Voltage spike at low beam socket (bad LCM?)
I just found some very interesting test data. I was testing the load response on the charging system (at the low beam socket) when the car was cold (at idle approx. 500RPM) voltage started out at 14.25 (everything off) turned on all accessories voltage started to drop, when down to 11.2 (less than 2 min) engine began to “shudder” then the rpm kicked up to approx 850rpm. Voltage went to 13.8 and was steady. During this testing I turned off and on the headlights (and to my surprise) DMM read OL then >20.5Vdc then to 13.8. Repeated this sequence approx. 15x’s (same results) however after the 15th or so cycle voltage STOPPED peaking, and I cannot repeat the same results (I am starting to think a bad/wet LCM). In addition, I also measured voltage decay (using the OBC test 9) with the engine off. Voltage starts at 12.5 (right after turning engine off) then quickly drops to 11.7 (nothing on). Then starting turning things on (parking lights, radio, interior lights, REST button) voltage dropped to 11.2 and stayed there (longer than 10 min). I am not sure (at this point) if the battery is responding properly, I don’t think the voltage should drop as low as it does, and then hold steady at 11.2 (bad cell?). Also I don’t know what a CEL is. Again all comments/suggestions are (and have been) greatly appreciated!