"thunk" Sound From Rear When Turning On Foglights On '01

[Starrman]

Anyone else notice this? About half the time when I switch on my foglights I hear a thunk sound coming from the rear of the vehicle. It almost sounds like the rear window wiper going back into its holder when switched off...something like that.

[pwall]

There is a problem with the switch in the dash.

When you power-on your fog lights, what you are hearing in the back is the rear wiper blade getting power but only for a split seond. Hence the noise.

 

Replace the switch.

[C & A s Dad]

Man, that Pwall knows some stuff doesn't he?

[Bish]

I had the same issue on my 01 Tahoe. I did some TSB for a ground problem somewhere in the rear of the vehicle. I decided it wasn't worth the effort and just ignored it. Vehicle was fine up to 205K when I traded her in and the switch and wiper still operated fine. I had not heard of the switch being the problem.

[Starrman]

How hard would it be to replace the switch? Can it be gotten from under the dash or would the front have to come off somehow? Is it just a foglight switch or is it clustered with the headlight and dimmer controls?

[pwall]

Actually, now that I think of it....it could have been a grounding problem in the back.

I'll see if I can find the work-order from the dealership when I had that issue addressed several years ago.

 

Of course if the 'noise' doesn't bother you, you can always leave it. It's more of an annoyance than anything else.

[pwall]

Man, that Pwall knows some stuff doesn't he?

You're making me blush....

[pwall]

Ok, me again....I actually found the work order from the Dealership, dates back to June 6, 2004.

Here is what it says:

 

"COMPLAINT: WHEN TURNING ON FOG LAMP, READ WIPER ARM JUMPS T.S.B.

CAUSE: (93) READ WIPER JUMPS WHEN FOG LAMPS TURNED ON.

#03-03-43-001A

CORRECTION: REMOVED READ WASHER PUMP GROUND WIRE INSTALLED NEW GROUND

AS PER BULLETIN, ALL O.K. NOW. "

 

Hope that helps! ;)

[Starrman]

Ok, thanks. I guess that would be the main washer pump in the engine compartment? Or is there a smaller one just for the rear somewhere?

[alvocado]

Does anyone have the full TSB details for this: 02-08-43-001A MAR 04 Wipers - Rear Wiper Jumps When Turning Fog Lamps ON. It would be good to post it in the tech wiki.

[bull516]

Does anyone have the full TSB details for this: 02-08-43-001A MAR 04 Wipers - Rear Wiper Jumps When Turning Fog Lamps ON. It would be good to post it in the tech wiki.

I did the work, per the TSB, but it did not solve my problem. I initially had the same thunk issue, but mine got worse about a month ago. Now, when I turn on my fogs, the rear wiper will turn on, and continue to operate until I turn the fogs off. Not only does it fully run, the intermittent function doesnt work. When the fogs are on, and I try to turn the wiper switch, nothing happens. This is weird??? I have yet to find any one having this latest issue.

So what I have done (temp fix) is to disconnect the ground from the rear washer pump harness. Now, the fogs work, the wiper works, but the washer pump is disabled. Not a big loss since i rarely used the washer anyways. I was more concerned with being able to use the wiper, especially in snow storms.

[Starrman]

where is the rear washer pump (and the ground for it) located?

[bull516]

where is the rear washer pump (and the ground for it) located?

Ok, this is tricky. The pump is located (on my Denali) at the base of the main washer fluid Reservoir in front of the battery. Getting to it is the tricky part. The TSB called for removing the fender, the wheel well cover, and the battery. This makes getting to the pump very easy. I did not have the time to do the steps given, so i just removed the wheel well cover, jacked the truck up, removed the bolt securing the reservoir to the body. From underneath the truck, you can see the pump at the base of the reservoir. Then I managed to squeeze my hand into the tight space to unclip the harness for the rear pump. Its very, very, very tight, but do-able. I also removed my drivers headlight and turn signal assembly. Doing this gives you another way to access the pump. This was actually great when it came to reconnect the harness. Once I removed the harness, I just cut the ground off the harness, and extended the ground to the chasis. Unfortunately, this new ground didn't solve my big problem with the crazy wiper action, but it did solve the thunk heard when turning the fogs on. Since I need the wiper more than the washer function, I just left the ground untapped. By the way, this is a new fog/wiper switch, so my problem is not the switch.

[hubbycap]

where is the rear washer pump (and the ground for it) located?

Ok, this is tricky. The pump is located (on my Denali) at the base of the main washer fluid Reservoir in front of the battery. Getting to it is the tricky part. The TSB called for removing the fender, the wheel well cover, and the battery. This makes getting to the pump very easy. I did not have the time to do the steps given, so i just removed the wheel well cover, jacked the truck up, removed the bolt securing the reservoir to the body. From underneath the truck, you can see the pump at the base of the reservoir. Then I managed to squeeze my hand into the tight space to unclip the harness for the rear pump. Its very, very, very tight, but do-able. I also removed my drivers headlight and turn signal assembly. Doing this gives you another way to access the pump. This was actually great when it came to reconnect the harness. Once I removed the harness, I just cut the ground off the harness, and extended the ground to the chasis. Unfortunately, this new ground didn't solve my big problem with the crazy wiper action, but it did solve the thunk heard when turning the fogs on. Since I need the wiper more than the washer function, I just left the ground untapped. By the way, this is a new fog/wiper switch, so my problem is not the switch.

 

 

 

MAYIN! I think mine would keep thunkin'.