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goodwrench9124
goodwrench9124, ASE Certified Technician
Category: Chevy
Satisfied Customers: 3420
Experience:  Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
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Chevrolet Tahoe I have a 2004 Chevy Tahoe and the rear wiper

Customer Question

I have a 2004 Chevy Tahoe and the rear wiper stopped working. I took the panels off and looked at the motor. I can hear a clicking sound and assumed the motor was bad. When I tried the new motor, it didn't work either, but there was no clicking sound. I then proceeded to change the rear window fuse, still nothing. I have been reading online that this may be a grounding issue since the clicking sound can be hear even when the ignition is turned off. Luckily I was able to return the new motor since the motor may still be good. I'm looking for advice on how to diagnose if its a ground or electrical issue and how to resolve.

thanks,

Howard
Submitted: 3 years ago.
Category: Chevy
Expert:  goodwrench9124 replied 3 years ago.
Hello and welcome. when you installed the new motor, did you have the liftgate or glass open when you tried to see if the new motor worked?
Customer: replied 3 years ago.
Yes, was at the auto parts store and had the liftgate up, plugged the new motor in,did not close the door during the test.
Expert:  goodwrench9124 replied 3 years ago.

Ok, then the motor may have ben your problem. the liftgate has detent switches in it, these detent switches is the ground for the rear wiper motor. in other words, the wiper motor is disabled with the liftgate open.

 

The liftgate ajar switch signal circuit provides information to the rear window wiper module about the status of the liftgate. If the liftgate or liftglass is open the rear wiper operation is not performed

 

if you have a test light or voltmeter, I can give you a few tests to make just to make sure the motor is bad or good?

Customer: replied 3 years ago.

Ok, I can go back and try the new motor with the tailgate closed. How do I use a volt meter to test if the motor is good? Specifically, where are the positive and negative contact points I should use on the test? I'm not good at electrical issues so I will need some extra detail here.

 

thanks,

 

Howard

Expert:  goodwrench9124 replied 3 years ago.
ok, pretty basic tests. voltmeter on 12 volts scale, take black lead of meter to a good chassis ground, take red lead touch orange wire to rear wiper motor connector. should have 12 volts all the time, next take red lead from meter and touch gray wire, should have 12 volts with wiper switch on, if these voltage checks ok, 99 percent the motor is bad. the only way to check the ground circuit is thru the bcm connector, the liftgate ajar swiches provide the ground for the rear wiper thru the bcm
Customer: replied 3 years ago.

Hi,

 

I just went back to the store and tried the new motor with the door closed, it didn't work, but I heard the same clicking sound as the old motor so I'm assuming that both motors are ok. I don't have a volt meter so will have to go buy one and test what you mentioned above. However, assuming that the motors are good, any advice on what I else I should look for in the electrical system? You mentioned the bcm connector, where and what is that and how do I test? Thanks in advance for your help.

 

thanks,

 

Howard

Expert:  goodwrench9124 replied 3 years ago.

Ok, don't worry about the bcm, it only receives a message from the liftgate ajar switches, so it will know if the liftgate is open or closed, it wont alter the wiper operation. however if you had a high end scan tool you could check the ajar switches which supply the ground for the rear wiper.

 

basically if the power check ok, then it would be a ground problem.

 

lets back a bit and make sure the easy is ok, there are two fuses for the rear wiper, there is a 25 amp fuse in the under hood fuse blocked marked RR WPR make sure this fuse is good. the second fuse is in the ip fuse block on the left side of dash, this fuse is a 15 amp blue fused also marked RR WPR. if both these fuses are good, then we can make the voltage checks at the wiper motor.

 

here is a brief description on the system works.

 

 

The rear wiper/washer system consists of the following components:

Rear wiper/washer switch
Window wiper module-rear
Window washer pump-rear
RR WIPER 15A fuse
RR WPRB 25A fuse

Rear Wiper/Washer System Operation

The rear wiper module controls rear wiper motor operation. Battery voltage supplied to the module is used to operate the wiper motor in all modes and to return the rear wiper arm to the park position after the ignition is turned off. Accessory voltage supplied to the rear wiper/washer switch is used to supply the rear window wiper and washer switch signal circuits. In wiper switch positions 1 and 2 the wiper switch signal circuit voltage level to the wiper motor module determines the wiper motor delay interval. The rear window washer pump supply voltage circuit is used to provide the operating voltage for the rear washer pump for as long as the rear washer switch is pressed. The rear window washer switch signal circuit is used as a wash signal to the rear wiper motor module to operate the wipers during the rear wash operation.

The liftgate ajar switch signal circuit provides information to the rear window wiper module about the status of the liftgate. If the liftgate or liftglass is open the rear wiper operation is not performed.

goodwrench9124, ASE Certified Technician
Category: Chevy
Satisfied Customers: 3420
Experience: Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
goodwrench9124 and 10 other Chevy Specialists are ready to help you
Customer: replied 3 years ago.

Ok, thanks for all the information, you have been great. I checked the fuse in the side of the dash, but will check the one under the hood. I also ordered a replacement wiper switch hoping is just may be a bad switch since I heard the motor clicking sound even when the ignition is off.

 

I want to also ask if this is connected to my rear defogger not working or if it's a separate issue, but want don't want to get your advice without paying. Is there a way I can send another $15.00 to you so that you can reply and that I can try the fuse and switch and get back to you?

 

thanks,

 

Howard

Expert:  goodwrench9124 replied 3 years ago.
You are very welcome, The rear defogger probably is not related, can you give me a little more info, does the switch light up at all? are all the rear grids inop? as far as paying, we want you to be happy with our help! if you are happy with my help with the wiper problem, and if I am helpful with the rear defogger issue, then you can just simply accept both answers on this thread!!!
Customer: replied 3 years ago.
The switch light lights up, the wires are connected on back glass and all of the rear grids are not working. The other morning when it was cold and the rear window was fogged over, typically I can see the defrosting happening along each of the grid lines.
Expert:  goodwrench9124 replied 3 years ago.
Ok, lets start with the fuses, there are two fuses for the rear defogger, both in the under under fuse block. first fuse is a 30 amp fuse marked RR DEFOG, the second fuse is a 10 amp fuse marked SEO IGN. check these fuses and let me know if they are good?
Customer: replied 3 years ago.
I checked all the fuses and they are good.
Expert:  goodwrench9124 replied 3 years ago.

Ok, good. I suspect a bad relay. this rear defogger is a tough one. the Body control module does control the rear defogger. since both fuses are good, and you already verified that the both connectors are attached to the rear glass. the rear defogger relay is in the ip fuse block, there is normally another relay for another circuit you can swap with just for testing purposes. try swapping relays. if there isn't a relay in the ip fuse block the same, look in the underhood fuse block.

 

Here is how the rear defogger works

 

When you turn the ignition to the ON position, ignition voltage is supplied to the DEFOG relay coil. Battery positive voltage is supplied at all times to the DEFOG relay switched input. When the rear window defogger switch is depressed, the HVAC control module illuminates the rear window defogger indicator and sends a class 2 message to the BCM. The BCM energizes the DEFOG relay by grounding the control circuit of the relay. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger. Ground for the rear window defogger is provided by G306. If the vehicle is equipped with cargo doors, ground for the rear window defoggers will be provided by G410.

goodwrench9124, ASE Certified Technician
Category: Chevy
Satisfied Customers: 3420
Experience: Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
goodwrench9124 and 10 other Chevy Specialists are ready to help you
Customer: replied 3 years ago.
Ok, I was able to get a replacement wiper switch and this fixed the rear wiper issue so this issue is done. As for the rear window defogger, I was able to get a replacement relay from Chevrolet and installed it, but have not been able to check if it works fully, will let you know.
Expert:  goodwrench9124 replied 3 years ago.
Ok, good deal. let ma know how you come out with the rear defogger
Customer: replied 3 years ago.

Ok, been real busy with work so haven't been able to work on the truck. A couple of things:

 

1) The wiper stopped working again and I've been reading a lot of forums online about this issue. Most people replaced the motor and or switch and still did not solve the problem. However, after adding a ground wire from the motor to the car body solved the problem. Any advice on literally how I should add the ground wire? Is it simply just connecting a wire from the motor to any metal part in the tail gate?

 

2) Regarding the rear window defogger, this still does not work after replacing the relay. The defroster button does still light up when pushed and sometimes I can hear a "click" sound when I push the button like it's turned on.

 

thanks,

 

howard

Expert:  goodwrench9124 replied 3 years ago.

as far as adding a ground, you will need to run a wire from the connector of the motor using pink/black wire which is at terminal a of the connector, to anything metal on the tailgate.

 

on the rear defogger, check for battery voltage at the purple wire on the rear glass with the defogger turned on, let me know what you get?

Customer: replied 3 years ago.

Ok, I took the back gate panels off and have some questions:

 

1) Regarding the wiper, I see the pink/black wire that is one of five that go into a connector that attaches to the wiper motor. When you say run a wire from the connector, do you mean that I should take the wires out of the connector and add a wire to the pink/black wire? Or should I just cut the pink/black wire and then add the ground wire prior with a twist cap?

 

2) For the rear defogger, I bought a volt meter, but I am not good at electrical issues. I looked at the rear glass and don't see a pink wire. I only see the black wires attached on either side into the connectors that go into the glass grid. Should I be looking somewhere else? Also, literally what should I touch the black and red volt meter wires to to get the battery voltage?

 

thanks,

 

Howard

Customer: replied 3 years ago.

Here's some additional information:

 

When the key is off I can hear a clicking sound from the motor. In addition, if the key is off and the wiper switch is left on "2", then I can hear the clicking and every 20 seconds or so the dash board lights flash off and on. I just disconnected the wires from the motor to eliminate the clicking.

Expert:  goodwrench9124 replied 3 years ago.

oK, on the wiper, just runs a ground from the pink/black wire, just cut the wire at connector and splice together.

yes check at the rear black wires at rear glass. set voltmeter to 12 volts scale, on most meters it will be a 20 volt setting. take the black wire from meter and touch to a ground {something metal}, the red lead to each black wire

 

 

Customer: replied 3 years ago.

Ok, I tried a couple of things:

 

1) Rear Wiper Motor

I tried ground the wire from the black/pink wire and a couple of different things happen. The first is that if attach the ground wire to metal on the back door, the vehicle thinks the rear door is open. I'm guessing that the ground wire shorts out the door locking mechanism somehow. Where can I run the ground wire to? Does it have to run to somewhere outside of the back door on the car body? Also, now when the ground is not attached the wiper seems to work, but this happened last time and stopped working shortly thereafter.

 

2) Rear defogger

From the inside, it get a volt reading between 10.4 and 11.5 volts from the left hand wire. The volt measurement fluctuates and sometimes I don't get any volt reading. For the right hand wire I don't get any volt reading.

 

thanks,

 

Howard

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