let go.

Since no one will sell me a connector that plugs into the back of a 1972 Olds alternator with out the complete wiring harness ... if they had a harness ... and I did not want to rummage though the salvage yards, I bought two insulated female connectors, sized for 22-18 gage wire and removed the old plug, half of which was useless. The light went out immediately. More to the point, the voltage across the hot wire of the alternator was now 14.5 volts. I took the precaution to wrap electrical tape around each connector and then around the pair to replicate the discarded plug. I labeled the driver-passenger side of the new “plug” so as not to connect it backwards in the future.

Conclusion, when dealing with old wires, believe your instincts, especially when you are at your mother-in-law’s without your tools. After spending over $200.00 and taking the advice of some respected mechanics, the problem was solved for about $0.50.

Thanks for your help in allowing me to believe in my ability to diagnose car problems again.

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