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No dash lights

 
chevelleman63 chevelleman63
New User | Posts: 21 | Joined: 11/11
Posted: 12/14/12
05:41 PM

Have 72 chevelle ss,can't seem to get dash lights to work.I have put in a new printed circuit ,made sure all bulbs were good,installed new headlight switch and have two ground wires @brake assy.I have all other lights working including dome lite .I found small 4a fuse out at fuse box(small one)but only get power to one side of clip,I am sure this must be my problem but how do you get power on other side of clip.I would appreciate any advice on troubleshooting tech.Thanks.Jerry  

idrivejunk idrivejunk
Addict | Posts: 5117 | Joined: 12/09
Posted: 12/14/12
05:58 PM

Have you taken the fusebox off the firewall and checked for rotted terminals on the backside? Common source of problems, easily solved by installing a modern blade-type fusebox. The metal instrument cluster housing needs to be grounded good too, and the area where the printed circuit connector goes can rust, causing problems.  
idrivejunk

chevelleman63 chevelleman63
New User | Posts: 21 | Joined: 11/11
Posted: 12/14/12
06:29 PM

I appreciate the quick response Idj,no have not taken box off fire wall ,they have worked before just lost connection ,rebuilding dash this last time out.I'll pull fuse box off & check other side hope I find problem,if not how much trouble to change out  box,not to sharp on electrical.I'll double check ground connection at cluster,feel like it's something real simple.Thanks for your help,I'll let you know what I found.  

idrivejunk idrivejunk
Addict | Posts: 5117 | Joined: 12/09
Posted: 12/14/12
06:53 PM

They make kits that are quite simple to install, its really just a matter of cutting the connectors off the old wires and plugging them into a different looking fusebox after replacing all the connectors. I've used one in a whole harness replacement and they are a great upgrade. If you find just one rusty piece back there, you may be able to make a new one to fix your trouble. Once I had half a fusebox rotted so I bought a cheapo six-hole, blade-type generic fusebox and was back on the road in less than an hour with my crimpers and a handful of connectors. If this gets very technical we may need more help though! I had a 72 SS once, boy was it a rustbucket.  
idrivejunk

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/14/12
07:44 PM

lets look at the dash cluster illumination circuit..

Sw144headlightswitch 1

see the green wire on terminal 2...

that leads to the short fuse in the fuse box.. from there is becomes a grey wire and leads all over the dash board....

the power for the dash cluster illumination circuit comes from the jumper on from PIN 4 to pin 3... and that is powered from pin 5... the tail light fuse...

the wire colors on your switch might be slightly different..


by the way... can you  check the ground wires to the various bulbs...  they are the black wire .. they seem to be grounded to 2 places...  i don't know where they are grounded at.. as i only have a wiring diagram...   also how is the negative battery cable to the body wire connected ..and do you have a braided ground strap from the back of the cylinder heads to the firewall??? is that properly connected...

i have a quick test if you have a digital volt meter and your engine runs....

post if you own a hand held digital volt meter...

i am looking at a 72 chevelle wiring diagram

A. is white.. to the dome light.. this grounds through the switch to complete the dome circuit.

1. is RED  power for the headlights..

2. is dark green..  to the illumination fuse...

3. is jumped to 4 as shown above..

4. is the tail and running lights.. Brown wire...

5. is red from the tail light fuse

6 is to the headlight dimmer and is LIght BLue... shown as yellow above...



so.... when you turn the headlights or parking lights on.. with a test light do you have any voltage on the short fuse in the fuse box?? check both fuse clips...  should vary when you rotate the knob...

if NOT... pull the short fuse out... the short fuse holder closest to the 4 fuses in a row might be the lamps side of the fuse... can you jump that for a split second with a wire and see if your dash lights come on full brightness????

this allows you to test the dash lights without pulling the headlight switch...

hope this helps....  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/14/12
08:10 PM

.I found small 4a fuse out at fuse box(small one)but only get power to one side of clip,I am sure this must be my problem but how do you get power on other side of clip.I would appreciate any advice on troubleshooting



DOH!!!

i missed it...

is the fuse blown????    use continuity beep or a test light ...

are the terminals that hold it corroded or rusty..

72 Chevelle Fuse Box  

chevelleman63 chevelleman63
New User | Posts: 21 | Joined: 11/11
Posted: 12/14/12
09:35 PM

Yes the 4a fuse is blown,and yes I did use a jumper at the fuse clip for just a second had no lights on dash with this test.I will have to find power at other end of clip.I will  take out fuse box to check back side for loose or bad wiring,appreciate your help will let you know how things turn out.  

chevelleman63 chevelleman63
New User | Posts: 21 | Joined: 11/11
Posted: 12/14/12
09:50 PM

OH!I really appreciate the info on the switch diagram and  the wiring layout,I definitely will need this to help trouble shoot this problem.
                 
         Jerry  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/15/12
01:51 AM

invest in a test light / circuit tester...  under 5 bucks at most stores..

pull the fuse...   turn the parking lights on.. probe the fuse clips... do you get power on one side... you should..

while hooked to the one side that gets light on the test light.. rotate the knob back and forth..  the test light bulb should change in brightness...

that verifies half the circuit.. the green wire from pin 2 on the headlight switch to the fuse block is good...

i don't recall what the 4 amp fuse number is.. its stamped lightly around the caps on the fuse..


AGA Fuses
1/4" X 5/8", Ratings from1/16 to 30 amps.

AGW Fuses
1/4" X 7/8", Ratings from 1 to 30 amps.

AGC Fuses
1/4" X 1 1/4", Ratings from 1/20 to 30 amps.

SFE Fuses
Size rejecting 1/4" diameter X length: 5/8 (4 amp). 3/4" (6 amp), 7/8" (7.5 amp), 1" (9 amp), 1 1/16" (14 amp), 1 1/4" (20 amp), 1 7/16" (30 amp).

its more than likely a SFE-4..  as after i looked at the AGA file.. they don't make one in 4 amp..

both would be 5/8" long..

2M3jbpfih7lk6q~~ 35  

idrivejunk idrivejunk
Addict | Posts: 5117 | Joined: 12/09
Posted: 12/15/12
07:36 AM

Back of the fusebox looks like this. One of those thin pieces of metal may be bad.

IMG 7156

Front: (I already had these pics posted for another thread and ran across them looking for pics for yet another thread) You should have power at the top and bottom of the fuse clamp on the hot side. This is a 69 Grand Prix but its similar.

IMG 7151  
idrivejunk

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/15/12
08:14 AM

wow... idj.. great pictures..

you can even see the Green and the Grey wires i was talking about...

IMG 7156  

chevelleman63 chevelleman63
New User | Posts: 21 | Joined: 11/11
Posted: 12/15/12
03:21 PM

The fuse i had installed was marked on the cap was a sfe-4A.I assumed this was a 4 amp fuse but it blew,I am looking for info on correct amp fuse that goes in this spot.I have found a 301 ag 20A fuse but could be to big and make matters worse.I hope someone can look in there fuse box and get back to me ,would really appreciate
it,I am determined on getting these dash lites going.Thanks Confused  

idrivejunk idrivejunk
Addict | Posts: 5117 | Joined: 12/09
Posted: 12/15/12
04:30 PM

SFE-4 is the correct fuse, but the reason fuses blow is because theres a short in the circuit. Thats what I'd look for. A bad wire or incorrect connection.  
idrivejunk

idrivejunk idrivejunk
Addict | Posts: 5117 | Joined: 12/09
Posted: 12/15/12
04:36 PM

Heres a 71 Cutlass diagram, should be real similar. Now is when you gotta get out your test light or meter and be a mechanic. Have a good look at the cluster housing where the printed curcuit connects because if theres damaged paint or rust there, she will blow every 4A fuse in town.

71Cutlasswiring  
idrivejunk

Dave632 Dave632
Addict | Posts: 2219 | Joined: 07/08
Posted: 12/15/12
06:32 PM

I would look for anything that looks like it has been worked on.
I have found that most guys who work on cars have no clue about electronics.
I spent over 30 years as an electronics technician and found many problems caused by others working on a problem usually causing more problems than they started with.
If you have an ohm meter start checking resistance and see where it is least and work your way back from there. If resistance starts to increase you are going away from the trouble.  
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