Hello everyone. I just purcahsed a 1974 Corvette from "bubba" I have been reading on the forums for the past few weeks and it seems that Bubba has owned a few corvettes in his days.

But anyways, I was having issues with the wipers not working. Read on the forum were that the wiper motor needs to be grounded to the bell housing. My setup had three wires(with round connectors) going down to the starter. One main power, one red, and one black. It also had the one for the selonid. So i read on the forum a guy had the same problem with with the blower motor and wipers not working because all three wires were hooked up to the positive side of the starter. Well, mine just happened to be hooked up the same way. So, I grounded out the black wire to the block and that didnt fix the problem. Infact, that wire had 12 volts running through it when the ignition was turned on. So i just created a short circuit. So, I took that wire off of the starter and moved it out of the way. I also made a short jumper wire and grounded out the wiper switch to the center console. I tested the wiper motor and it worked. (thanks to Wilcox). Now here's the deal. I got everything working with that setup. Black wire disconnected from the starter and wiper switch grounded out and the hood on the car open. Everything worked like a charm. So i figured I go drive the car up to the store. I get there and turn the wipers on and they dont work. So i go back home and start messing with it again. Open the hood up and guess what? The wipers work. Can someone please explain that one to me? If i press the switch down for the hood alarm (that what I am assuming it is) (the switch close by the starter interupt relay) the wipers stop working. If i leave the switch open, they work. My blower motor still does not work though. Any thoughts???

 

Raceman,
Of all the things I'm dumb about I'm dumbest about things electrical. Sorry, no help. But...as a new Corvette owner, I'd suggest you get the GM Chassis Service Manual and the Assembly Instruction Manual (AIM) for your car. Bubba can't read so he doesn't use them but they'll be a BIG help to you as you work on your car.
Regards,
Alan

 

I already picked up the wiring diagram and have been using it to some extent to help me sort though Bubba's mess. The car also came with the how to tear everything apart and put it back together manual Bubba gave that to me because he said he couldnt read (like you mentioned). Im gonna go do some more investigation now out in the shop. Any suggestions are welcome.

Thanks
Aaron

 

Aaron,

You definitely have something wired wrong. If the hood is closed and collapsing the alarm switch, then the alarm switch is being used as a ground on the wiper circuit.

This is not correct!

The hood alarm switch is a ground for the alarm system only when the hood is open. (thus creating the ground needed to sound the alarm).

Your car is a 1974 but the wiper system is pretty much the same as the 1972 and back systems.

I do not have a schematic on the web site for your wiper system, but I will try to make this simple for you.

The middle wire on the three wire connector is the power wire for the operation of the wiper motor. The two outer connectors are the ground for high and low speed.

You should have a main power wire and a main ground wire for the motor power on the two field set up used by this motor.

If the alarm switch being closed is cutting off the ground you need to track down why the ground on the alarm system is in the circuit with the wiper motor.

I’ll look at this closer when I get a chance and post or email me direct and well figure this out. Willcoxcustomerservice@willcoxcorvette.c om

Willcox (with two L’s).

 

I was messing around with the system last night trying to figure it out. I removed all the door adjar and door security micro switches and cleaned them. The Drivers side button (the one down by the pedals not the one by the seat) had one wire that was not attached. I reattached that wire. The micro switch by the seat on the passanger side was also stuck pushed in. I fixed that problem as well. Now, nothing works requardless of weither or not the doors or hood are open or closed. When I press in on the wiper switch (to turn on the wiper fluid) I can hear a clicking noise coming from the wiper motor. I assume its a relay. I will check tonight and see if I am getting power out of the harness on the middle connector to the wiper and motor and check the outsides for continuity with the chasis ground.

Can someone confirm or deny if the small black wire going down to the starter location actually goes to the starter or does it need to be grounded. If it needs to be grounded then, that is were my problem lies because it is showing 12 V when the ignition is on.

Sorry about missing the double L in your name Willcox.

Thanks for the help.

 

Raceman,

The wiper motor ground is shared with the anti theft switch, the heater blower motor and the starter interlock override switch. It is also shared with the delay time and the driver side anti theft removal switch.

If you had wipers with the hood shut it must have been completing the ground circuit for the wire motor. I think at this point I would run a independent ground from the wiper motor to a verified ground source.

The hood being closed and allowing the wiper motor to work makes me think that you have a problem where the ground wires spit off from each other. There is a junction in the wire harness where the main ground, the hood switch, the relay the interlock and all the grounds are connected. When your hood was closed it was completing the ground circuit on the car. There should never be power on this black wire and if there you stand a chance of cooking anything that is in this loop with it.

Running an independent ground to the motor for testing should tell you this is the problem with the car. For you to have power on that ground wire you would have to have something shorted out in the system.

You should run a continuity test on the wires and also check them for a short.

Try this then email me back.

Willcox Inc

 

i hate to say this... and it doesnt exactly fit here... but dont fix what aint broke :P
if bubba had it stuck... its cause somethin was broke and that was his way of fixin it.. im not saying its right, but it makes a small manageable headache a migraine quick like.. Bubba aint right, but work in manageable headaches

 

If the ground wire has 12 volts on it, you are just one defective part from burning up the car!

Yes, the main ground runs to the starter. You can move it to the bellhousing, but you need to find the source of the 12 volts.

To take this out of the loop and see if you can get the wiper motor working on it’s own run a separate ground for the motor.

The source of the power could be any of the components attached to the system. You can start by un-plugging them one at a time to see if the power drops from the wire.

 

The black wire that used to go to the starter,you say shows 12 volts. Have you tried grounding it? You may be showing voltage there because some accessory is on and you are reading voltage comming throuth it "seeking" a ground. If you turn on the key, get a spare fuse and hold it to the engine and then touch the black wire to the other end of it and see if it blows the fuse or if some accessory tries to work. Use maybe a 15 amp fuse and if something starts working, like the fan or wiper motor then go ahead and ground that wire. If not you only wasted 1 fuse to find out.

 

Sorry I could not try any of your suggestions last night. I was busy grouting the tile in my new house. I have been BULIDING my house for the past 15 months and I'm about tired of it so i bought the Corvette so I could just have another project to work on.

But anyways, I will try to address this.

Willcox, the wipers only worked when the hood or door was OPEN not closed. I cleaned all the door micro switches and now nothing works eccept a clicking noise from the wiper motor when I press the wiper switch in. I will run an independent ground tonight to the wiper motor and see if that helps.

Aktbird, I checked the voltage in the ground wire with the key in the on position. I will do what you said tonight and see what happens with the fuse.

Thanks for all your help guys.

Thanks
Aaron

 

Aaron,

I just had it wrong, when the hood is open the switch is making the ground connection complete. This is why it’s cutting off when you open one or the other.

This should not be happening!

There has to be a wire problem between the motor and the ground branch in the harness. Or the wire being hot from something being shorted out is causing back feed voltage to over ride the ground. Make sense?

For what ever reason, there should not be voltage on this wire!

Willcox

 

Ok guys, I think I have it figured out. I grounded out the wiper motor and sure enough it worked. So, like you said Willcox, it was a grounding problem. So, next thing I did was take a 15 amp fuse and ground it out againt the engine and the black wire from the starter with the ignition on. The fuse did not blow. So next thing I did was just grounded out the black wire and switched on the wiper switch and guess what, they worked. So i closed all the doors of the car and pressed down the hood switch with my finger and they still worked. So then I checked for voltage in the black wire with the ingition off. There was none. Then I switched the ignition on and there was none. So I think the reason why I thought there was voltage on that wire was because I must have had the wiper switch on when I tested it before. Therefore it was seeking a ground. So I guess that portion of the car is fixed.
I still have to get the blower motor working. There is no AC on the car at this time and I live in FLorida and i WILL put it back on. Could someone explain to me why my car did not burn down when I had that ground connected to the starter post?

But anyways, thanks everyone for your help. I was so happy I wanted to go drive my car in the rain just so I could see them working.