Headlights (lowbeams only) and washer pump failed at the same time (perhaps?)

Hey,

I'm wondering if anyone has any insight about what could be a common cause for the headlights and a washer pump to fail at once. I'm in the middle of troubleshooting it but it's cold outside and not exactly fun to work out there.

Yesterday I started it up and when I went to put on the headlights they flashed for a second then immediately went out and won't come back on. Fog lights are fine, highbeams are fine.

I noticed today my windshield washer pump isn't working either, I don't know for sure if it failed when the headlights failed but I know it was okay fairly recently. It's not making any sound so I don't think it's a clogged hose.

Things I've checked so far:
Fuses for the headlights and the washer pump are good. Verified with a multimeter.
Relay for the headlight is good. I verified it with a 9V battery and a multimeter.
12V verified at the headlights plugs.

Things I haven't checked/done yet:
Power at the washer pump.
Grounding issues. I'm not totally sure how to go about it or where they may be a common ground for these two systems.
Replaced the bulbs. They're expensive and I don't want to blow a new pair of bulbs if there is still an issue which blew the existing pair.
Tested the lights and the pump directly somehow, not sure how to directly connect them.

It seems odd to me that no fuses blew, isn't that what they're there for? So I don't have to buy new headlights and a washer fluid pump? I am sort of hoping there is a ground break somewhere and the lights and pump are in fact still operational.

Any help would be appreciated.

Thanks! (First post, hi!)

 

Do you own a test light?
We are going to need to test the ground.
And test the circuit’s ability to carry a load.

 

Easy first step is to see if the headlight indicator on the dash comes on with the low beams.
It uses a separate ground.
But uses the same power.

 

I don't have a test light, but I do have a multi-meter.

The headlight indicator does come on properly. I did a bit more probing yesterday and what I found didn't really make sense to me so I'll have to write it down to post here. It seemed the grounding changed depending on whether the switch was on or not.

When I probed the washer fluid pump there was no power to it (I had someone activate it from inside.) Interestingly when I probed one of the contacts, the wipers came on, but perhaps that's to be expected?

 

The head lights are grounded by 2 different ground locations. (redundancy for a backup)
And it would be off that they are both bad.

However, the Washer motor uses only one ground location.
1and it is one of the same as the headlights.

The White/Black wires are the ground wires for both the Headlights and the Washer pump.

Since you don't have a test light.
See if you have 12v between the Red/Yellow wire and the White/Black wire on the DRIVER'S side headlight.

Do the same for the Washer.12v between the Blue wire and the White/Black at all times with key ON.

 

It has warmed up a bit, I'm no longer busy with Christmas, no longer sick and I've got the truck off the street and into the garage to do some more testing.

Latest testing results:
Confirmed both headlights lowbeams are blown, but the highbeam filament is still good.

Headlight probing on both sides are the same:
* 12v between highbeam power and ground with highbeams on.
* 12v between lowbeam power and ground with lowbeams on.
* 0v between lowbeam power and highbeam power with highbeams on.
* 9v (huh?!) between lowbeam power and highbeam power with the lowbeams on.

I get 12v between the two slots of the washer plug when I activate the washer from the cab, 0v otherwise.
I get 12v between the power slot of the washer plug and a grounding location on the vehicle at all times when the key is on.

I don't want to replace the bulbs or the washer pump until I'm sure they aren't all going to be fried again. Is that 9v between the two power prongs of the headlights unusual or not? Where should I look next? I do hear a slight electrical hum in the engine bay when the key is in the on position, but that's possibly normal too.