New gauges dont work

So I ordered a brand new fuel, temp, oil pressure and amp gauge for my 68 charger from Classic Industries last year along with one of the solid state voltage limiters because it said one was required in their catalog for them to operate properly. I did omit the small capacitor when everything was installed as per the instructions that came with the new limiter. Anyways, fast forward to this past weekend, I start my car and the fuel, temp and oil pressure gauges don't work. The circuit board was in good shape with no loose pins, and I have tried grounding the sending unit wires to see if the gauges move to full and nothing happens. So my question is, if the new gauges are made to exact original specifications, why is the solid state limiter required? I have the old original limiter and capacitor that I could install to see if the gauges work, but don't want to burn them up. Is there a way to test a voltage limiter with a multimeter to determine if it is good?
Thanks for any help.

you need to make sure you are getting 12v to the circuit board.
if you can pull the cluster out and still have it plugged in, then use a multimeter, you should have 12v to the limiter and 5v going from the limiter through the circuit board to your gauges.

if you can't test it in the car, then just test for 12v with the key on at the correct location on the plug that feeds yr cluster.

use a 12v battery and alligator clips with the cluster out of the car to test for voltage from the limiter. if you really want to get fancy, use resistors inline with a ground wire and see if your gauges work.

Thanks for the reply. I will check for the 12v supply, It is a brand new dash harness so I hope there are no issues with it. If there are 12 volts going in and nothing coming out, I guess that narrows down my problem

Check your ground too.

If the car starts, then U at least have 12V coming through ignition switch. Next U need to check the connector from the ignition switch to the dash panel for 12V while being sure U have a good ground to the dash panel structure.... Often a pin or connector can have a bad connection be it oxidized or burnt or loose.

Regarding the voltage limiter, this is required as it drops 12V to 5V. The solid state limiter will work with new repro guages but not with the original OE guages as they will read low. It has to do with the basic guage meter movement, the original OE guages has a built-in thermal shunt system as to minmize needle movement with a voltage variation. Some people have argued with me about this but we have worked on multiple Mopar cars and actually have tried (2) different solid state voltage limiters with the OE original guages both read low. Plugged in an OE standard voltage limiter and all is well...

Just my $0.02...

Thanks for the replies, the car does start and run, dash lights all work and the tach works so I think the grounds are good. I will add another wire directly from the cluster housing to ground just to be sure, check for my 12v supply and 5v out. Just wondering if I got a crap regulator?

Bet the gauges are China made.

If the fuel gauge didn't read when you grounded the end at the tank you need to try grounding the input side of that gauge on the cluster to see if the wiring is the problem
I'm not sure on what the stock Mopar oil pressure gauge reads, ohms or mini volts

Cab..
Oil pressure, water temp and fuel gauges are all 5V DC movements...
As the gauge itself can be tested with a couple of D cells in series..
Each respective sending sensor is simply a variable resistor. Though some early 70s' A bodies have the voltage limiter built into the fuel gauge.

Just my $0.02...

U can easily check the voltage limiter...
Look closely @ the terminals, 12V+, ground and 5V, connect up 12V+ & 12V- check to see if it has 5V output...

Just my $0.02...

So, update on this. I went out last night and was able to reach up under the dash, pulled the current regulator out and hooked it up to the battery, had a steady 5v output. Went back under the dash with the Fluke and measured for my 12v supply, that was good. It does feel like the regulator plugs in rather easily, so it must have not had good contact before, think I will pull it back out and put a slight twist in the prongs or something to help it "stick" better. Now the fuel, temp and oil pressure gauge work
Again, thank you all for your input.

Great..
Happy to help..
Many of the local SoCal Mopar guys contact me about their electrical issues. Actually troubleshooting the old Mopars electrical systems is straight forward compared to the newer computer based cars. The majority of issues are switches, bad grounds, loose connectors, bulkhead terminals. But major challenges are when an inexperienced person messes with things, then things can get difficult.
Take care.

Just my $0.02...