Good logical diagnosis.
Good logical diagnosis.
Early S Registry member #90
R Gruppe member #138
Fort Worth Tx.
What was unlucky was that the Instrument lights connect via Blue/Black to Tab 58a on the light switch. Unfortunately, tab 58a and 57 are connected within the light switch. 57 is important as it send power to the Changeover Relay at pin 86 which then causes power to go to relay 87a and the High Beams.
Because Relay 86 needs 12V power to trip the magnetic coil, the short of the instrument lights caused a loss of voltage at 57/58a on the light switch which in turn caused a drop in volts to 86 on the Relay. With the short fixed, Pin 86 was at a full 12V and power was sent to 87a and on to the fuse box and the High Beams. I retested this theory with the dash light bulb shorted and found only 7 Volts at Relay pin 86, not enough to trip the relay. So that was the root cause.
1968 911L Coupe - Golden Green
1971 911S Coupe - Gemini Blue
1973 911S Targa - Signal Yellow
1974 914 2.3 - Sunflower Yellow
Great perseverance. How many PFUs are you charging yourself for diagnosing and correcting this problem?
Imagine if we didn’t have this board for advice !Originally Posted by ejboyd5
1968 911L Coupe - Golden Green
1971 911S Coupe - Gemini Blue
1973 911S Targa - Signal Yellow
1974 914 2.3 - Sunflower Yellow
Different car but same problem. Eight years ago I purchased a Classic Mini Cooper in SFO. The fellow I bought it from said he had a mechanic look it over since I was going to drive it back to Oregon. Should have looked it over myself. On the way home it handled terrible in the turns and as the sun went down I found out I had no headlines. I had high beams when I pulled the flasher on. Soo, I drove home holding the flasher on steady a mile and a half behind a semi. The headlite problem was in the column and the handling was 5 lbs of air in the rear tires!
Kent Olsen
McMinnville, OR
72 911 upgraded 3.0L
RGRUPPE # 104
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