Headlights fixed

[NavyCPO]

Well I learned something about the headlights on my monte today.  Had no lo beams, only hi beams.  Voltage checked good, turned out it actually was the bulbs.  I thought it would be something in the wiring since they were both not working, but seems that the headlights are wired in series and go through the drivers side and then pigtail off over to the passenger side.  So if you have a problem on the driver side the passenger side might not work either.  Mine was bad (corroded) contacts on the connectors and corroded solder joint on the bulbs themselves in fact one of the terminals on each bulb came right off when trying to separate the stuck on for who knows how many years connectors.  Cleaned the connectors plugged in the new halogen bulbs (auto parts store had them in stock, had to go to 2 stores.........LOL  Autozone had only one and Oreilly's had only one too, go figure).  Always change them out in pairs because they do deteriorate and get dimmer with age.  Had power to the washer pump so the button is working at the dash but pump no worky!  I think I see how to separate the pump from the wiper motor assembly, so I may try to pull it off and examine it tomorrow to see if I just need to repair the washer pump bladder or get a new pump assy. Repair kit is like 6 bucks, new washer assy is about $80.  Gonna crawl under tomorrow and measure the speedometer cable from CC to tranny.  Maybe pull the cable out and look at the gear.  Still making progress and learning new things about the car.  Pretty soon I will know her from head to toe.

[Rob Peters]

7 hours ago, NavyCPO said:

Well I learned something about the headlights on my monte today.  Had no lo beams, only hi beams.  Voltage checked good, turned out it actually was the bulbs.  I thought it would be something in the wiring since they were both not working, but seems that the headlights are wired in series and go through the drivers side and then pigtail off over to the passenger side.  So if you have a problem on the driver side the passenger side might not work either.  Mine was bad (corroded) contacts on the connectors and corroded solder joint on the bulbs themselves in fact one of the terminals on each bulb came right off when trying to separate the stuck on for who knows how many years connectors.  

Dale, In reality they are wired in a parallels fashion in that the same wire is feeding both lights.  It is just that the main feed wire goes to the plug on the drivers side connector but it pigtails off of that connection directly to the passenger side.  This would be the same as if the feed wire went to a junction box and then split off to both of the lamps.  In a series circuit it would mean that the feed wire went to the one lamp plug, through the lamp filament and out to the other lamp plug, through that lamp filament and to ground. In other words, if both headlamps were working and you disconnected the plug from the back of the headlamp on the drivers side the passenger side would still work.  Wiring cars headlamps in series would be a dangerous thing if one went out both would go out and if that were the case you would not see some cars going down the road with one headlamp out and the other one lit. 

If the corrosion was bad enough that a high resistance had caused the wires at the plug to melt the solder on the plug contact it may compromise that solder connection creating an open in the circuit which, if that corrosion was on the driver light plug may affect both lamps.  I hope this explanation makes sense to you.   

rob

[NavyCPO]

Yep, you're right Rob, it is actually in parallel.  My bad.