Topic: Gauge lights
in Forum: C3 Electrical
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It has been talked about a few times, but I didn't find the answer I was looking for through the forums.
Problem : lights out on all lights behing the gauges (only the single gray wires; not the "head light" and "the_other_one_next_to_it"; which are dbl wires).
Background info : I replaced the original radio with a Corvette Kenwood unit (which works fine). I used the original radio wires (black and yellow) as well as the lighter for the secondary power (orange) required by newer radios. The gray wire that used to be connected to the old radio is exposed (not connected to anything), but "protected" with a piece of electric tape.
The gauge lights won't come up anymore. Everything else works. These gauge lights (as far as I know) goes to a 5a fuse (that I replaced with a new one) and from there, goes to the light switch.
The current reading at the gray wires (when I remove the bulb) is 0 volts. I did not take a reading at the fuse. (not exactly sure how; where do you connect the ground of the reader and where do you test the fuse itself vs the fuse box??).
I replaced the headlight switch with the same results. All other switch function works well; dim lights, headlights and dash light indicating "head lights" in the cluster. Everything BUT all the single gray wires (I think it's 6 of them, including the one within the transmission console and the one for the old radio.
Any clue ?
I know I have to take a reading at the fuse, fuse box and the switch; just not sure exactly how and what to expect.
I "might" have pinched a wire trying to put the new radio in (You have no idea how much swearing was involved in this one...). By feeling them it all looks okay, but I know it wouldn't take a big cut to create problems. Is there a way to verify this other than "feeling it"?
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The gauge lights or insturment panel lights, are fed from the parking light circuit. Be sure the park lights are on first. They have a seperate fuse.
Lifetime MemberFrederick, MD - USA
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Ken....
I really do not understand whay you mean make sure the parking lights are on also...
I lost the dash lights on my 72 in April or May...and added it to the list
of things to "fix" this winter... All I have done this summer is to check the fuses...parking lights, Headights,directionals etc work fine as do the other interior lights... Purchased a laminated wiring diagram at Carlisle
and a dash switch under the asumption that was my problem..
Bob G.
Bob
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Stephane, to check the voltage at the fuse, the park lights must be on(as Ken says), then ground your test light/volt meter to a known good ground. Any metal panel under the dash should work for this. Then test both ends of the fuses. It should light up on both ends. If it lights on one end, but not the other, the fuse is bad.
Are the lights for the speedo/tach still working?
Just looking at a fuse doesn't always give a good indication of its integrity. Use an ohm-meter to check fuses, with the fuse out of the car.
If the fuse is good on both ends, and you have no panel lights, check to make sure they're all plugged in really well, and the panel has a good ground, still.
I'm going to check some stuff on the wiring diag., and I'll get back with some other info. 'Till then, use a flashlight!
I'm Baaaaaack!
Here's what the wiring diag. shows, as far as instrument panel lighting.
All of the panel lights are powered on the grey wires. The grey wires come from the fuse box, off of a 4amp fuse labled "Inst. Lmps". That fuse is fed from the headlight switch on a dark green wire from the switch, to the "Inst. Lmps" fuse, and then on to the lamps themselves. This is why the lights(parking lamps) need to be on for the inst. lamps to work. The fuse will not be "hot" if the parking lights are not on.
The grey wire you left off of the old radio is the radio light wire. It should not be a problem to leave it disconnected, as long as it is insulated.
It appears that there are two "splices" for all of the inst. lmps. One of them feeds the gauge panel, and the other goes to the speedo/tach panel. If it was a fuse/switch related problem, NONE of the lamps would work. If the speedo/tach lights work, then you have a loose connection at the gauge panel, somewhere.
I hope this helps narrow down the search!
Adams' Apple 38619.7962268519
Are the lights for the speedo/tach still working?
Just looking at a fuse doesn't always give a good indication of its integrity. Use an ohm-meter to check fuses, with the fuse out of the car.
If the fuse is good on both ends, and you have no panel lights, check to make sure they're all plugged in really well, and the panel has a good ground, still.
I'm going to check some stuff on the wiring diag., and I'll get back with some other info. 'Till then, use a flashlight!
I'm Baaaaaack!
Here's what the wiring diag. shows, as far as instrument panel lighting.
All of the panel lights are powered on the grey wires. The grey wires come from the fuse box, off of a 4amp fuse labled "Inst. Lmps". That fuse is fed from the headlight switch on a dark green wire from the switch, to the "Inst. Lmps" fuse, and then on to the lamps themselves. This is why the lights(parking lamps) need to be on for the inst. lamps to work. The fuse will not be "hot" if the parking lights are not on.
The grey wire you left off of the old radio is the radio light wire. It should not be a problem to leave it disconnected, as long as it is insulated.
It appears that there are two "splices" for all of the inst. lmps. One of them feeds the gauge panel, and the other goes to the speedo/tach panel. If it was a fuse/switch related problem, NONE of the lamps would work. If the speedo/tach lights work, then you have a loose connection at the gauge panel, somewhere.
I hope this helps narrow down the search!
Joel Adams
C3VR Lifetime Member #56 
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Wow, I need to get myself this wiring diagram. I have seen it on websites here and there, but now... I'm getting one!
It's starting to make sense now.
I didn't think it was usefull info, but to be able to pull the cluster out, I had to move the whole middle too, which required me to put the transmission out of park (with the emergency brake on of course).
Not sure about the speedo/tach, but I think they were off as well. Which means it could be another fuse.
About the headlight switch, the prongs are numbered, but I couldn't find any description of what they mean. I think there was about 7 or 8 of them. (And btw, when buying a replacement headlight switch at a local car parts, make sure there's the vacuum plugs on them, mine didn't; have to return it now...)
Allright, I have more than enough to play with tomorrow. I'll let you know what I find out. Thanks for all the info and research time, I really appreciate.
Update (didn't mention before):
My fuse box says 5a, but the book says 4a. I tried a 4, a 5 and 7.5; same result.
I'll rather stick with 5 because the box says so, but it's confusing. (Don't worry, the 7.5 is out; it was just a test
)
I'll rather stick with 5 because the box says so, but it's confusing. (Don't worry, the 7.5 is out; it was just a test)No one has mentioned, or maybe I missed it, checking to make sure the
cluster is grounded. It has to have a ground to get the lights to work.
Check to make sure the ground wire is connected good.
Still confused....
Tonight, I checked the fuse (with an ohm meter)... and ... good fuse! (is there really a difference between AGA and AGC ???).
The speedo/tack have light, but still not at the cluster.
Without the fuse in the box (5 amps in my case for a 74 instead of 4 amps), there was no current at all (with the key and light switch on).
Is the 74 supposed to have a circuit breaker (like the Chilton & Haynes books says, cause I could not locate it) ?
I tried to pull the fuse box out, (two screws), but could not pull it out enough, something behind the firewall (in a box) is holding it ... I think).
2 questions :
- Is the console ground we are talking about under the transmission console ?
- what do you guys mean by "park lights" ?
Thanks!
The original radio black wire was also the wire that grounded the gage cluster. Once you took the radio out you will need to run a ground the the cluster and connect it to a good ground. I had the same issue when the Po replaced the radio and didn't ground the cluster. I attached a ground wire to the back of the cluster and attached to the metal peice under the instrument panel. Also me gages did not work right because until I did that. The temp gage would change everytuime I turned on the lights because it was back feeding through the lights.
Brian - NCM Lifetime Member
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Member: NCRS, NCRS Texas, Corvette Legends of Texas
[QUOTE=74-454] ..........
.......
The "circuit breaker" is actually part of the headlight switch. This is not going to be your problem, tho.
The fuse box is held in by a bolt thru it from the engine side of the firewall. Also not going to be your problem
"Park lights" is what some people call 'running lights'. If you pull the headlight switch out to the first position, you have only the "park/running" lights on. The second position(all the way out) turns on the headlights, also.
You have a ground problem with your center gauge cluster, and that is why the lights for the gauges are not working, but the tach/speedo lights are. With the tach/speedo lights working, it means the light switch is good, as well as the fuse(s) for the inst. lights.
If you have the wiring diagram for your car, you should be able to find where the ground is for the cluster, and trace it from there. I'll look at my diagrams and see if I can give any more help with that. ("I'll be bach!" )
Brian(redwingvette) is correct!! The ground for the cluster IS the same as the one for the radio. If you still have the connector for the orig. radio, it will have 3 wires. Grey, black, and yellow. The grey wire is for the light in the radio: the yellow is for power: the black is ground. It goes to a "console ground". You should have a connector on the back of the cluster with two black wires comming from it. These wires splice into the black wire from the radio, and then it goes to ground. I think you can just do what Brain said, and run a separate wire from a good grounded spot to the black wires, and be in business, if you can't locate the original ground spot. It will be under the center console, and the diagram shows two black wires connected at that spot. It is this terminal that is causing you to be "in the dark"!
Hope this makes some kind of sense!
btw....this same ground is used for the cluster ground, which explains why Brian's gauges didn't work correctly until he grounded the cluster. Adams' Apple 38625.8063194444
Is the 74 supposed to have a circuit breaker (like the Chilton & Haynes books says, cause I could not locate it) ?
I tried to pull the fuse box out, (two screws), but could not pull it out enough, something behind the firewall (in a box) is holding it ... I think).
.......
- what do you guys mean by "park lights" ?
Thanks!
[/QUOTE]
The "circuit breaker" is actually part of the headlight switch. This is not going to be your problem, tho.
The fuse box is held in by a bolt thru it from the engine side of the firewall. Also not going to be your problem
"Park lights" is what some people call 'running lights'. If you pull the headlight switch out to the first position, you have only the "park/running" lights on. The second position(all the way out) turns on the headlights, also.
You have a ground problem with your center gauge cluster, and that is why the lights for the gauges are not working, but the tach/speedo lights are. With the tach/speedo lights working, it means the light switch is good, as well as the fuse(s) for the inst. lights.
If you have the wiring diagram for your car, you should be able to find where the ground is for the cluster, and trace it from there. I'll look at my diagrams and see if I can give any more help with that. ("I'll be bach!"
)
Brian(redwingvette) is correct!! The ground for the cluster IS the same as the one for the radio. If you still have the connector for the orig. radio, it will have 3 wires. Grey, black, and yellow. The grey wire is for the light in the radio: the yellow is for power: the black is ground. It goes to a "console ground". You should have a connector on the back of the cluster with two black wires comming from it. These wires splice into the black wire from the radio, and then it goes to ground. I think you can just do what Brain said, and run a separate wire from a good grounded spot to the black wires, and be in business, if you can't locate the original ground spot. It will be under the center console, and the diagram shows two black wires connected at that spot. It is this terminal that is causing you to be "in the dark"!
Hope this makes some kind of sense!
btw....this same ground is used for the cluster ground, which explains why Brian's gauges didn't work correctly until he grounded the cluster.
Joel Adams
C3VR Lifetime Member #56
My Link
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
WOW, thanks for this research. I have many wiring diagrams from books, but they always seems to "skip" the cluster and most of the grounds. 10 minutes ago, I ordered a full size (and color) wiring diagram from http://www.classiccarwiring.com/ (sorry for the free publicity).
About an hour ago, I tried what Brian suggested, but I didn't do it from the 2 black wires; I simply hooked one side (of a 14 gauge wire) under one of the console retaining screw down to a metal plate under transmission console. Now... obviously, it didn't work!
I didn't know about these 2 black wires. Will try tomorrow.
I didn't know about these 2 black wires. Will try tomorrow.Funny, I was re-reading the thread and realized that Eddie was right on the money in the first place, but I didn't understand "grounding the cluster"; I figured that if I didn't touch anything else but the radio, the cluster had nothing to do with it.
I call the "park lights" the "dim lights"; but what the heck do I know, english is not my mother tongue and car lingo is new as well. You guys should hear the words I make up sometimes trying to explain what I'm looking for. Kudo to all the local parts store clerks who have the patience to deal with me trying to decypher "that little round thing that makes 'click' when you push/twist on it..."
; but what the heck do I know, english is not my mother tongue and car lingo is new as well. You guys should hear the words I make up sometimes trying to explain what I'm looking for. Kudo to all the local parts store clerks who have the patience to deal with me trying to decypher "that little round thing that makes 'click' when you push/twist on it..." Thanks again for all the help.
in Forum: C3 Electrical
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