Hey fellas, we are having a weird intermitten wiper issue on our 427 car. When you hit the switch, the wiper door opens correctly, but no wipers. So I started checking around the system and found something weird I don't understand.

1)If I disconnect the big plug behind the distributor with the 2 red/white wires going in and out(to the wiper door safety switch) and jump the wires across on the harness side, the wipers work fine. So common sense would tell you the wiper door switch is bad. BUT if I use the DVM to check continuity when I manually push the botton in on the switch, I get continuity fine telling me the switch is working fine.

2) I made a set of jumper wires with female on one end and male on the other to connect both sides of the plug(the big round plug that goes to the wiper door switch) together without having to have them plugged into each other. So I tie the constant 12v wire on the harness side to the corrosponding side on the switch. Then I test for power coming out of the switch when I push the little button in, test good, got power. So I add the jumper wire to the other side of the plug on the switch side and check power at its end, test good have power....BUT as soon as I plug that lead into the corresponding wire on the harness side, I suddenly lose power(when pushing the button in). If I unplug the jumper lead from the harness side, I have power again.....but I'll be damned if I plug it back in completing the circuit and it goes dead....Almost like something in the harness is killing the power to..


I know this is very long and drawn out but....just looking for something to check...Every now and then they start working fine for a couple of times, then nothing. But the wiper door always works, the 12V constant to the wiper motor is always hot, and the 12V constant to the wiper door safety switch is always hot...Thats telling me the problem is on the harness side. I am assuming thats the power that goes to the relays and what not...

Anyone got any ideas?? I checked a wiring schematic and it gave me a headache.

 

Do you know for sure that the switch is adjusted properly so that it is fully "made" during normal operation? Just pushing the switch to see that it works is one thing; knowing that it is actuated fully under normal use is another thing altogether.

 

Yes the arm is making full contact with the switch. Like I mentioned, I can get power in and out of the switch, its when I plug that power back into the harness that the power dies.

BTW
1) Wiper on/off switch--NEW
2) Overide ****/switch--NEW....and we tried jumping the plug also just because.



We also tested my 71 and even when the key is off but the bypass is pulled for the wiper door to be open, I have power from the harness, to the switch(wiper door safety switch) and from the switch, back into the harness(tapped the side of the wires with the volt meter and has constant 12V when the door is open)


On the 69, its something in the harness...its like its grounding that power out or something. Something intermitten. I am thinking its a relay, maybe the one under the console or a bad ground or something.

Oh the bezel is new also and not cracked so the wiper switch is grounded well. Plus the wiper door opens and closes well with the wiper switch so I know its making good contact.

 

This test should rule out everthing except the switch and the wiring connected to the switch and the 2 connectors you plug into the switch----It sounds like its in the connectors in the big plug.

Grounds can make them act odd-run an extra ground to the wiper case and to the block.

 

Quote:

Originally Posted by DWncchs

This test should rule out everthing except the switch and the wiring connected to the switch and the 2 connectors you plug into the switch----It sounds like its in the connectors in the big plug.

I thought it was the connectors in the big plug also, thats why I made the two jump leads with the female/male connectors so I could effectively hook the two plugs together without plugging them into each other. As soon as I plug the 12V side from the harness into the switch and press the button.....BOOM, I have power coming out of the switch....As soon as I plug the outgoing wire from the switch back into the cold side of the harness, I lose power right then...Thats where there is something weird going on, that circuit should be hot all the time as long as the wiper door safety switch is depressed.

But if I pull all the leads off and just stick a jumper wire from the 12v hot side on the harness plug to the cold side of the harness plug, the wipers come on and work fine. Common sense tells you that would be something with the switch but the switch tests fine with continuity testing and voltage output testing. It works fine until I plug it into the cold side on the harness then its dead as a doornail.

 

Anyone have a wiring diagram of just the wiper circuits? I have the doc rebuild thing and its got too much junk on it. I need something simple...much like the vacuum system diagrams floating around...

I know there is at least these parts:

1)Wiper switch
2)Wiper relay(under console)
3)Wiper door vacuum solinoid(behind tach)
4)Wiper override ****
5)Wiper door safety switch
6) Wiper arm safety switch(in the wiper tray area)
7)Wiper motor

Just not sure how the wiring works and how the circuit flows....

 

 

My diagram spans 5 pages and its pretty worn out so I dont think it would scan well.I looked back through the archives but could not find any diagrams like you want-basic without the extras.
Below is a thread about wiper motors- check the long post-its down about 6-8 posts-by Mike.It might help a little bit.I'll keep trying to find what your looking for.I did see in one of the old posts an [IMG] to a 72 diagram but it didnt work.That post was by Shafrs3-Maybe a PM to him might turn one up.

http://forums.corvetteforum.com/show...um_id=3&arch=1

 

THANKS DW......I will check out that thread....I have been searching but its like needle in a hay stack.... SOOO many wiper threads...

 

Here is the closest I have its a 71.I still think you have already narrowed it down but this might help anyway.
I have a quick question.I took this out of one of my Word Document files.I could not copy and paste it to the post.I had to scan and copy it and save as a picture so Photobucket would let me upload it.How can I skip the scan and copy steps?Help !!

 

THANKS A LOT DW!!!! I will start studying that thing and see what I can figure out.... I hate this crap...

 

Your welcome.
I just thought of another idea since you have some jumpers.Try running another motor "through" that limit switch and its wiring pigtails and see if it works ok.If that motor fails that would put your wiper motor in the clear.
(I'm not sure what that switch is out of its not automotive though.I believe its a 110-220 volt switch-probably out of a washing machine. )

 

Most DVMs will give you a good continuity reading for anything below 100 ohms. Test the Resistance. With the leads and minor contact Res, it should read no more then 1/2 an Ohm (0.5 Ohm). Could be dirty switch contacts. You will also read full voltage through a high resistance (dirty) switch contact, untill a load is put on the switch.

 

Try using a real load like another motor or a headlamp. It may be that switch contacts are burnt or corroded and will not handle the current, causing the voltage drop you see.


Joe

 

I just had a brand new home light switch do that. Continuity through the switch, but no light. Returned it and got another that was fine. Never seen that before, name brand switch too.

 

OK guys....I will try hooking a little light bulb or something up to the output side of the switch and see what it does.... That would make sense.. LIke I said, I put power to the switch, then push the button in, I can get 12.6v out of it but as soon as I plug that very lead(one with 12.6) into the harness, it goes dead. I couldn't imagine what would cause that in the harness...

Sometimes it works, sometimes it don't. It makes perfect sense though the switch dropping out under load. I will take the switch off the 71 and put on the 69' and try it. I will let you know what it does.

 

Here's your switch and if you click on it you can see a cutaway.Its 15amps.If you need one you could contact Cherry and see who they sell them to in your area.I think that switch is pretty expensive through a dealer.15 amps-Does a blower motor draw that much? Maybe you could run that through it to load test it.
http://www.cherrycorp.com/english/sw...neral/e_sp.htm

 

I am gonna go to my dad's this weekend and slap the switch from my 71 into his 69'. I believe thats the simplest test...I know my wipers work well. Then we will go from there.

I really appreciate all the help. I will post up the results this weekend.

 

Well you guys were right, it was the wiper door safety switch...I swapped the switch from the 71 into the 69 and the wipers worked fine.

Just for $hits and grins, I tested the switch off of the 69' again with the DVM using both the continuity test and actual voltage test and both tested out OK... I didn't try to "load" the output side of the switch with anything but the problem was definetly switch related internally...Like you guys suggested...it must be a contact point problem under load that breaks circuit.

Anyway, as always, thanks for the help...got another one up and runnin.

This forum kicks a$$.