'72 no windshield washers, no noise either

[Gene M.]

The wipers work fine. But the washer pump does not appear to get power as there is no noise. I removed the plastic head with the three nipples. Then pulsed the switch and the piston does not move, My conclusion is no power to it. Maybe field coil is bad.....?

From looking at the wire diagram in the AIM the 18 DBL wire (dark blue) appears to be power for the washers..... correct? Or possible 18Y wire (yellow)?

The connector to the wiper motor has 18LG, 18Y, and 18LBL wires (also in AIM). I think these are for wiper function...... correct?

I looked in the old postings and did not see anything pertaining to the wiring to the washer pump. So my question is what wires do I ring out to verify input to washer pump?

[Jack H.]

Re: '72 no windshield washers, no noise either

Could be an electrical issue AND it could be a mechanical issue, Gene...

Your copy of the 1972 Chassis Service Manual provides a limited tutorial on the wiper motor and washer pump. A more 'robust' description is provided in the 1972 Fisher Body Manual...

The washer pump is electrically serviced by Yellow and Light Blue wires in the engine harness that flow back to the cockpit's washer switch via the firewall bulkhead connectors. These are notorious for developing bent pins + oxidized contact surfaces....

When the washer switch is pressed, power is fed to the washer pump's solenoid. The solenoid fires and lifts the drive prawl off the pump's ratchet drive carousel. This causes the pump piston to be driven by the wiper motor for ONE revolution of the washer drive carousel when the prawl self-parks based on a return spring.

If the washer solenoid doesn't fire, the pump doesn't run. BUT, the system relies on proper mechanical coupling of the pump to the wiper motor with the pump 'trying' to run as long as the wiper motor is running...

Remove the washer pump and flip it over. You'll see a plastic drive gear (GM nomenclature= rotor cam; mechanic nomenclature= star gear). One of the four arms on this gear has a cam slot in it.

Below in the wiper motor you'll see a metal drive pin rising out of the wiper motor's drive plate assy. That pin HAS to index into the washer pump's cam slot. If it doesn't, there's no mechanical coupling between the wiper motor and the washer. Bottom line, the pump won't pump due to loss of mechanical drive...

[Gene M.]

Re: '72 no windshield washers, no noise either

Jack, thank you for reply. I have (since making this post) removed the washer assembly. The grease was stiff. I cleaned it up and regreased it. I replaced the washer assembly using the alignment holes with a 1/8" pin to insure the engagement with the drive pin in slot. I noticed the sheet metal arm does not index the plastic wheel, causing the pump to remain always engaged now. This arm was worn so I hand filed to eliminate the groove. But this didn't help the ratchet wheel still does not index. I guess the plastic ratchet wheel has too much wear too.

I wonder if passenger cars are common on this washer pump, or if NAPA or any auto parts has a functional replacement.

[Jack H.]

Re: '72 no windshield washers, no noise either

The ONLY difference between the Corvette washer pump and a Chevy passenger car pump from the same era is the geometry of the electrical posts. Since passenger cars were made with stamped steel body panels, they didn't need the Gaussian sheilding Corvette wrapped the distributor with.

The passenger car pump has two straight slide terminals that protrude through the pump's plastic cover. That doesn't work in a Corvette environment because there's the potential for the pump's electrical contacts to short against the distributor shield...

So, the pump's plastic cover was changed to insulate the front of the electrical contacts and these terminals were made circular in geometry to accept cylindrical connectors running sideways to the pump.

Bottom line, you can go to a scrap yard, find an equivalent pump from a passenger car and 'transplant' the key components (ratchet carousel, pump piston, drive gear, prawl) onto your pump to effect repair.

CAUTION! Before you start to dissect your pump (or the donor), look at the relative position/placement of the pump's critical components. Making sketches and/or using a digital camera gets the job done...

It's REAL easy to 'space' and forget how this/that part was oriented, the prawl routed relative to the washer pump solenoid, the prawl's return spring attached, Etc. I've seen several novice to the washer pump overhaul dive in and 'muck' things up!

[Gene M.]

Re: '72 no windshield washers, no noise either

Jack thanks again, yes your caution on having assembly go back together correctly by having some "history" to fall back on is well appreciated.

I think I'll try the previous enjoyed parts yard to obtain some usable guts for the original unit. The plastic ratchet wheel and the sheet metal pawl seem to be what is needed. Appreciate the advice.

[Jack H.]

Re: '72 no windshield washers, no noise either

Enjoy your stroll though the yard(s), Gene. I keep a passenger car spare or two on hand for my car(s) to handle that just in case need...

[Erich M.]

Re: '72 no windshield washers, no noise either

My washer pump was working fine until I had to disconnect the wiper switch to do some heater core repairs. After re-connecting the wiper switch the wipers worked but I had no washers. No ratchet noise either. At first I suspected a bad terminal connection or switch. Continuity between the dark blue wire switch terminal and the blue wire termininal at the washer pump checked OK.

Removed the washer pump cover and discovered that I had a mechanical drive problem since the wiper motor was not driving the pump actuating arm. The prawl arm was also not parked back in its down position. This must have happened since the ratchet was no longer being driven.

There is 12V at both the yellow and dark blue wires at the washer pump when the accessory switch is on and wipers off. Zero volts when the ignition is off. Is this normal? I suspect that the switch is also defective since I have 12V at the washer all the time? It is my understaning that the switch is supposed to supply a short burst of 12V when the washer button is pushed to lift the prawl and engage the ratchet . Is this correct? The coil itself looks good and has a 9.2 ohm resistance.

Any suggestions would be appreciated.

Erich Meyer
Central NJ Chapter
'72 LT1 Bowtie, Original Owner

[Alan S.]

Re: '72 no windshield washers, no noise either

Hi Erich,
Original Owner; NICE!
It's very easy to put the electrical connector on the wiper switch backwards.... any chance?
Regards,
Alan

[Erich M.]

Re: '72 no windshield washers, no noise either

There is a chance and I thought about that. When I disconnected I labeled the orientation of the terminal. Its possible but unlikely. The Dark Blue terminal is now on the left side of the switch when looking from the back to the front of the car. I put a label on the top of the terminal with the word "TOP" to prevent what your suggesting. Should I be seeing 12V at the pump with the ignition on?

[John H.]

Re: '72 no windshield washers, no noise either

There is 12V at both the yellow and dark blue wires at the washer pump when the accessory switch is on and wipers off. Zero volts when the ignition is off. Is this normal? I suspect that the switch is also defective since I have 12V at the washer all the time? It is my understaning that the switch is supposed to supply a short burst of 12V when the washer button is pushed to lift the prawl and engage the ratchet . Is this correct? The coil itself looks good and has a 9.2 ohm resistance.

Any suggestions would be appreciated.

Erich -

I can't speak to the '72 specifically (although I'm sure others here can), but the midyears used the same basic circuitry, minus the complications of the wiper door system. Any time the key is on, there is power at the motor and at the pump, and both operate by providing a ground through the wiper/washer switch to complete the circuit. The motor and washer pump get ignition power through a brown wire - the yellow and light blue wires are grounded at the switch for low speed, the light blue only is grounded at the switch for high speed, and grounding the dark blue wire at the switch actuates the washer pump.

[Erich M.]

Re: '72 no windshield washers, no noise either

John,

From what you say, my voltage readings at the dark blue and yellow wires are normal and my electrical system is working properly. Am I correct that momentarily depressing the Windshield Washer Button grounds the switch activating the magnetic coil to release the ratchet. In other words although the coil terminals always have 12V, current does not flow through the coil unless the Windshield Washer Button is held down. When you take your finger off the Windshield Washer Button no current flows through the coil and the electromagnet is de-activated.

Seems like I should repair my mechanical problems and see if the pump works with the existing electrical system.

[Terry M.]

Re: '72 no windshield washers, no noise either

Erich,
There are two common problems with the wiper/washer systems on early C3s -- maybe later C3s as well. One has already been mentioned = putting the connector on the wiper switch backwards. The other is the lack of ground continuity in the instrument cluster. It is common for these clusters to break right above the gauges and when that happens the wiper switch no longer has a ground, or that ground is intermittent. Obviously when the housing is no longer grounded none of the wires can be grounded by the switch. Run a small jumper wire to the wiper switch surround to the birdcage (easy if you already have the passenger side dash pad (the one with the pocket in it) out of the car. The instrument cluster is designed to break at this point to prevent injury in an accident, and the Chevrolet Service Manual has a bold cautionary note about this "feature."