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Old 08-04-2004, 11:33 AM   #1
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Default Dash Lights Relay

I believe my wife'* 93 SSE has a bad relay for the dash lights. As you know, when the photocell detects low light conditions, the headlights will come on and the dash lights will dim. This works fine on her car, but after a period of time I'll hear a relay click, the dash lights will flare (brighten) for a fraction of a second, then all will be normal. Nothing else is affected and it only happens at night, when the headlights are on. So I figger I gots me a weak relay. $7 later I have a new relay and locate the relay panel under the passenger side of the dash, where I discover no less than 8 stinkin' relays!

My question is, which relay controls the dash lights? They appear to be stacked in 2 vertical columns of 4 relays, like this:
[1][2]
[3][4]
[5][6]
[7][8]

with relays [1] & [2] being at the top. I made up the numbering scheme so anyone who happens to know the location of which relay I seek can identify it by number.

And, if anyone'* ever nosed around these relays, any hints on the best way to access them would be much appreciated. There doesn't appear to be a whole lot of room in there - looks like I'm in for a real adventure if I have to change any of the top relays!

SM
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Old 08-04-2004, 11:52 AM   #2
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this is from my '89 shop manual, so it may vary, but it should be the same, maybe someone with your year shop manual can confirm this.

1)Fuel pump and oil light relay [opt]
2)Bose Radio Relay [OPT UQ4]
3)Horn Relay
4)Rear Defog Relay [OPT C49-C68
5)Fuel Pump Relay
6)A/C Select Relay
7)Auto Level Control Relay [OPT Y98]
Fog Lamp Relay
9)Door Lock Relay

the order for this goes as followed:
1 -top left
2 -2nd last left
3 -top right
4 -3rd left
5 -2nd right
6 -4th left
7 -3rd right
8 -bottom left
9 -bottom right


-justin
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Old 08-04-2004, 02:58 PM   #3
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Hmm. None of those say anything about the dash lights. The relay locator sheet I looked at said the relay I'm looking for is under the dash on the passenger side, but it wasn't any more specific than that. Maybe there'* more relays under there that I didn't see.

Anyone got a '93 shop manual they can look at and tell me exactly where the dash light relay is?
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Old 08-04-2004, 03:11 PM   #4
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Default Re: Dash Lights Relay

Quote:
Originally Posted by SSE Motorhead
I believe my wife'* 93 SSE has a bad relay for the dash lights. As you know, when the photocell detects low light conditions, the headlights will come on and the dash lights will dim. This works fine on her car, but after a period of time I'll hear a relay click, the dash lights will flare (brighten) for a fraction of a second, then all will be normal. Nothing else is affected and it only happens at night, when the headlights are on. So I figger I gots me a weak relay. $7 later I have a new relay and locate the relay panel under the passenger side of the dash, where I discover no less than 8 stinkin' relays!
Hmmm... where to start here...

Your dash backlighting doesn't have a relay of its own; what I assume you're referring to here is the Twilight Sentinel controller. What _may_ be happening, if I'm understanding your description right, is that the entire controller is temporarily switching the vehicle lights off, such as if you spend too much time under a strong streetlight or lighted canopy. The controller has a large relay built into it, but it resides on the multi-function bracket under the driver'* side of the dash, I think attached to the bracket that holds the hinge for the swing-down fusebox. When you hear the lighting relay click, I think you should notice that its sound is coming from somewhere just behind the headlight switch, not from the relay bank on the passenger'* side (which is not involved).

I'm not sure what sort of relay you bought (are you talking about a generic 30-amp Radio Shack relay?) but unless you left out a lot more detail about it, I have a feeling it'* not going to be the exact replacement for the existing Sentinel relay, nor the cure for this problem.

I would start by pulling and reinstalling the Twilight Sentinel controller, as well as the light sensor in the dash above it (it'* the little flush-mounted button on the top of the dash adjacent to the VIN plate), and see if oxidized connections might be the problem here. Bonneville dashes in general develop this problem over the years, and my Twilight Sentinel is a little flaky, too (becomes hypersensitive to light, to the point that the car will turn its light off while I'm driving along), so I pull the headlight **** out manually to be sure that I don't get surprise darkness while driving.

One of these days I'll pull my controller out and see if I can get the Sentinel working properly again. Let us know if you find out anything further about yours.
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Old 08-04-2004, 03:26 PM   #5
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Relay center positions:

A-K
B-J
C-H
D-G
E-F

A-Unused
B-LH front door isolation (RPO AU0 only)
C-Rear defogger (SSE & SSEi) Fog lamp cut-out (SE)
D-Trunk release (RPO AU0 only)
E-Retained accessory power #1(RPO KP2 only)
F-Interior lamps (RPO C97 only)
G-Fog lamp
H-Fuel pump
J-Retained accessory power #2(RPO KP2 only)
H-Unused

There is no position I for some reason. The auto headlights are controlled by the Lamp Control Module and not a separate relay. Also, there is not a relay that runs the instrument cluster backlighting
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Old 08-04-2004, 05:51 PM   #6
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Quote:
Originally Posted by randman1
The auto headlights are controlled by the Lamp Control Module and not a separate relay. Also, there is not a relay that runs the instrument cluster backlighting
What he said. The only audible relay (i.e. one that you can hear clicking inside the car) that'* involved in vehicle lighting is the one controlled by the Twilight Sentinel, which bypasses the standard headlight switch on the dash. (I can't remember offhand whether there are relays for high- or low-beam use in the MaxiFuse/Relay Center on the firewall under the hood; someone else can probably tell us.)

So if you pull out the headlight **** to turn on the car lights, you won't hear a click; if you let the Twilight Sentinel turn on the car lights, you will hear a click.
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Old 08-04-2004, 06:32 PM   #7
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I will have to look into this a little further. The only thing affected is the brightness of the dash lights (like the DIC, the radio display, etc.). For night driving these lights are dimmed. When the problem occurs, these lights will momentarily brighten - almost flash at me. The headlights do NOT dim, at least not that I can detect. For this reason I don't think the photocell is the problem. It'* more like a relay is weak and drops out and the lights brighten, but the photocell says "it'* night!" and pulls the relay back up, dimming the lights again.

According to a relay listing I looked at, there'* supposed to be a relay that controls these lights. Could very well be that this listing is wrong. I'll check it out this evening.
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Old 08-04-2004, 06:43 PM   #8
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The reason there is no position "I" is because I can be mistaken for a 1. "O'*" are also typically omitted in electrical connectors and schematics to aviod confusion with zero.

Next time you get that question in Trivial Pursuit you can impress everyone in the room with the answer!
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Old 08-04-2004, 06:55 PM   #9
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Quote:
Originally Posted by SSE Motorhead
I will have to look into this a little further. The only thing affected is the brightness of the dash lights (like the DIC, the radio display, etc.). For night driving these lights are dimmed. When the problem occurs, these lights will momentarily brighten - almost flash at me.
Okay, is it only the fluorescent displays that are malfunctioning? That is, does the red backlighting of the gauges go dark at the same time?

Quote:
The headlights do NOT dim, at least not that I can detect. For this reason I don't think the photocell is the problem. It'* more like a relay is weak and drops out and the lights brighten, but the photocell says "it'* night!" and pulls the relay back up, dimming the lights again.
If you're not hearing a click when this is occurring, it'* not a relay issue. If you _do_ hear clicking, then your headlights may well be going out occasionally, since the Twilight Sentinel relay controls them as well as all the other lights.

All that aside, unless you're actually hearing a relay noise, I'm thinking this is more of a problem with the fluorescent display dimming circuits. They're supposed to monitor backlighting levels (i.e. the dash backlighting current in the gray wires behind the dash)and dim themselves appropriately, but if they don't detect current in the backlighting circuit, they'll use their full-brightness setting instead.

Quote:
According to a relay listing I looked at, there'* supposed to be a relay that controls these lights. Could very well be that this listing is wrong. I'll check it out this evening.
Okay. Where did you find that listing?
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Old 08-04-2004, 08:52 PM   #10
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I don't understand the problem. Are the green displays simply momentarily going bright and then back to their normal dim? And you are hearing a click when this happens? What is going on with the red lighting and your headlamps?
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