Wiper's dont work in the rain

[fidelity101]

So this seems like a no brainer, wipers should work when its raining out. Well they work for about 2-3 minutes then just stop all together. They work fine in the dry. I've noticed sometimes I would have to wiggle the electrical connector on the motor and it would start working again (but this was in the dry). Intermittent has never worked but low and high speed do.

Vehicle is 85 suburban for reference, I'm seeing this a common issue on the 93+ vehicles with the printed circuit gone bad or the seal around it goes bad. However on the earlier gen it looks like the wiper motor pulse board module is to blame. Everyone says there cheap part but it looks like the local auto part stores want 100 dollars and even rock auto is about 70.

But this doesn't seem to add up because the board module is located on the steering collum. It shouldn't matter when I wiggle the connector at the wiper motor. Am I missing something here?

 

[Blue85]

The module will affect the delay function. The wipers should still work in regular "on" or "high". It could be you just have corrosion in the connector terminals. It could also be the column switch, but exhaust everything else before tearing into that PITA.

Got a DMM? Measure voltage at the motor connector. Another common problem is the park switch that is located on the motor. You should be able to check that with an ohmmeter or just bypass the switch with a jumper of some kind to see if it makes any difference.

EDIT: does your 85 have the dash mounted switch or the column mounted one?

 

[fidelity101]

The module will affect the delay function. The wipers should still work in regular "on" or "high". It could be you just have corrosion in the connector terminals. It could also be the column switch, but exhaust everything else before tearing into that PITA.

Got a DMM? Measure voltage at the motor connector. Another common problem is the park switch that is located on the motor. You should be able to check that with an ohmmeter or just bypass the switch with a jumper of some kind to see if it makes any difference.

EDIT: does your 85 have the dash mounted switch or the column mounted one?

Yeah I got a DMM. I'm thinking high corossion on the connector as well as it has plauged many other underhood connectors on this vehicle.

It has the column mounted.

 

[Carcinogen]

Check your grounds. If i remember correctly isn't it ground switched?

 

[4xcrazy]

The issue in the 93+ models is loose, broken solder connections on the circuit board in the main module under the hood. I almost went and bought a new one for my mothers truck, then decided to look at it closer. I simply hit the solder joints with a touch of flux and the iron, reheated them, and It's been working fine now for the past several years.

Very easy fix.

 

[fidelity101]

Check your grounds. If i remember correctly isn't it ground switched?

most wipers are ground controlled and the motor is hot at all times or key on. If it was a ground issue why would it only happen when it was raining, it shouldn't work at all then.

I certanitly got some digging to do when I get home today.

 

[Metrodps]

Under the metal cover below the steering column is the delay control module.
It is silver finned and black.
It has two wire harnesses that plug in to it; one on each end.

Unplug each one and then connect them together. This is how regular wipers are hooked up.
Try the Hi and lo wipers positions.

If it works ok you know it is the control module, If not it is the motor.

 

[fidelity101]

Well I took a look at it after work and why my intermittent wipers did not work, thats because the vehicle is not equipped with control module! solved that mystery...

I unplugged the lower connector on the motor and measured 12.Xv, it is hot at all times (key on or off)
then I set the switch to low speed and measured the resistance on the middle pin and got 16.5 ohms
then I set the switch to high speed and measured the resistance on the end pin and got 17 ohms.

I tried with a spray bottle to replicate the concern with water and got water all around the motor and ontop of the motor, the bulkhead and etc and could not replicate my not working while wet. but when I 'forcefully' wiggled that connector I could get it to act up and quit working.

16 ohms seems very high for a ground resistance. There is only 5" of wire coming from the bulkhead to the motor. I looked up the schematic in my haynes but it doesn't show me physically where this ground is on this circuit.

I'm going to take a look at this issue this weekend, grab a second wire harness connector for the motor and try bypassing all the existing wiring and rule the wiring or motor out.

 

[Blue85]

I've always wanted to try putting a relay there with good wiring to see how much faster the wipers go. Even if control switch is old and stock wiring is lame, it would be plenty to pull a relay. It would probably also make the control switch last longer.

On some of these unsealed underhood connectors, you can make stuff work like new again by replacing the terminals. I don't know if you can find new ones or not, but most factory harnesses still reach 1/2" shorter.