'85 Instrument Cluster
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
'85 Instrument Cluster
My never ending digital cluster saga continues... I had my cluster repaired locally. It worked fine. It's out of warranty. The "back-light" lights (all 4) quit working. :smash: At first, they would go out for an instant and come back on. Then, each time they did that they were out for longer and longer. The instrument fuse is good. All the other lights associated w/that fuse light. I can barely see the gages in the daytime and they all work correctly. At night I need a flashlight to see them... :cry I've already removed the cluster and cleaned all the connectors. I've shined a bright light directly at the photo cell and there was no difference in illumination.
Any ideas? I may be able to get the local guy to fix it for me but I don't want to pay the flat rate for repair again as the dash works.
Thanks!
[Modified by Jim Strathearn, 12:20 PM 1/19/2004]
Any ideas? I may be able to get the local guy to fix it for me but I don't want to pay the flat rate for repair again as the dash works.
Thanks!
[Modified by Jim Strathearn, 12:20 PM 1/19/2004]
Instructor
Joined: Jun 2003
Posts: 200
Likes: 0
From: Tempe AZ
Re: '85 Instrument Cluster (Jim Strathearn)
as far as fixing it, I dunno but I've seen previous threads on how to do it. a search might pick it up. if you find an easy way, lemme know cause I got one backlight out. tough to see my oil pressure and the top of the bar graph on the speedo...
Drifting
Joined: Jan 2001
Posts: 1,970
Likes: 21
From: Denville NJ
Re: '85 Instrument Cluster (Jim Strathearn)
Are you talking about the four bulbs behind the metal tabs in front of the cluster? If so, those bulbs are replaced from the front using very thin needle nose plies. If the bulb sockets are bad, then the cluster has to come out and the sockets twist out and new ones can then be installed. Don't try to remove the sockets from the front, I did and it fell into the cluster so I had to take the cluster apart anyway. Try replacing the bulbs first and don't forget not to touch them with your bare fingers. Body oil causes them to burn out prematurely. I use double sided tape and needle nose pliers. Just grab the bulb and pull it straight out. Hope this helps.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: '85 Instrument Cluster (Jim Strathearn)
There is a single row of pins on the forward circuit board that plugs into a socket on the rear board (as the driver sees them). The pin closest to the center of the board carries the current to the 4 lamps and the sockets' spring becomes age relaxed increasing the connection resistance. The lamp current through this resistance makes heat which weakens the spring some more until it gets so hot that it unsolders the pin on the front board which shuts the lamps off. Resoldering is not an option as the socket needs replacing. I repaired mine by soldering a short piece of insulated hookup wire from the pin to the socket and I will never have that problem again.
[Modified by jfb, 8:10 PM 1/19/2004]
[Modified by jfb, 8:10 PM 1/19/2004]
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (jfb)
Thanks for all the replies. My lamps are good. All four of them come on and off at the same time. Yesterday they came back for a while! Anyway, I noticed that the guy that repaired it for me had soldered two wires from one board to the other. He "jumpered" both of the end terminals. One appears to be a ground. I imagine that the other is the terminal that you jumpered. I'm hoping that he did a poor solder job. I'll try re-soldering it this weekend. :smash: It's such a hassle to go w/o the dash for the time it takes to have someone repair it that I'll pretty much try anything in order not to send it out again.
Thanks again!
Thanks again!
Pro
Joined: Sep 2003
Posts: 670
Likes: 1
From: charlotte nc
Re: '85 Instrument Cluster (Corvettaholic)
Corvetteholic, your problem is a simple? bulb replacement. There is a tech tip under tools for bulb replacement. You can access the bulbs after removing the outside plastic bezel without removing the dash cluster. They are under the shiny caps and you can simply pull them out. You should have no problem replacing the burnt out bulb yourself except for locating a suitable replacement. They're not easy to find and expensive when you do.
Jim's problem is a bit more complicated. It is likely due to a corroded ground pin connection between the two curcuit boards inside the dash module. There is a tech tip on this as well under tools. Following that tip, it is not difficult to take the dash out and clean the pins/contacts. These problems are usually due to bad grounds. I wasn't so lucky. I had a bad power supply which is best left to a pro. :cheers:
Jim's problem is a bit more complicated. It is likely due to a corroded ground pin connection between the two curcuit boards inside the dash module. There is a tech tip on this as well under tools. Following that tip, it is not difficult to take the dash out and clean the pins/contacts. These problems are usually due to bad grounds. I wasn't so lucky. I had a bad power supply which is best left to a pro. :cheers:
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
Re: '85 Instrument Cluster (Corvettaholic)
I ordered several from this business and the price was reasonable even with shipping. The reason it is less expensive is that you are buying the bulb and not the bulb and socket like GM sells replacements. Look up at Lamp Technology,INC. #882 by General Electrc. At your friendly GM dealer the bulb and socket is part #11508221.
Check it out at http://www.lamptech.com for the #882's.
Check it out at http://www.lamptech.com for the #882's.
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (jfb)
Well, I'm not having much luck. I finally got the cluster out today and tried to get power to the lights. If I use a battery and connect power to the circuit board where the lights connect I can get the lights lit. (I removed one bulb and connected a battery to where that bulb would connect...) But if I try to apply the power at that terminal, the one closest to the center of the board, I get nothing.
I have connected the board to the plug in the car and do not get 12 volts at any of those pins. At first I thought it was because when you first turn on the ignition, the lights are bright and then they dim. So, I probed each pin as I turned ont he ignition. I do have 7 volts at the fourth pin in from the center, but all the rest are low or no voltage.
I'm prepared to solder a wire from anywhere that I can get 12 volts to the positive side of the light circuit. I just need to know where to get that 12 volts from. Any ideas?
TIA
:banghead: :banghead: :nonod: :cry
[Modified by Jim Strathearn, 12:49 PM 1/30/2004]
I have connected the board to the plug in the car and do not get 12 volts at any of those pins. At first I thought it was because when you first turn on the ignition, the lights are bright and then they dim. So, I probed each pin as I turned ont he ignition. I do have 7 volts at the fourth pin in from the center, but all the rest are low or no voltage.
I'm prepared to solder a wire from anywhere that I can get 12 volts to the positive side of the light circuit. I just need to know where to get that 12 volts from. Any ideas?
TIA
:banghead: :banghead: :nonod: :cry
[Modified by Jim Strathearn, 12:49 PM 1/30/2004]
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: '85 Instrument Cluster (Jim Strathearn)
If you have the cluster out, then look at the rear circuit board (as the driver would see them) and look at the single row of pins that plug into the front board. If the socket is bad, then you will see discoloration of the circuit board around the pin closest to the center of the circuit board and you will see its solder has been melted. Solder a short piece of insulated hookup wire from the rear of the board on this pin and then solder the other end of the wire to the socket on the front of the front circuit board, same pin.
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (jfb)
Solder a short piece of insulated hookup wire from the rear of the board on this pin and then solder the other end of the wire to the socket on the front of the front circuit board, same pin.
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (Jim Strathearn)
OK - here's where I'm at now:
It appears that there may be a burned out resister in line with the circuit that provides voltage to the lamps. I tried to jumper it to see if I could light the lamps and drew sparks... :banghead: Anyway, I'm going to see if I can remove the resistor and get a replacement. It's pretty discolored and I';m not sure that the value will be able to be read by using the color coded stripes, most of which appear to be gone...
BTW, no, I'm not having fun yet... :nopity
It appears that there may be a burned out resister in line with the circuit that provides voltage to the lamps. I tried to jumper it to see if I could light the lamps and drew sparks... :banghead: Anyway, I'm going to see if I can remove the resistor and get a replacement. It's pretty discolored and I';m not sure that the value will be able to be read by using the color coded stripes, most of which appear to be gone...
BTW, no, I'm not having fun yet... :nopity
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: '85 Instrument Cluster (Jim Strathearn)
Maybe I'm confused, but the if you're working from the pins at the connector, then the middle ones - pin C5 - is the lights on input - C9 is the dimmer switch and D5 is memory. Power is at the top - C16 and D16 - from the Cluster Fuse (that isn't blown is it?).
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (SunCr)
Fuse is good. I'm getting voltage to that funny colored resister. But there is no voltage on the other side of the resister that goes to the light circuit. :smash: :banghead:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: '85 Instrument Cluster (Jim Strathearn)
The lamps are driven by a pulse width modulator which varies the brightness of the lamps through the dimmer control and the photocell. Batee has a circuit diagram for an 89 dash and I cannot find that circuit on his schematic. Probably your problems are in that circuit.
Thread Starter
Drifting
Joined: Feb 1999
Posts: 1,827
Likes: 0
From: Perpetually Lost PA
PA Events Coordinator
Cruise-In II Veteran
Re: '85 Instrument Cluster (jfb)
Thanks for all the help. I'm going to re-solder that resister in place and then reinstall the dash to see if I fubar'ed it. If it still doesn't light, I think I'll either try to purchase a couple of boards or bite the bullet and send it out for repair again. :smash: :banghead:
