Fuse Panel Replacement?

[Drewfrazier]

I am bringing my new old '72 K5 into the 21st Century (but only barely) and am having some minor electrical issues. Turn signals (outside and the dash panel indicator) only work to the left, fan motor inop and the new tach I just installed (connects to unfused ground and Tach connector on HEI distributor) doesn't budge when I fire it up. (The kit, from Brothers, suggests compatibility with most HEI systems.) Looking at the fuse box, below, with all that corrosion, I think the obvious first move is to replace that. Other guages (Fuel, Water Temp and Oil Pressure) are working although the Ammeter is awfully quiet. Anybody tackled replacing the fuse box? Thoughts? Thanks, guys!

 

[6872xtc]

I can't think of where to start on the right turn signal, except check the dash bulb and check for power at the front socket. Have you tried the 4 way flashers? I wonder about the connector where the turn signal switch plugs into the main harness too.

The fan motor can be several things. Check that it's plugged in and has a ground wire. Check that the fuse is good and putting power to the tabs of the fuse holder. Emery cloth can probably clean them enough to work, but may be only a temporary fix. Some kind of chemical or mechanical cleaning is needed, then I would use a little dielectric grease to help keep the corrosion away.

I have a reproduction tach that worked fine with HEI and is now running with MSD ignition. The note that they say about HEI is the reproduction wire terminal is incorrect. Check the wiring as I thought that it needed power, ground and signal from tach output of ignition.

The ammeter could possibly be one of the small fuses in the corners of the front fender to radiator support corner. Look for small, rubber bullet style connectors. Pull them apart and check the 2 amp fuses. They are protection for the ammeter shunt circuit.

You can change the fuse panel and main harness easy enough in a day, in my experience, but it may not cure all of your problems.

 

[bp71k5]

Yea, figure out what’s wrong before replacing the fuse panel. I’ve done it, not too hard if everything was working when you removed all the wiring. That way of something doesn’t work afterwards, it’s your fault.

 

[diesel4me]

I've had 4 GM trucks in the 70-72 year range ,none had fuse box issues,other than one having the connections where the two halves bolt together at the firewall--I unbolted it and sprayed some white vinegar on the connectors and let it sit awhile,then sprayed it off with electrical contact cleaner...when I put it back together,my dash lights now worked and were brighter..

If you had a leaking windshield at the corner that let water get in the fuse box,then it might be corroded enough inside to cause problems,but usually the fuse box gets dried out rather quickly by the wind and warm air from the heater and doesn't stay wet long enough to be an issue,until the truck sits idle a long time..

One wire I had issues with on the truck with the corroded fuse box was the tan wire that gives 12V to the alternator to energize the field windings and make it charge--it often refused to charge until I got out and jumped the wires on the 2 prong plug on the alternator..
I later found that wire was just green powder inside from the fuse box to about 6" towards the engine..replaced it and had no more trouble..

I've had newer fuse boxes with the ATC blade fuses give more trouble than the old glass style fuses as far as the tabs on the fuses getting corroded and making things stop working..

 

[Drewfrazier]

I have a reproduction tach that worked fine with HEI and is now running with MSD ignition. The note that they say about HEI is the reproduction wire terminal is incorrect. Check the wiring as I thought that it needed power, ground and signal from tach output of ignition.

Thanks for the very thorough response! Could you expand on the HEI tachometer note and how to fix it? My kit came with only two external wires; one went into the Tach connection on the distributor and the other into unfused (ground?) on the fuse box.

 

[6872xtc]

The unfused terminal at the fuse panel is power, not ground. You will have to verify that it actually has power and hasn't lost connection somewhere. Test light or multi-meter.

 

[Drewfrazier]

I can't think of where to start on the right turn signal, except check the dash bulb and check for power at the front socket. Have you tried the 4 way flashers? I wonder about the connector where the turn signal switch plugs into the main harness too.

The 4-way flashers fired all corners. Thanks for the tip! Some new bulbs later it worked.

 

[Drewfrazier]

The unfused terminal at the fuse panel is power, not ground. You will have to verify that it actually has power and hasn't lost connection somewhere. Test light or multi-meter.

Reply: I've got a multimeter but not sure what to connect to. I assume, with key on but motor not running, touch positive to either pole of an (intact) fuse and the negative to some bare (not painted?) metal? Like a fuse panel mounting bolt?

 

[6872xtc]

Reply: I've got a multimeter but not sure what to connect to. I assume, with key on but motor not running, touch positive to either pole of an (intact) fuse and the negative to some bare (not painted?) metal? Like a fuse panel mounting bolt?

Yes. I would try to scuff some bare metal for the negative lead to touch. The rust can be more of a barrier to electric conductivity than a person thinks. You can use the tip of the probe to scratch through sometimes.
And corrosion on the fuse terminals can mess with meter readings as well when you are checking to see if power is getting through a fuse to the fuse box terminals. Just because there is power going through a fuse, doesn't mean that the terminals are making connection to the fuse.