Some quick points: - I've done my homework, I'm aware there are some threads on problems with gauges in the FAQs. I referenced this one heavily to get where I am: "Stock Cluster to a Rally Gauge Cluster". Read some of the other threads as well - My car has been converted from Idiot Lights to Rally gauges by a previous owner, confirmed using article above - All gauges worked previously to my most recent change, no guarantee on the readings but they worked, I am reasonably sure the Temp gauge was pretty close - I have changed nothing about the way the cluster is wired up (yet)
I'm posting here hoping someone or the group can help me step through a troubleshooting process logically. I'd like to learn some things and do this right. I took Basic Electronics during Tech School for the Air Force in the early 90s and passed the class with a 98%. Now I can barely use a multimeter <sigh>.
Problem occurred after I installed a new Dash Bezel (plastic one that surrounds the two pods). The one on the car looked bad and I bought a new one. All the gauges worked before I took them out. I took out the gauge cluster, remove the plastic bezel and also removed the clear plastic lens to clean them and polish them up. Reassembled everything with the new bezel and put it back in the dash. Nothing works. Not any of the gauges. Just the speedometer since that uses the mechanical cable.
Using the information I found here I pulled the gauge cluster back out. First I verified the wiring for the 12-pin connector. It fits the cluster fine but the wire colors are completely wrong. I'm thinking it might be from a '69 Firebird. Maybe someone can verify. I also noticed every wire from the connector was spliced into a wire from the harness. Pretty much verified someone changed the car from idiot lights to Rally gauges. Here's the wire map:
Pin 1: Tan Wire ---> Dark Blue Wire w/White Stripe (Oil Pressure Gauge) Pin 2: Grey Wire ---> Two Dark Green Wires (the one grey wire is spliced to two Dk Grn wires) (Water Temp Gauge) Pin 3: Black Wire ---> Tan Wire (Fuel Gauge) Pin 4: Light Green Wire ---> Grey Wire (Illumination) Pin 5: Two Dark Blue Wires w/ White Strip ---> Terminated and wrapped with tape, unused Pin 6: Two Light Blue Wires ---> Terminated and wrapped with tape, unused (Illumination)
Pin 7: Dark Blue Wire ---> Light Blue Wire (Left Turn Light) Pin 8: Orange Wire w/ Black Stripe ---> Tan Wire (Brake Light) Pin 9: Tan Wire ---> Medium Blue Wire (Right Turn Light) Pin 10: 2 Dark Green Wires (+12V DC) ---> First Dark Green Wire ---> Pink Wire from factory harness ---> Second Dark Green Wire ---> Light Blue Wire that goes to the firewall is spliced into a Black Wire w/ White Stripe that goes through the firewall into the engine compartment (I have not yet traced this wire) Pin 11: Brown Wire ---> Terminated and wrapped with tape, unused (Volt Gauge) Pin 12: Two Pink Wires ---> Brown Wire in the factory harness (Volt Gauge)
All the connections above (save for the Pin 10, 2nd green wire that runs to and through the firewall) are splices from the 12-pin connector directly to wires coming out of factory dash harness. If you reference the article above you'll see that the factory harness wires are spliced to the correct Pin in every case with the following exceptions:
- Pin 2 was connected to two green wires for idiot lights but only one for rally gauges. whoever did this conversion connected the Pin 2 wire to both green wires anyway - Pin 6 is normally connected to a 2nd gray wire for cluster illumination whereas here the wires from this pin were just terminated and not used - Pin 10 should only be a single Pink wire. Whoever did this conversion connected the two green wires coming out of this pin on this connector to the Pink wire and the Light Blue wire that runs through the firewall into the engine compartment - Pin 11 should be a White wire used for the Volt Gauge, whereas the brown wire coming from this pin is terminated and unused - Pin 12 should be a Black wire used for the Volt Gauge. The two Pink wires coming from this Pin are spliced into the Brown wire coming from the Factory Harness that was used for the Generator light in the Idiot light setup. According to the article this Brown wire runs to the Voltage Regulator so I suspect this is how they were getting the Volt Gauge to work.
I know this was not done in accordance with the article here BUT please remember all the gauges worked previously. Could it be done better? Yes. In the long term I will probably replace the engine side and dash harness both to make the car correct for a Rally Gauge car. Right now I'd just like to get the gauges working again. Whoever did this, did install sending units and made the necessary changes on the engine side to get the gauges to work as they worked before.
For a ground the same person (presumably) ran a black ground wire from the upper rightmost bolt that is used to hold the PCB in place on the cluster housing to a bare metal spot on the firewall. I figure most or at least some here in the forum will suspect a ground issue. I don't disagree but will need some help chasing that down. I don't fully understand yet how the 12V DC is used within the cluster and how to measure it as it works through the PCB for the cluster.
By the way, the PCB has two bad tracks that someone soldered (I have ordered a new one from AMES), however the tracks in question are for the left and right turn light or brake light. I traced them. Should not be a factor for the gauges, esp considering that, as I have mentioned, all the gauges worked before I pulled the cluster out.
So things I've done: - checked the fuse and it checked good, 0.00 resistance on the multimeter AND I replaced it anyway - verified exactly how the 12-pin connector is installed in the cluster. I didn't know this at first because when I removed the connector I couldn't see how it was oriented. Researching here I found Pin 1 must be in the upper left corner so that pins 1-6 are on top running left to right and pins 7-12 are on bottom running right to left. I was amazed at how many diagrams and other references I looked at that had the pinouts for the Rally gauges but did not say which way to install the connector. - changed the fuse, verified I had the 12-pin connector installed correctly, turned the key to accessory and also started the car, none of the gauges functioned - I removed the connector and put the key back to accessory and checked Pin 10 where the 12V DC is supposed to come in and got 12.74 on the multimeter
That's where I have stopped for now. The wires are long enough in the dash that I can connect it to the cluster without having to stick the cluster back in the dash so I am hoping this will help with troubleshooting. I'd like to get the gauges working again and then I'll see what I can do to clean up the wiring.
Well darn, I thought we had a bunch of guys on here good at troubleshooting gauges. My thought was to test each gauge, hoped to get some help with that too but really shouldn't be necessary since they all worked prior to the bezel install.
I have a 68 convertible with Ralley gauges and also have a two year electronic degree. I worked in San Antonio a few weeks ago for 8 day too:)
Anyway, I can't seem to find any of my wiring notes, but from memory none of the factory wiring diagrams available will show a rally gauge setup, however many of the colors will be the same.
My car did not come factory with rally gauges. I bought a set off ebay and bought all new wiring harness from M&H for my whole car and a new printed circuit board.. Even with new wires I had a bunch of issues with my gauges. Mostly because I painted the metal gauge pod and none of the grounds worked.
Since it sounds like you have power at the plug I would new focus on the gauges. What I did with mine was trace out the printed circuit on paper along with what gauge it went to. I also used a 9 volt batter, a 100 ohm pot and some alligator clips to test the gas, oil gauge and lights. DO NOT USE IT TO TEST THE AMP METER.
Tracing out the circuit on paper will make the issue clear of what might be going on.
If I remember correctly the 12V feed everything. The functions are based on grounding. So for example 12V goes out to the gas tank sending unit on the Tan wire through the 90 ohm wire resister and then grounded.
Sounds to me like you may have a damaged printed circuit board.
The question I would ask is why would you need to rewire if the gauges previously worked and you didn't change those connections? I think you are on the right track with the PCB or the ground as those are more likely to impact all the gauges.
1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)
Did you ever get your Amnmeter gage to work connecting to the green volt reg. wire instead the battery junction block as described in the conversion write up?
I have a 68 convertible with Ralley gauges and also have a two year electronic degree. I worked in San Antonio a few weeks ago for 8 day too:)
Anyway, I can't seem to find any of my wiring notes, but from memory none of the factory wiring diagrams available will show a rally gauge setup, however many of the colors will be the same.
My car did not come factory with rally gauges. I bought a set off ebay and bought all new wiring harness from M&H for my whole car and a new printed circuit board.. Even with new wires I had a bunch of issues with my gauges. Mostly because I painted the metal gauge pod and none of the grounds worked.
Since it sounds like you have power at the plug I would new focus on the gauges. What I did with mine was trace out the printed circuit on paper along with what gauge it went to. I also used a 9 volt batter, a 100 ohm pot and some alligator clips to test the gas, oil gauge and lights. DO NOT USE IT TO TEST THE AMP METER.
Tracing out the circuit on paper will make the issue clear of what might be going on.
If I remember correctly the 12V feed everything. The functions are based on grounding. So for example 12V goes out to the gas tank sending unit on the Tan wire through the 90 ohm wire resister and then grounded.
Sounds to me like you may have a damaged printed circuit board.
Rorht, your right. I have a 68 Service Manual and one of those tri-fold wiring diagrams. Both are for the wiring for the idiot light setup. I have not see a wiring diagram that includes the wiring breakout and colors for Rally gauges. Oversight by GM?
I bought an engine wiring harness for my 73 Trans Am from M&H. They do really good work. I'm having some issues with Ames, so even though I ordered a new PCB last Thursday I still don't have a new one. Trying to get that worked out.
I'll take your advice on tracing the gauges. I went to radio shack to get a battery and potentiometer. When I read 9V battery here I was thinking of those small squareish batteries you could buy in the past that were about the size of a coffee can? When I got there I asked about 9V batteries and he brought me the little square 9V batteries you put in a smoke alarm for the house. I felt pretty dumb. Is that what you used? I'm going to try that first. Radio Shack did have a very small square lead acid 12V battery for $22. I may go get one of those. Would be perfect for testing these kinds of things albeit a little heavy.
I couldn't remember what you got for a Pot so I got one of the smallest ones they had, that had a post you could roll with your fingers. Its 5k Ohm, 500VDC and .5W. I'm guessing its just overkill for this application but should still work. If you got a 100ohm Pot for a reason, please let me know. I also picked up some alligator clips.
I had some questions on how you did this testing. I am assuming here the Pot is to vary the amount of voltage fed to the gauge. So completely counter-clockwise the Pot is sending 0V and completely clockwise it is sending the full 12V.
If that's correct, I should be good to test but I am curious what varies the voltage for each gauge. Say the gas gauge. If there is 12V coming in on Pin 10, what is controlling the variation of voltage fed to the gauge? The other wire coming from the Sending Unit? So for the gas gauge you have 12V coming in on Pin 10 and then what the "Control Signal" from the gas tank sending unit on Pin 3?
I'd like to better understand how the 12V and the sending unit interact to put the needle where it is supposed to be on the gauge. You also mentioned a 90 ohm wire resistor. Where is that located? In the gauge? Sending unit? I know the purpose of a resistor is to introduce a certain amount of resistance into the circuit. Is this the control signal? Resistors are usually a static value that does not change so I am not sure how that would be used to vary the voltage.
The question I would ask is why would you need to rewire if the gauges previously worked and you didn't change those connections? I think you are on the right track with the PCB or the ground as those are more likely to impact all the gauges.
Well the short answer is I don't. I just hate the fact that someone didn't take the time to find a 12-pin connector that was correct for this application. So the wires you see coming out of are completely the wrong color. Thankfully I could see the wires coming out of the factory harness so I was able to make sense of it all. I'm also a little OCD with these kinds of things. So after I get it fixed I may change out the wires for the correct colors but since that would be a PITA, I'll prob wait till I can get the correct harnesses.
I figured it out tonight. I used my multimeter and did a continuity check of every track on the PCB starting with the two that had been soldered. I found that the track from Pin 10 that supplies 12V to everything was completely broken where the track gets very close to the edge of the PCB at the bottom. SInce everything worked before I can only assume that this is self inflicted. I must have hung it up on something re-installing and cause the track to separate. I'm going to solder a piece of wire on it and order a new PCB. That should take care of it.
Hmmm, must have bumped it while, pulling it out or putting it back in. Does it make sense to redo the dash harness at the same time? Ouch, they ain't cheap.
Last edited by wovenweb; 06/05/1508:06 AM.
1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)