What is wrong with my wipers - Lots of testing done and I am stumped

[goathearder]

So while I am waiting for the stuff to rebuild my front driveshaft, I thought I would re-hook up the wiper arm linkages. Go those all hooked up by my wipers won't turn on!

I went online and found out how to bench test a motor (hot to middle terminal and ground to 1 or both outside terminals. That works perfectly so the motor is just fine.

When I take the switch out by itself and put 12v to the middle, it seems one outside terminal always reads 0 and the other outside terminal reads 12 or 0 depending on the position of the switch.

However, and this is where I get all confused, when I connect the switch back in the dash and plug the motor in, all 3 terminals have 12 v ALL the time regardless of the switch position. Clearly that is why the motor isn't working cause it needs ground for at least 1 of the outside terminals but I can't figure out why all three are hot all the time? Should the motor have an extra ground to it? Is my switch bad? Any insight would be very helpful.

SOLVED - see post 12

 

[andyblack]

Sounds like a bad switch to me. I've never heard of a problem quite like yours though. Has the wiper motor ever worked since you've had the truck? You haven't been doing any wiring in that area, have you? When something goes bad on my truck, the first things I suspect are the things I've worked on, no matter how long it's been.

Also, look for a loose ground wire(s). I know there's a couple that are around the dash and column and if they come loose and/or get corroded, they can wreak havoc on headlights, dashlights, etc. I would actually look at this first, since you've checked the switch and it looks good.

 

[goathearder]

I've only had it like a month and the linkage was disconnected since last night so I never tried the motor and havent done any wiring or messed with anything in that area at all. I will have to look at grounds and I'll probably just get a new switch I guess.

 

[andyblack]

Oh crap. I bet the previous owner (PO) did some auxillary wiring. I've had my truck for 5 years and still have yet to figure out the way my truck was rewired under the dash in its former life. I have to keep one of the fuses out so the battery doesn't drain overnight due to the PO's crazy lighting job. Fun times.

 

[goathearder]

Oh man, you can feel my pain then. There is some crazy stuff under the dash but all the wires for the motor look clean. There is definetely some sort of alarm system down there that doesn't work and who knows what else.

 

[goathearder]

Ok, I have been doing a lot of reading on the internet (Wilcox corvette has some great articles and the same style wiper motor as the Blazer) and it looks like there might be a ground wire to the case that I could be missing?

Could someone out there take a picture of their wiper motor and post it so I can see all the connections? It needs to be a Blazer with the 3 position switch and NOTthe control in the steering column.

Thanks!
John

 

[GMC Truck]

Does it have a delay switch (knob rotates)? If so you can remove the delay module (its inline) and just plug the wiring back into the switch without the module. The motor is case ground and has a "strap" on one of the bolts.

 

[goathearder]

No, no delay but I definetely don't see a strap on one of the bolts. You wouldn't happen to have a picture of said strap would you?

 

[max 02]

No, no delay but I definetely don't see a strap on one of the bolts. You wouldn't happen to have a picture of said strap would you?

I`ve been watching this thread because I got the exact same problem.
I did have a 8o wiper motor on my truck wired to a push pull switch. That worked but is totaly homo. I didn`t have a motor that worked for my truck untill now, so I wanted to get it working factory, its just not happening yet.

I can`t remember ever seeing a ground strap for the wiper motor.

 

[goathearder]

I hear what you are saying about the switch. I am so frustrated at this point I am thinking of having two switches for each wire that needs ground just have working wipers. I would rather have the factory switch but I just need them to work.

 

[max 02]

I hear what you are saying about the switch. I am so frustrated at this point I am thinking of having two switches for each wire that needs ground just have working wipers. I would rather have the factory switch but I just need them to work.

If you are ok with a switch, that is easy. just run power from the battery threw a fuse to the switch back to the wiper motor, and then a ground from the motor to the truck. But you will have only one speed. and no washer.So then you gota do the same thing for the washer.
I had mine this way for two years, but my truck is just a yard beater. and it is not insured.WHEN I get it the way I want it I`ll get it on the road. My wireing is chopped up under the dash from po,I Got a couple of spare harneses, so when I get mine figured out I`ll let you know.

 

[goathearder]

Ok, as if some miracle has occured I have solved this. Last night I put the switch into the off position, turned the key on and read 12v at all three terminals (like I knew I would). I then shorted the rightmost terminal to a bolt holding the motor to the firewall and it worked like it was supposed to. I already knew the motor worked so this wasn't a huge shock though.

Then, I put the switch into the low position to try this again but much to my surprise the motor was working!!!! Put the switch in high and the motor was still working!!!!

Given all that, here is my theory and hopefully this can help anyone troubleshooting in the future:

The motor is grounded to the firewall by the bolts that attach it. In my case, the bolt holes had paint in them from a recent paint job so I don't think the bolts were getting good ground. Shorting directly to the bolt heated it up enough to clearly out the paint/grime that was in the bolt hole and now it makes good contact.

I know that might sound weird but I can't think of any other reason it would have started working correctly. Anyway, I hope this can help someone out!

John

 

[andyblack]

Glad you figured that out. That was a frustrating problem, no doubt. I'd say that missing grounds cause more electrical problems in DC circuits than other thing. Good work!

 

[max 02]

Glad you figured that out. That was a frustrating problem, no doubt. I'd say that missing grounds cause more electrical problems in DC circuits than other thing. Good work!

Glad you got yours working.I don`t think mine will be so easy, I think the guy that had it be for me was having probs with it by the way eveything is hacked up under there. But I got 2 good harneses and lots of factory switches so I`ll get it figured out as soon as I got some time to look at it again.