I am attempting to upgrade the factory cassette player in my 92 SSEi, but there seems to be a little problem. There is a purple/white wire that comes from the factory deck to the HVAC control head... it'* the "Dim Input" circuit which dims the HVAC display when the lights are turned on. It seems that without the factory deck in place, the HVAC display will stay at it'* brightest setting regardless of how dim you try to make the dash lights. :(

Has anyone out there figured out a way to complete that circuit to the HVAC unit by bypassing the stereo? I have a really sharp Delco CD unit from a 94/95 that I'd like to use, but the later models have a different way of wiring the HVAC display dimmer. Everything else works great with the transplanted unit. I'd imagine anyone who has put an aftermarket head unit in a 92 would have the same problem.

Hoping for a fix!

Dean
92 SSEi

my pioneer doesn't have a dim input signal so i just tied that wire off with no problems.

you should be able to wire it into your dimmer wire directly I would think. I know in my '95 there is a yellow wire that passes through the fuse panel under the dash (where I cut into it and ran a switch up to the dash), and then runs to all the major dimming components (radio, HVAC, Instrument Panel, etc..) If you can find out what color this dimmer wire was on '92'*, and where it passes through the fuse panel by looking in a factory service manual (ask your dealer), then I would try just tying directly into that. It should provide the dimming current to dim the HVAC like it did before going through the radio. Just a thought.

Hey Chris,

You nailed it!

I got my hands on a later model Bonnie wiring diagram and it looks like on the newer ones, the radio and climate control display have separate dimmer feeds to them (the yellow wire you mentioned), whereas the 92 models only have one feed that hits the radio first, passes through it, and then continues on to the climate control display.

I messed around with mine this afternoon and found that the dark green wire (which is the equivalent to the yellow wire in your car) that enters the radio simply passes through the radio and exits the radio as a purple/white wire that goes to the climate control display... so the radio simply acts as a connector to complete the circuit. So I got to thinking... if you remove the radio, and sever the connection, a jumper wire to reconnect the circuit should do the trick. I spliced the purple/white wire and the green one together and that did the trick - it works perfectly!

This would work for anyone installing an aftermarket stereo into a 92 model that has the electronic climate control.

- Dean

Awesome! Glad to hear you got it! Only reason I even thought to get into this was because for safety and looks, I always like to have my parking lights on when driving. I kinda think of them as DRL'* but that look alot sharper Anyways, I noticed when I forst bought the car that I couldnt turn on my parking lights during the day, and still see the HUD which really blew Once I got my factory service manual from Helm about a week after I bought the car, I did some research and rigured out if I put a switch on that yellow dimmer wire right after it comes out of the fuse panel, I could effectively make the whole rest of the car think that the lights really were off Needless to say it works great, been using it for 2 years. Should work on anyone elses too, and I think I have some pics of the wire and the switch on my website.

Glad to hear it worked!!

So how does the dimmer wire work? When power is applied to it it dims the unit it is attached too and when power is cut it goes to full brightness? I am assuming this could be applied to all the units that run off the dim signal (radio, hud, HVAC, etc..). Is there one master wire to tap into or is there going to need to be a switch for each.

I always drive with my parking lights on too (looks bad *** ) but it dims things down too far too see, even when they are as bright as they get under dim. To undim the internal lights while the parking lights are on would be ever so sweet!

Each car has two dimmer circuits...

One uses a gray wire that controls the intensity of all your dash lights, backlit switches, etc. Basically, everything that lights up with an orange color.

The other dimmer circuit varies by year but it looks like most models use a yellow wire. This circuit starts at the fuse block and connects through your headlight switch to all the digital display components - HUD, compass, systems monitor, radio, and elec climate control unit. When you turn on your lights, it sends current to each of those components and dims them. You can further dim them by twisting your headlight switch, but so far there hasn't been a way to keep them at their brightest setting when the headlights or parking lights were on. Until now, that is... use of an on-off switch to disable that circuit is clever!

Sounds like you could either tap into the wire right out of the fuse block which would override the entire system, or you could only single out a certain item - like the HUD - by tapping into the wire right before it gets to the HUD unit. Either way, turn on the switch for everything to work as normal; turn it off and your digital displays will stay at full brightness.

I just might try that for my HUD since it'* so hard to see in the daylight if the lights are on... we get a lot of rainy days up here which require use of lighting way before it gets dark.

- Dean

OK, A while back I swapped the factory cassette stereo in my 93 SSEi with a stock CD player from a 2001 Trans-Am. The wiring harnesses were different, but I modified the existing wiring to work with the new stereo. I did this because the CD players with the green vf display were only made for 2 years (92, 93) and are too hard to find.

I found the correct pin on the back of the Trans-Am stereo for the steering wheel controls. Those work fine.

But I could not get the dimming capability of the vf (green) display of the climate control back. This may only be a problem that plagues 93 (and maybe 92) SSE/SSEi.

The service manual shows the purple and white wire from the radio to the climate control as a special signal produced by the radio only! It appears to be some sort of an oscillating signal that dimms the climate control VF display. When you apply 12V to the purple and white wire, the display goes blank! It'* not like your standard dimming signal (0-12V for incadescent lamps). I tried the earlier suggestion in this thread about splicing the purple/white and green wires together, but it didn't work.

So get this... I bought an old junk 92 sse radio, put it in the trunk, and wired back to the trunk... just so I could have the climate control vf dimmer. That worked, but it was way too much effort. And now I have a radio in the trunk too!

Has anyone messed with this any further? I only think this problem plagues the 93 (and maybe 92) SSEi, because the radio was switched (upgraded) to the red digital display in 94.

Hey fuddyduddy121 -

I had totally forgotten about this topic being here... Glad you kicked it back up to the top.

Turns out the splicing of the wires did not fix the HVAC display issue for me either... so I've been working on the issue on and off for the last couple months. Here'* what I've found so far:

This "issue" only affects 92 and 93 Bonnevilles with the digital HVAC display/controls. The HVAC VF dimmer only works properly when fed through the radio first. Direct wiring won't work... the display goes black. Not hooking up the wire at all causes the display to be at full brightness (which is the way mine is right now).

I thought about stashing the original 92 stereo in the trunk, too, but thought of another approach that I'm going to try. We know that you can install a later model stereo into the 92-93 models successfully, as you and I have both done so, but the problem lies with the HVAC display. I got to thinking... the 94 Bonnie has the newer style stereo, but has the same (or at least similar) HVAC display as the 92-93s, so they must have changed the VF dim circuit wiring in 94. The 95+ cars had a major makeover with the HVAC system, so I know those aren't even close to ours.

So I hit the library and started digging through wiring diagrams, and sure enough! The HVAC display from a 94 -should- work in a 92-93, provided you swap the wires at pins 4 and 5 (Data Link Circuit) and wire in the VF dim circuit directly instead of having it feed through the stereo first. All the other pins on the 94 match the 92-93 units.

I am going to pick up a 94 HVAC display as soon as I can find a cheap one to test my theory. Will let you know how it goes, and if it works, will provide the wiring changes necessary to do it.

BTW - What kind of mods did you make to your 2001 stereo to get it to fit into the dash opening? Mine lines up good on the right side, but the holes and alignment pin don't line up on the left.

Dean
92 SSEi

If that HVAC swap works for the stereo upgrade dimmer problem, PM or Email me the procedure so I can add it to the Techinfo section. The fact that at least 2 of you ran into this warrants documenting it for posterity.