78 Chevy K10- Intermittant wiper switch issue

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DSS

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Dan
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1978
Truck Model
K10
Engine Size
350 V8
My 78 Chevy K10 has the OEM intermittent wiper switch module- It has been working fine until recently where the washer function not will either:
1-Not work at all
2-Come on and stay on at every wiper speed setting (i.e int,slow,fast)

Any one else out there have this happen? Is this sounding like I need a new int switch and/or the module?

Thanks for any assistance!
 

chengny

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K3500
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So in situation 1:

When it's time to wash the windshield, you push the button and get no reaction at all - the pump doesn't squirt fluid and the wipers do not make 10 sweeps at low speed. Correct?

And in the second case:

It's raining and all you want to do is clear the windshield - not squirt fluid on it. So, you select the desired constant wiper speed (hi/lo) or the intermittent mode (lo only). You do get wiper operation as selected. But not only do you get wipers, the washer feature activates and begins to pump fluid. Correct?
 

DSS

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Actually the wipers work fine in both cases as they should in the various speeds- it is the washer function that has gone haywire- it either wont function when I press the knob, or it will stay on, and keep squirting at all wiper speeds until it either runs out of water in the reservoir or I turn the wipers off

Thanks
 

chengny

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Here is a brief description of pump operation:


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Diagnostic procedure for a pump non-stop condition:

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And a dwg that shows which harness plug to pull when doing the diagnostic:

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Basically, what the diagnostic tells you is whether the problem is within the actual wiper motor assembly - or if it is a problem in the switch/wiring. You don't want to buy unnecessary parts, so do this first before anything:

1. Get the pump to go into it's non-stop operation.

2. While it is still pumping uncontrollably, go out and pull the harness plug as indicated
above.

3. If the pump stops squirting - the issue is in either the switch or the associated wiring.

4. If removing the plug does not have any effect (i.e. the pump operation continues),
the issue is internal to the wiper/pump assembly.


Apparently, the pump is not serviceable as a separate component. So if the problem is within the wiper assembly, you'll have to buy a new one.
 

bucket

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Had that happen before, it's the switch. The "push" part of the knob function gets gummed up and/or burned. Disassembling the switch to clean/lube everything worked on mine.
 

DSS

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Did the diagnostics and naturally it is the washer/wiper pump assembly- not the switch
Oh well- Appreciate the help
 

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