74 C10 OEM Wiper Switch Part Number

[Bandit130]

Searching for the switch part number. It is the dash, 2 speed switch with push for washer.

Also would like to find a pdf file of all 74 C10 oem parts if there is one available.

[ray_mcavoy]

I believe the GM part number for the 73/74 wiper switch is 1994151.

Thanks to fellow member hatzie, you can download PDF copies of the GM parts & illustration catalogs, service manuals, wiring diagrams, and more here --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416

[Bandit130]

Thanks for the info. Wondering if the washer pump can be rebuilt? Having issues with consistent washer operation. Switch is OE so I thought it may just be old and not working correctly.

[ray_mcavoy]

You're welcome!

Yes, the washer pumps are rebuildable. Although, I think the rebuild kit for them is just a new piston seal, gasket, and end cover/valve assembly. So it might not cure all problems.

The washer pump assembly has an electric solenoid that receives power via a yellow (or black w/yellow stripe) wire whenever the key is on (a branch of the same wire that also powers the wiper motor). When the dash switch is pushed for the washer, it grounds a dark blue (or black w/dark blue stripe) wire that completes the circuit to activate that solenoid. So check to make sure your switch is providing a consistent ground on that wire when pushed.

When the solenoid is activated, it pulls in on a latching mechanism that connects the washer pump to a drive cam on the wiper motor gearbox. Once engaged, that mechanism is designed to stay latched in for a few squirts of the washer pump before automatically disconnecting. I think you'd have to buy a complete pump assembly if you find worn/damaged parts in this mechanism are causing the inconsistent operation.

The other option (if originality isn't a concern) is to convert over to an electric washer pump that's not driven by the wiper motor. Aftermarket pumps are commonly available for this ... or a more factory looking option would be to get a washer fluid reservoir with an electric pump out of a newer squarebody pickup, Blazer, or Suburban. I think they changed over to the electric pump sometime around 85.