Just finished a SS dash conversion on my 70 Chevelle this weekend. Everything went great and looks great with one exception. I have short and am blowing the Instrument Lamp fuse. Everything else functions normally including the exterior lighting, exterior signal, etc. I have no dash lights or internal turn signals. The clock is working but that takes power from a seperate lead.

During the conversion, I installed a new forward lamp harness, a reconditioned dash harness and assembled a cluster using repop parts. I suspect that the issue is related to the printed circuit and/or my assembly of the gauge cluster and its connections. They had epoxy glass insulators and I made assumptions when I put it all together.

Any suggestions that would help me to diagnose this problem? It would be appreciated.

I would start by removing the connector to the gauge cluster.
With your ohm meter check the load side of the inst light fuse to ground for a short.
No short - there is a problem with one of the gauge cluster light sockets or circuit board.
short - check the heater panel light, glove box light, console lights, headlamp switch, etc.

Went thru and did the tests Steve gave me and didnt find a short. Since I had pulled the dash earlier and checked grounds I thought I would give it another try. Put in a fuse and still no dash lights. Pulled the fuse again and found that it had not blown so I checked the load side of the Instrument Light fuse to check for voltage and their isnt any??? Does this mean I have a bad dash harness? Its a brand new Forward lamp harness. Does one particular pin in the forward lamp harness feed this circuit?

After reading a few posts, I will also add that I do have tail lights.

The PCB is different between gauge and non-gauge - did you update that?

The pinouts on the cluster plug are different between them also, but you should have that worked out if you replaced your dash harness with the correct unit. Did you also replace the engine wiring harness? I think there may be (not sure) some differences there also to accommodate the gauges.

Correct pinout on the cluster plug for gauges:
1-left turn signal
2-dash lights
3-ammeter-horn relay
4-ammeter-battery junction
5-high beam
6-oil pressure
7-power
8-brake light
9-tach
10-temp
11-fuel
12-right turn signal

Might want to check and make sure the plug pinouts are what you think they are.

Good luck!

Yes the PCB that I purchased was supposed to be correct for the cluster with guages. I checked voltage at the cluster plug. The only two places I have voltage are pins 3 and 4.
The problem lies down at the fuse box. No voltage to the Inst Fuse but I have taillights. Where does this fuse take its voltage from? Could I have a bad guage harness? It is the only component in the setup that was used.

Did you check at fuse itself?
Many times the fuse doesn't make good contact with its holder clips.

Yes. Checked both clips with and without the fuse and niether were hot.

Not at the clips, at the fuse end itself.
If the fuse doesn't make good contact to its holder clip, there will be nothing AT the clip.

Dean,

I will check it when I get home but if the clip itself isnt hot not sure how it would get to the fuse. Thanks for the help.

If the tail lights are working, the problem is likely with the head light switch (hdsw). As I'm sure you know the brightness of the dash lights is controlled by the dhsw knob. as you rotate the knob CCW the lights get brighter. Full CCW bypasses the resistor also turns on the courtesy lights. Rotate CCW but slightly before turning on the courtesy lights also bypasses the resistor. Try the bypass position.

I did that last night. There are no lights even at bypass but the dome light does come on at full CCW. For it to be the switch, it would have had to of failed during the swap as it was working when I pulled it. Which leads at the headlight connector should be hot? Maybe I could check there for voltage.

See the pic below. The orange wire is power in from the tail light fuse. The brown wire is out to the tail alights. Notice that there is a jumper that connects the tail light out, terminal 4, to the dash light rheostat in, terminal 3. The green wire is the rheostat out to the right hand side of the dash light fuse.

You can check for voltage on terminal 3. There is no wire in that location but you can still probe that slot with a volt meter.

http://www.chevelles.com/showroom/data/500/hl3.JPG

Elree,

Here is what I have...

Red - Constant Hot
White - Constant Hot
Orange - Constant Hot
Brown - Hot with Lights On
Lt Blue - Hot with Lights On
Green - Cold

So... No power at Green Wire = No power to Dash Light Fuse = Bad Light Switch???

Don't know why it wouldn't be, is the metal jumper in place? It connects the brown wire terminal to the rheostat in. The switch is working because you have power to the tail light output. That output is jumpered to the rheostat, with the switch CCW the rheostat is bypassed. If you have a short piece of wire jumper between the red and green. The dash lights should light. If not the switch is not the only problem.

Jumped the red and the green and got a light at the heater controls but nothing at the gauge cluster.

Just picked up a headlight switch and installed it. No difference. Still no dash lights even at the heater as I saw when I jumped the red and the green.

Sorry. I have all the dash lights when I jump the green and the red. Realized I forgot to reconnect the cluster connecter.

So... I have all my dash lights when I jump the red and the green but green isn't hot using two seperate headlight switches.

The original switch was working when I installed it and guess that there is a chance that the second is bad as well but I'm thinking there must be another cause that I am missing.

With the lights on verify voltage on the brown wire. Check for voltage at the rheostat in, use a short piece of wire or small screwdriver, if the volt meter lead end will not reach down into the unused connector opening. See revised pic.

IF there is voltage on the rheostat in and not on the green wire, remove the green wire from the connector for inspection. Make sure it makes a tight connection with the rheostat out terminal. If you are not familiar with the catch on the wire terminals see the second pic below.

http://www.chevelles.com/showroom/data/500/hl3.JPG

http://www.chevelles.com/showroom/data/500/70connects.jpg

Elree,

I dont have voltage on the brown or the rheostat in. Before I changed the switch I had voltage on the brown with the lights on.

I really appreciate your help with this!

Do you have voltage on the orange wire? If not check the tail light fuse.

Yes the orange wire is hot.

Here is what I have right now...

Red - Constant Hot
White - Constant Hot
Orange - Constant Hot
Brown - Cold (This is different since the switch replacement)
Lt Blue - Hot with Lights On
Green - Cold

Are the terminals in the switch connector clean? Are they making good tight connection to the switch connection blades?

Elree you are the man! Problem solved. Spade 5 on the switch was bent down and slipped outside the connector. Straightened it, plugged it up and its working.

Thanks for all the help. I never would have suspected the headlight switch.

Can someone mark this one "SOLVED"