Bench testing a cluster

[jb73Mach]

Anyone have any advice or experience bench testing lighting in a cluster? It looks like I should be able to apply voltage to the proper + and - wires on the PC and then look at the results. Does anyone know the voltage and a good source to provide it?

After I fixed the odometer button, I decided to go with LEDs while everything was out.

 

[Don C]

You'll need 12 volts. Depending on the LEDs, they may be polarity sensitive. The fully charged car battery will work. Be careful, 12 volts will cook the gauges (they run off reduced voltage).

 

[midlife]

With bench testing lighting, pay special attention to the ground: those poor lil' electrons need some where to go home!

 

[jb73Mach]

You'll need 12 volts. Depending on the LEDs, they may be polarity sensitive. The fully charged car battery will work. Be careful, 12 volts will cook the gauges (they run off reduced voltage).

So the lighting doesn't run through the voltage limiter and uses a full 12 volts? The LEDs are polarity sensitive and I want to make sure I didn;t get anything backwards.

 

[Don C]

The dash lights just run through a rheostat on the headlight switch to control brightness, and on full bright are close to battery voltage.

 

[jb73Mach]

Don,

If I'm careful, do you think a batter charger at 2-4 amps would provide enough to bench test? I have a great diagram from HiPo parts that came with the LEDs that identifies all of the + and - lines for turn signals, brake and high beam lights as well as the general lighting.

 

[midlife]

Current is controlled entirely by the resistance of the circuit and not by the capacity of the voltage source. You can't push more current than what is needed through a device, but you can push more voltage through it. The battery charger is a voltage source that has a current limiter as an added feature...it is not a current source.

 

[Don C]

For LEDs a couple of amps should be enough. Some "smart" battery chargers won't produce voltage unless they are connected to a battery.

 

[jb73Mach]

Curses, foiled again. I bought replacement bulb sockets for a half dozen that were loose or had bad contacts. The new sockets looked right so I opened them and painted the positive side to make the process easier. The contacts seem to be off about 30 degrees. They line up nicely in between the copper contacts on the PC instead of actually contacting the copper strips. I guess I'll have to clean and adjust the old ones and hope for the best. Now the bench test is going to be even more important.

 

[Eags 73]

Curses, foiled again. I bought replacement bulb sockets for a half dozen that were loose or had bad contacts. The new sockets looked right so I opened them and painted the positive side to make the process easier. The contacts seem to be off about 30 degrees. They line up nicely in between the copper contacts on the PC instead of actually contacting the copper strips. I guess I'll have to clean and adjust the old ones and hope for the best. Now the bench test is going to be even more important.

I found that the led bulbs would not always make a good connection to the sockets and had to bend the little lead wires around a bit to make them work. I used a 12 volt start pack to bench test mine, I attached alligator clip jumper wires to the battery clamps being careful not to let them touch each other or ground out to the car frame. I carefully attached the other end of the clips to the pc. I will try to attach a picture of the pc I mapped out. Attach negative to "c" and positive to "dimmed lites".

 

[jb73Mach]

I only had one that needed to be torqued a bit to get good contact. The kit I bought had a great circuit map for the lighting and it only took a couple of minutes to mark the rest for testing. I ended up using a battery charger and leads. The kit had green LEDs for the turn signals, red for the brake and high beam indicators, and white for the rest. As long as the blue diffuser bulbs are still good, the color is factory correct on the gauges. I was fairly happy with the results. I have attached a picture of the entire PC map.

 

[73StangCoupe]

I only had one that needed to be torqued a bit to get good contact. The kit I bought had a great circuit map for the lighting and it only took a couple of minutes to mark the rest for testing. I ended up using a battery charger and leads. The kit had green LEDs for the turn signals, red for the brake and high beam indicators, and white for the rest. As long as the blue diffuser bulbs are still good, the color is factory correct on the gauges. I was fairly happy with the results. I have attached a picture of the entire PC map.

JB,

I bought and installed the same kit for my 73 Coupe from HiPo parts. I'm at the point where I'd like to bench test my new bulbs. Or would it be easier to just plug it back in to test all the lights at once?? I may not be understanding what you had to do, but it looks to me like you had to test each bulb individually. I'm not familiar with doing things like this. Please let me know what you think would be easier, thanks...

 

[jb73Mach]

All of the normal gauge lights are on one circuit so you would test 1 and 3 for gauge illumination. You would have to test each turn signal, oil light, etc separately. 3 is the common ground and each individual light is identified. I had a contact for the gas gauge that had separated from the PC backing and the foil alone was very fragile so I wanted to avoid too many in and outs. As it turned out, I had to take it in and out several times because I knocked bulbs out when installing the cluster. Since the LEDs are polarized, I couldn't see to make sure that I got them back in right without the cluster out.

Long and short, it might just be easier to test them by plugging the cluster back in at least if you install things like I did (badly!). I also had some trouble getting the speedometer cable to sit right. First drive, the needle bounced all over. I pulled the cluster out (again) and reseated the cable. That took care of the problem.

One other tip - just put one screw in by the turn signal indicators and one at the bottom when testing the bulbs and the speedo (much faster to get it back out if necessary.)

 

[73StangCoupe]

Thanks JB... I'm taking the day off tomorrow to work on the car. I'll try the bench test first. If that doesn't work out I'll hook the battery up and plug the cluster in to test the bulbs. I appreciate your help on this. I'll let you know how it works out. I still have bit of painting to do, the I can start putting this puzzle back together again.