Instrument cluster bench test

[DSwan]

I'm converting my old burned out dash lights to LED lights and was wondering if there's an easy way to test the cluster before installing it to make sure the light bulbs are working okay. I've already installed it once and found some weren't working, and it's a PITA to go back and forth with it. It would be much easier to do if I could hook up a battery and check it first. I tried the link someone posted some time ago and it doesn't pull the video up anymore.

Thanks

 

[midlife]

There is a way, but you're likely to cause more damage to the circuit card than it is worth the check for lights.  Use alligator clips for the blue/red wire lead and the ground lead.  The pins vary from standard dash cluster to tach dash cluster.

 

[DSwan]

I don't see any wires on the cluster once it's removed. It didn't have the tach originally. I thought maybe a person could use a battery to check by touching off on the copper runs in the circuit board?

 

[1sostatic]

One tiny  job in my life is designing test equipment - surely a jig  can be made that delivers the electrical values and simulated signals that the dash cluster requires.? 

 

[tony-muscle]

Last week I received an email for this gadget to test gauges. 

https://secure.cougarpartscatalog.com/17702/31802/gauge-tester-repro-1967-1968-1969-1970-1971-1972-1973-mercury-cougar-ford-mustang.html

 

[Don C]

It wouldn't take much to build one. The easiest would be to have the connectors, otherwise you would need to build a spring loaded plug that makes contact with the ribbons, or use alligator clips to connect to each gauge, you would need a 5 volt power source and 10, 40, and 70 ohm resistors. By starting the test at the connectors you would also be testing the circuit board at the same time.

Edit, or buy the tester that Tony linked.

 

[midlife]

That tester is great, but is useful only for the oil, water and fuel gauges.  The OP asked about testing his new LED lamps.  I thought about it some more, and there is a way: Find the bulb (1895) that comes from a red molded 2 pin connector.  I believe this is for the heater switch light.  Disconnect the connector and feed +12V to the blue/red wire (female side) and ground to the black pin (male bullet) or to the chassis.  That should energize all of the dash lamps on the circuit.  Probably best to disconnect the headlight switch connector, as I don't know if there would be any feedback issues there. 

 

[nursieee]

I burned one circuit one the p.c when trying that so be careful.

 

[7173Vert]

Just going through a bit of this now. Changed out my gauge cluster to the Hi-Po LED’s, worked great. Then changed out the original AM radio to an AM Cassette I had. Now the 4amp gauge cluster and other lights fuse keeps blowing... I’m wondering if how I hooked up the AM Cassette to the original AM power supply lead is causing the problem? I hooked the main power and the unit ground wire to the plug... When I check with a test light, I don’t seem to have any power at the 4 amp fuse circuit at all now, no matter where the key is turned too.  I haven’t looked at the electrical diagram yet, but, it is something to do with the radio install as that 4 amp light circuit was working fine before I thought I was an electrician... 

 

[midlife]

If you believe the ground line is one of the two leads going to the AM cassette, you're wrong.  The two leads are fused power and fused lamps.  Ground is via the chassis.

 

[7173Vert]

If you believe the ground line is one of the two leads going to the AM cassette, you're wrong.  The two leads are fused power and fused lamps.  Ground is via the chassis.

Yes. Figured that out this morning.... When in a rush, take a step back and think. All good now. Thanks.

 

[midlife]

Must not have had your Tim Horton's coffee, eh?

 

[7173Vert]

Must not have had your Tim Horton's coffee, eh?

I think I had two by that time... The car has been on the scissor lift for three months now. Just these little jobs left of hooking up some interior pieces to get the car completed and back riding on its own rubber. Just a dumb mistake. The hardest part was finding new 4 amp glass fuses. I had to go to my local store and order one pack of five... Another 24 hr wait for these to come in. Like your sense of humour in any event...

 

[nailpounder]

use a new 9 volt battery with wires taped to the terminals     then touch the wires to the  plug aria of the circuit board    you can see the path of the  circuit for the lights  the leds are polar sensitive  the ground runs along the out side of the circuit board  if i remember right 

 

[DSwan]

Thank you. I did that and it showed me the way. I found the ground terminal first, then the branch running to the lights. Easy to change the polarity of the ones not lit, and I even was able to get the brights indicator and turn signals working while still on the bench. I now have to track and find why I'm not getting power to the positive for the instrument lights at the plug and why my gas gauge isn't working anymore. I thought I may have shorted out the constant voltage regulator so I replaced that again, but still not working. I'm going to check the light switch, but I don't think that would have anything to do with the gas gauge. Always something.

Thanks again everyone. I certainly appreciate the help.

 

[SteveO_71]

This diagram may help even though it has the tach:

 

[DSwan]

Thank you. Ordered new light switch because all of a sudden the dome light isn't getting voltage.

 

[DSwan]

Update to everyone who helped me on these pesky issues: After finding the way to test all of the instrument cluster lights, I was able to get all of the lights working - even the turn signals and bright lights indicator. The problem with them not working when I re-installed the cluster into the dash turned out to be the headlight switch. The gas gauge was another issue. I tried to find a remanufactured gauge, to no avail, so I ended up taking mine apart. I found that there's a very fine wire inside connecting the two terminal posts, and one of them was disconnected, probably when I was removing the nut/washers to replace the circuit board and CVR. I found a window defroster wire repair kit at my local auto parts store and it worked to re-attach the wire, then I added a drop of liquid electrical tape to make sure it didn't come loose again. The dash is back to functional again!

Thanks again to everyone.