Wiper motor always on.

[Havasu]

Hello all,

On my '83 Suburban Silverado, with intermittent wipers; any time the ignition is on, the wipers stay on. I've done a search for other threads about this issue but none of them had a resolution or they weren't about my model year truck. The wipers worked correctly previously, and nothing electrical or in wiring was changed.

I have already purchased a new wiper switch and this did not correct the problem.

I read in other threads about a pulse module involved with this system, but I haven't been able to find it in my truck.

Could the pulse module be the problem? Does this model year even have one? And where should it be?

Thanks so much in advance for any help or tips you can provide, please!

Marie

 

[bucket]

Yes, it could be a bad pulse module. The wiper switch plugs into it, which in turn plugs into the truck harness.

You can remove the module and plug the switch directly into the truck's harness and see if the problem still exists. The problem likely will be gone, but you of course will not have a delay feature.

 

[Havasu]

Thanks bucket, appreciate the reply!

I did bypass the module this way and the wipers work correctly, albeit without the delay feature.

I work in electronics so I'll be trying to rework the delay module, as replacements don't appear to be available. Thanks again for your help!

 

[wlwarnke]

Thanks bucket, appreciate the reply!

I did bypass the module this way and the wipers work correctly, albeit without the delay feature.

I work in electronics so I'll be trying to rework the delay module, as replacements don't appear to be available. Thanks again for your help!

Any update on the reworked delay module?

Also, how’s the new switch? I’ve been tempted to get one but worry about quality as I’ve heard they kinda suck.

My switch works, but occasionally has trouble differentiating between off and delay.

 

[Goldie Driver]

Any update on the reworked delay module?

Also, how’s the new switch? I’ve been tempted to get one but worry about quality as I’ve heard they kinda suck.

My switch works, but occasionally has trouble differentiating between off and delay.

Assuming 83 still uses the dash switch, the LMC new one worked fine for about a year and then got "sticky" , meaning you could not help shooting past off and it getting hung on the mist side (left most position).
No big deal, just had to push it back right.

I lived with that for 3 years - put my OE back in last time I was in the dash.

The LMC one came with the black knob, BTW- I did not know that and bought a 10 dollar knob as well.

Save your 10 bux.

 

[R Carnella]

I had the same problem on my 90 suburban and yes the module was faulty. I think they all fail at some point because finding a good used one is hard to find. I bought one from rock auto about 3 years ago and they've since disappeared from from the site

 

[R Carnella]

I ran a switch to the wiper fuse for awhile before i fixed it.

 

[Havasu]

Any update on the reworked delay module?

Also, how’s the new switch? I’ve been tempted to get one but worry about quality as I’ve heard they kinda suck.

My switch works, but occasionally has trouble differentiating between off and delay.

The new switch seems alright, but I suspect the PO put a new one in there also at some point, as it looks exactly the same and also has a black knob. The new one came with a new lightbulb socket also.

I've managed to identify all the components on the circuit board except for the Motorola IC chip and what looks to be an SCR or a MOSFET. I may get lucky plugging the SCR into one of my testers to identify it, but the identity of the IC chip has eluded me so far.

Life is getting in the way of further progress with this, but I'll post what I find out.

 

[scrap--metal]

Life is getting in the way of further progress with this, but I'll post what I find out.

Please do keep us updated with any future progress. I'm also interested in knowing what it takes to rehabilitate one of the delay modules. Pictures would be appreciated as well!

 

[Snoots]

The new switch seems alright, but I suspect the PO put a new one in there also at some point, as it looks exactly the same and also has a black knob. The new one came with a new lightbulb socket also.

I've managed to identify all the components on the circuit board except for the Motorola IC chip and what looks to be an SCR or a MOSFET. I may get lucky plugging the SCR into one of my testers to identify it, but the identity of the IC chip has eluded me so far.

Life is getting in the way of further progress with this, but I'll post what I find out.

I've shelved mine for a while since I got frustrated but my last notes showed a IRFZ44N MOSFET as a likely SCR. It could also be a Thryistor. As I said, I didn't want to throw $$ at it so I had to cool off.
The chip I believe is a 4001.

 

[Snoots]

Marie,

This is all your fault!
I found the p/n of that darn SCR. BT145-800R. No one I've found has it, it's backordered; even at Mouser. Unless you want to buy 5000 or so, from china.

 

[Havasu]

LOL

Oops, I didn't see this post before I sent a message to you, Roger

Yeah, it's going to be an Easter egg hunt finding these components. Thank you for the part numbers, I'll see if I can also find another source.

There are enough people looking for a solution for this, it would be nice to give back if we collectively found a full set of components to fix the darn thing!

Marie

 

[R Carnella]

Solving this issue would benefit the entire community.

 

[Havasu]

Posting a pic of the delay circuit board on my truck, 1983 Suburban Silverado C20. The wires go to the jack and plug that splices this into the wiring harness.
To the left side of the pictured board is where the delay switch plugs into tabs on the board.

I've encountered at least three different physical versions of this board GM used that plug into the vehicle differently, and each of them seem to have at least two part number substitutions along the way before they became obsolete.

This seems to be the most basic physical version of the board, with only one IC chip and one semiconductor/thyristor/SCR. Other versions of the board have different IC chips, one or two transistors as well as the SCR, and a different physical connection to the wiper/delay switch.

My point is the EXACT solution will vary depending on what version delay board you have and what your symptom is. With further input from others who have different boards and different symptoms it might be possible to create a generic kit that fixes an overwhelming percentage of those problems, but unless we figure out an effective substitution for the IC chip it will be the biggest stumbling block to creating a 100% effective kit.

I have managed to pull the SCR on this board and it tests good, that's the black component with three legs in the bottom left of the picture. I suspected it first just because it has such a cheesy heat sink to cool it, and my symptom of an always on wiper no matter what position the wiper switch was in would suggest a permanently switched on SCR.

The diodes, resistors and capacitors on the board help create the "delay" we get, depending on how many are switched into the circuit with the SCR.

I have seen digital logic drawings for two different IC chips used on this board and it seems to be responsible for switching in how many delay components from the board are used, according to what the delay switch position is. I'm ruling out the IC chip for now just because it's a very low voltage logic component and I can't even find a suggested replacement for it.

I've ruled out the resistors as a last resort since there are no overheating indications for any resistor on the board.

Since the SCR tests good, two different switches didn't change anything, and the symptoms don't change regardless of the switch position; I don't think it's the IC chip and this leaves either the diodes or the capacitors. They are common failures in any circuit and at the very least they're easiest to find and replace. Moving forward....

 

[Snoots]

Workin' on it.
Those electrolytics are ~40 years old.