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Ever since I bought my 1985 Trans Am, the dash lights have been very dim. In addition, the door chime is barely audible. Could this be due to a failing remote dimmer? The illumination is so low at night that I can't read the trip meter. This past weekend I took the instrument cluster out to check bulbs. All were fine. If it is the remote dimmer, do any of you have tips or tricks on getting it out? I have been down in the driver's footwell on my head. I removed the hush panel but do I also need to remove the lower panel on the dash? There has got to be some trick to getting that thing out. By the way, I thought it was my headlight switch and dimmer on the instrument panel, but I've already swapped that out with no results.
Its been awhile since I did mine, but as I recall you do need to remove the lower dash panel, it is buried and a pain in the pain in the *****. It is one of those, you can work on or see it, but you can't do both.
Now that you've told me how much fun you had getting to it(high sarcasm), tell me how you did it? I saw those photos on Google. It is so difficult to see this thing that you can't even see it in the pic. It just points to where it is located.
My other concern is whether to go through all the hassle. I do have illumination and can read everything OK. It would be nice to control the brightness but I've lived with it this way for some time.
I was finally able to pull this darn part out! Just as everyone has said, it is near impossible to see. I really had no idea where it was until I had rummaged around in a salvage yard car and spotted it. So then I knew where it was. Two 7mm bolts hold it in. After that, I was able to pull it down and remove the harness connector. And yes, I had to take off all the lower panels to get to it.
I replaced the NTE98 transistor on the heat sink. After restoring everything and reconnecting the battery, the problem remains the same; very dim dash lights and no control with the dimmer dial. Anybody have any idea what this problem could be?
the door chime is barely audible. Could this be due to a failing remote dimmer?
The Remote Dimmer has nothing to do with the Chimes.
Using a voltmeter or test light (the type for testing for voltage, not a continuity tester) probe the dark green wire with the WHITE stripe going to the dimmer wheel.
When you rotate the wheel back and forth — what happens on the meter or test light?
Then probe the brown wire.
When you rotate the wheel back and forth — what happens on the meter or test light?
Then probe the probe the plain dark green wire .
When you rotate the wheel back and forth — what happens on the meter or test light?
Poor results?
Use an OC28 transistor to replace the NTE98.
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I will definitely wring out those wires and see what I get. I assume I'm looking for a change in DC voltage, correct? Per the FSM schematic, it would seem that the brown wire is providing power to the headlight switch/dimmer dial. The dark green and white is the output of that signal from the dial/rheostat to the transistor. Finally, the dark green wire is the signal after it leaves the transistor.
I don't have any previous experience with Thirdgen Firebirds, so I don't know if this is a common problem. After installing a replacement transistor, the dash lights were slightly brighter, but still no control.
I pulled the headlight switch and the associated harness connector for the dimmer. What I found surprised me. There is electrical tape around what appears to be a splice of the black with the brown wire. Looking at my FSM, this would seem to bypass the dimmer function altogether. I am trying to wrap my head around why this would be done?
And how do I correct the issue? There is already a black wire in the harness connector. Where did this other black wire come from? Any thoughts or suggestions are welcomed.
Last edited by gearhead141; 02-16-2016 at 02:45 PM.
Reason: Update
A little more poking around and I discovered that the black wire is the ground from the switch light. That's the tiny little light in the switch. Anyway, that ground is connected to the instrument panel just left of the steering column. The spot is identified as "G200" in the FSM. I'm going to have to crawl under there and see if I can find the other end and restore it. Perhaps my chimes are barely audible due to the ground issue?
One of the theories I have as to why this might have been done is that the PO had a scanner installed where the radio used to be. The harness was completely hacked up, as if it was just cut off. I restored all of that. Maybe it caused a short and blew the rheostat for the dimmer? I feel that I'm getting close to solving this problem!
Problem solved! At least to some degree. What I found was that a jumper had been installed from the gray power lead of the switch light to the brown lead of the rheostat. This effectively bypassed the rheostat altogether. When I turned on the lights, I was getting full illumination. To me, it didn't seem to be that bright.
So now, with the circuit restored, the dimmer wheel has to be turned full bright to get near to what I had before. I need to get better illumination than that for my 58 year old eyes. Would the transistor Nina mentioned in a previous post be the answer? And if so, where do I get one of those? I was able to get a replacement NTE98 at Fry's Electronics locally. Is there an NTE number that corresponds to the OC28?
I did a cross reference to "OC28" to an NTE number and came up with an NTE104. I purchased one, installed it, and got no dash lights at all. Moving the dimmer wheel had no effect. I removed the cluster and checked all the bulbs. I found that they were all 194 part number and in good condition. So now I am back to the original NTE98 remote dimmer transistor. Still the dash lights are barely adequate. I am able to drive at night, but don't have enough illumination to read the trip meter. Am I missing something here? It would seem that if I could turn the rheostat a little more, I would be able to see everything clearly. This can't be the way it is supposed to be.
I think I would have plenty of light if I could just figure out what's drawing the current down. I thought that it might be the chime module drawing added current, but I pulled it out and noticed no difference.
……the dimmer wheel needs to be turned full bright to see anything. So, I'm left pondering whether to install high intensity bulbs…… What will the other transistor do differently from what is now installed?
Yes higher intensity bulbs will help, and if the brightness is like you want then you won’t need to replace the NTE.
The other transistors I listed are “low power” ones.
The NTE is too much as it is a high power unit with too high thresholds.
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You gave me quite a list there Nina! I tend to agree with you that the transistor is the bottleneck in the circuit. Was this a common problem in the thirdgen Firebirds? From what I can gather, the remote dimmer first came out on the 1985 model. So, I can't be the only one dealing with this. Which transistor would you recommend? I could use half again as much brightness, and I know those 194 bulbs can handle it.
I'm getting pretty good at swapping out transistors on that heat sink, for whatever that is worth!
I want to wrap this up and give my results. I removed my instrument cluster one more time to replace bulbs. I installed 168 minibulbs in all the sockets(11). After putting everything back together, I noticed the instruments were brighter. So the bulbs helped quite a bit. I'm still not happy that I have to have the dimmer wheel at full bright, but I will live with it. The original powered transistor is back in the remote dimmer. There wasn't much difference between the new one and the old. I can't understand why GM used that particular transistor. There is nothing for cluster lights until the dimmer wheel is at least at half of its travel. Sure, I could have gone with LEDs but I feel the system should work properly as designed. Yes, I realize I'm dealing with 30+ year car, and new technology is supposed to be better. At the tender age of 58, I prefer to think I'm Old School. Let's just leave it at that. For those of you who want a few photos of what you are looking for, here you go:
1. The first photo is of a new in-box powered transistor bought at Fry's Electronics for $18.99
2. Second photo is the original NTE transistor.
3. Third photo is what the remote dimmer looks like out of the car. Those two 7mm bolts are what mount it.
4. Fourth photo is the other side of said transistor. Remove those two bolts and the assembly comes apart. The transistor is merely pushed in and easily replaced.
Last edited by gearhead141; 03-14-2016 at 11:43 AM.
11-24-2015, 12:47 PM
