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Discussion Starter #1
I thought I had the correct headlight ON/OFF & Dimmer thru RockAuto this week, but what I received isn't matching up. Take a look and see...





If you can get me a P/N I can find thru a reseller that would be great, otherwise I'll I'll make a trip to the junkyard while I got this in pieces today.

Thanks!
 

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I thought I had the correct headlight ON/OFF & Dimmer thru RockAuto this week, but what I received isn't matching up. Take a look and see...

Can you clarify what you want or what is wrong?


The dash switch comes in several forms: 9C1 USA, 9C1 Canada, base model(sedan/wagon) twilight sentinel USA, and twilight sentinel Canada (Daytime driving lights).


The high/low switch looks the same as the one I removed from my Caprice to install the Fleetwood flash to pass version. The only difference is the one you have has a extra piece of metal between the mounting slots. I am unsure what you think is wrong with it.
 

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Very unclear which part you want/need,and/or talking about...
 

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For reference 9C1 dash switch with trunk switch hole instead of change pocket.
Caprice high/low switch.(with shipping/alignment clip)

Mounted Impala high/low (looks like your new part)
 

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Discussion Starter #6
Fellas,
Sorry for the lack of info. I was just getting real hot working outside today, and just posted up before I left for the junkyard.

I'm trying to fix the problem of the dash lights no longer illuminating unless the dimmer switch/interior is on.

I assumed the headlight switch and dimmer were a combination switch assembly like my '98 Tahoe. I was/am now planning on swapping parts/.

I just got back from the junkyard, and got the entire plastic assembly with the headlight switch, dimmer, and trunk switch.

Since I don't need the trunk and have that pocket area of mine already set up with an extra cigarette lighter/12 volt port, I'm going to swap parts over.

I'm not clear at the moment on how to release the headlight switch. There seem to be (4) tits and slotted plastic pieces holding it into the bezel. I can get all (4) tits released but the headlight switch doesn't come out easily.

Am I missing something, do I need to do something other than releasing those (4) catch points?

Thanks!
 

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Discussion Starter #7
Disregard my last post, I figured it out.

I just needed to cool down for a few minutes, and think straight..

I'll post more once I finish up with things today, I appreciate y'all jumping on board with the help.

I wasn't anticipating the quick responses for a Sunday, so that's why I just decided to head out to the junkyard instead of waiting for some replies.

I got myself a headliner, which I'll write about in the 'What did you do....' thread later after I clean up around dinner time.
 

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I assumed the headlight switch and dimmer were a combination switch assembly like my '98 Tahoe. I was/am now planning on swapping parts/.
juniorwatson


Do you know that the instrument lights are controlled by the the "panel lamps dimming module"(power transistor) under the dash?



The dimming control/dome switch sends a signal to the "panel lamps dimming module" The parts you are changing may not be the fix.
 

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Discussion Starter #10
"panel lamps dimming module"(power transistor) Marked in red.
I gotcha, sorry been busy and didn't get to reply right away. I just took a wild stab at things, as I previously wrote, since I had to remove the lower dash section anyway to diagnose a broken parking cable.

I'll head back to the J/Y Saturday and grab that item before they send the car to the crusher, since she's been picked over pretty good.

Thanks!
 

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Discussion Starter #11
Follow-up

I thought I'd follow-up with something I found this morning. I typically don't do much very early morning, or late evening driving these days where I use the headlights, except for when its raining. But today I left a little earlier for work, and it being overcast was a little dark.

I turned on the headlights, and I now have no Instrument/cluster/speedometer illumination whatsoever. I have lighting to my two aftermarket gauges, again with the dimmer rheostat being at its peak position. I couldn't tell if there was lighting in the HVAC section or not.

Would this be a symptom of the transistor section you wrote about? Or is this a typical cluster problem?

I've read about speedometer illumination going in/out, but not the entire cluster. I don't have a 9C1, or the switch to kill the cluster lighting either.

I still plan on going back to the junkyard tomorrow morning, because I checked this morning, and they just got a '96 caprice in stock yesterday.

Hopefully it hasn't been picked to death before even getting to the yard.

Thx.
 

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I have lighting to my two aftermarket gauges, again with the dimmer rheostat being at its peak position.
Would this be a symptom of the transistor section you wrote about? Or is this a typical cluster problem?
I do not have access to my cars at the moment so this is from looking at the FSM and using a meter on the dash dial dimmer.

I think you have a ground problem.

If I have this right the "dash lights" are at their brightest when the knob dot is at it's highest position. When you push it up and the dome light comes on the "dash lights" actually turn off. The dimmer knob resistance(green to )yellow at the high point is Zero Ohms(12 volt to module). But when you turn on the dome this opens(infinite resistance Zero Volts to module). When at the dimmest(bottom) It again puts out Zero volts(green wire)

I think you should check your aftermarket gauge light wiring to make sure it is really grounded. The backwards action is usually the result of a light ground connected to something not grounded. I might bet that the aftermarket gauge lights will also come on when you set the dimming knob to the lowest setting(down).

I turned on the headlights, and I now have no Instrument/cluster/speedometer illumination whatsoever. I couldn't tell if there was lighting in the HVAC section or not.
This could be a bad ground or a broken gray wire. I assume the digital speedometer is not dimming and the factory gauges are not lite.There are three grounds to the cluster but only one for the "dash lights" If the HVAC bulbs are working but do not light chase the gray wire. If they do dim properly chase the cluster and aftermarket gauge light grounds.

I would start by using a test light at the gray wire at the "dimming module" If the test light works you are chasing some open circuits gray wire and ground

I am going to try to explain why the aftermarket gauge lights come on with a different example.

Have you ever been behind a car that has one dim brake light? This can be caused by a bad ground to the bulb. When the bright (brake) filament is powered and has no ground the circuit flows through the park filament then through all the park bulbs in the car to ground. This will dimly light the park filament but not the brake filament. When you turn on the park lights the path changes. The park filament circuit is through the brake filament to the other brake lights to ground. So when the brakes go on both filaments have power but no ground path and the park goes out but the brake does not go on. What I am trying to say is when there is not a proper ground the circuit may have another path to ground and the results are hard to predict.

I hope this makes sense I am short of time today. I think your dimmer knob and control module may be OK and you have a ground issue.

PS If you have a aftermarket radio is the gray wire safely protected if not connected? If you have a factory radio does it dim properly?
 

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Discussion Starter #13
"panel lamps dimming module"(power transistor) Marked in red.
I wanted to follow up my thread since I found the solution to the problem, although it took me a few weeks to finally get the free time.

It was the transistor module that was the root cause. A simple R&R from a junkyard donor fixed everything right.

I appreciate the help!
 

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Junior, happy you got that taken care of. How did the guage deal work?

Mark: Snowman-33
 

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Junior, happy you got that taken care of. How did the guage deal work?

Mark: Snowman-33
That will prob. be this weekend's project (1). I've got a few irons in the fire at the moment right now. I've got to drill the 2 gauge holes in the new cluster cosmetic piece, are re-run the mechanical water temperature sender. Then while I have the dash apart, I'll re-pull the lower dash as well, and tidy up some of the other wiring with nylon wire ties.

2. New transmission temperature gauge install

The other is the interior (3).

1. Headliner refinishing
2. FT & Rear Rocker Panel, Kick Panels, A, B & C Pillar refinishing from gray to SEM flat black, to match carpet and upcoming headliner color.
3. Seat belt refinishing by SSnake-Oyl

4. Install OBD-1 PCM and possibly '95 knock sensors if there is a problem, and start to learn my own programming.

Then onto finishing the '98 Tahoe transmission front assembly rebuild, and new rebuilt engine install & break-in.

All this while trying to house hunt for something $200K or under, and undergo another back procedure on 9/4/18.

I need to play & win the lottery so I won't be so strapped!
 

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That will prob. be this weekend's project (1). I've got a few irons in the fire at the moment right now. I've got to drill the 2 gauge holes in the new cluster cosmetic piece, are re-run the mechanical water temperature sender. Then while I have the dash apart, I'll re-pull the lower dash as well, and tidy up some of the other wiring with nylon wire ties.

2. New transmission temperature gauge install

The other is the interior (3).

1. Headliner refinishing
2. FT & Rear Rocker Panel, Kick Panels, A, B & C Pillar refinishing from gray to SEM flat black, to match carpet and upcoming headliner color.
3. Seat belt refinishing by SSnake-Oyl

4. Install OBD-1 PCM and possibly '95 knock sensors if there is a problem, and start to learn my own programming.

Then onto finishing the '98 Tahoe transmission front assembly rebuild, and new rebuilt engine install & break-in.

All this while trying to house hunt for something $200K or under, and undergo another back procedure on 9/4/18.

I need to play & win the lottery so I won't be so strapped!

Okay. So what do you have planned for the afternoon?
I wasn't going to say anything but WTH. Years ago I went to the casino. I put a $100 bill in. I was over thirty dollars ahead on third spin. Spin # 4 $20,000 jackpot. :grin2: I wasn't there 5 minutes.

Mark: Snowman-33
 
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