Delay module for wiper

[Wickman]

Hi all
I'm new here and I really enjoy to see how many we are that loves these trucks. I really like to work with my 1983 C20 Silverado with 6,2 l diesel. I'm just about to finish my one year frame of restoration work and at present I'm installing the electrical harness again. An improvement I would like to add is a delay module to the wipers. I found one here at the local junk yard but the pulse-mode don't work (all other operation modes work fine, but not the pulse). I have a new switch - they are easy to find - but I have really search for a new delay module, without success. The ones for 84 and up can be bought several places, but I cant find any for 183 an earlier.
Anyone who have an idea where I may find such a one?

Thank you all for all good info.

Andreas Wickman Sweden

[VileZambonie]

Try this https://www.classicindustries.com/product/sw607.html

[Wickman]

Thank you for tip, but as far as I can see they just offer the switch (which I already have) - Í miss a working delay module (connected between the switch and harness). I guess it is some electronic part broken in mine.

[VileZambonie]

Ahh, you'll have to keep your eyes open for one, as far as I know they are not reproduced. Aftermarket is another option. there are universal fit ones on the market.

[MIKE S]

That wouldn't be hard to take apart. My 87 hade the larger module that did not work. I took it apart and found a couple of cold solder joints. Fixed those and good to go. Might try it worth a shot. If you feel uncomfortable soldering find someone that repairs computers. They are usually good at soldering small circuits.

[DustyRusty]

Check the link below.  I think it is a universal model and may/may not work for your application.  Review the write-up from Scott regarding his installation.

https://store.qkits.com/wind-shield-wiper-timer-module-mxa041.html

[Wickman]

Regarding an attempt to repair it. Yes, it is very easy to open the black box, but inside its more components on that circuit board than one can understand why its necessary to have all these. No visible faults observed. It should be possible to repair it, but to be able to manage that I guess its necessary to understand how the circuit is meant to work. It seems like I have to keep looking for a used one that works.

[bd]

"Repairing" a pulse module is a matter of replacing all of the electrolytic capacitors on the circuit board.  This is because electrolytic capacitors are manufactured with a wet electrolyte that dissipates and dries over time, making the capacitors ineffective.  If you elect to do this, replace one at a time using new capacitors (caps) that have the same capacitance and voltage specifications as the originals.  Electrolytic capacitors are polarized.  Pay close attention to polarity markings (+/-) on the original caps before removing them from the board, then install the replacements in the exact same polarity orientation; otherwise, they short circuit and fail, sometimes violently.

[Wickman]

I just say "Wow". I'm deeply impressed and glad. That's knowledge! I do like the idea of repairing things instead of just throw them away. Perhaps that view is a little of the base for all of us who loves these old trucks, keep them, restore them.
Anyhow, are you so familiar with this item that you also have an idea why there is what I think looks like an IC-circuit in the middle of the circuit board? And do you no how the resistor circuit (the one you alter with the turnable knob on the switch) get positive voltage, which as I understand it must be present to make the current flow.

Andreas

[bd]

Effectively, the IC comprises a timer circuit, much like an LM555 or LM556.  The variable resistor (potentiometer) adjusted via the turn signal stalk, works in conjunction with one of the board capacitors to form an RC network that charges according to a time constant that is determined by the resistance of the potentiometer in relation to the capacitor value.  When the capacitor of the RC network is sufficiently charged it triggers the IC into a monostable mode that switches on the power transistor to pulse the wiper motor.  At that point, the park switch in the wiper motor takes control of the motor allowing the wiper to complete one sweep before parking.

[Wickman]

I can see you really know how this item works. like you were the designer. You have now convinced me, I have a buddy who makes modified computers, I will ask him to replace all (three?) capacitors. I will of course let you know the result.
Your deep insight made me curious. How can it be that you know so much about this device?

Its late now on this side of the globe. I will go to bed (so no more writing from me tonight)

[bd]

Circumstances forced the solution.  I had several modules that didn't function and were no longer available for purchase.  At the time, my only recourse was to repair them.  Upon close inspection with a bright light and magnifier, I observed trace fluid stains beneath every capacitor.  The rest is history.   

[JohnnyPopper]

Mind if I use your term; "Circumstances forced the solution"?

It applies to so many areas of life...

[Wickman]

I found this video on youtube https://www.youtube.com/watch?v=szUOZ0eCUtM&t=186s

The "frosty" item in the middle of the board, what is that?

Luckily the one on my board looks better.

[bd]

That is the power transistor that switches motor current.  The "frosty" white stuff is heatsink compound and is crucial for transistor longevity.  The compound ensures efficient heat transfer between the transistor and the finned aluminum heatsink in the module case.  Inspect the PC board solder joints using a 10X hand magnifier.  If any solder joints appear to be cracked, resolder using electronics grade, silver-bearing solder and a 5 - 7-watt pencil soldering iron.  Resolder ONLY joints that appear to be cracked, if any, so that you don't risk overheating and damaging silicon components (e.g., IC, transistor & diodes).