’78 International Harvester Scout 2 – Part 5 Electronic Ghosts and the Road-map for the future

In international harvester, project truck, scout, troubleshooting on January 12, 2015 at 3:02 am

Originally I had planned to attempt building a rear bumper for the Scout today.  However, since I don’t need the bumper to get the truck through the emissions test and licensing, I decided that maybe I was getting ahead of myself.  I decided that I would work on some miscellaneous electrical problems.  The first was a mysterious drain on the battery causing it die if I left it hooked up over night.  The second was my turn signals not working.  The third was dash/gauge lighting that was very very very dim.

I thought that I had a short somewhere that was causing the battery to die.  But while working on the timing I touched a wire (insulated) that was really hot.  It turns out that this is a resistance wire that is supposed to be hot.  But only when the truck is running.  After further research I discovered is supposed to run to an ignition switched power source.  This means that it shouldn’t be getting power unless the truck is running (or the key is turned over so accessories like the radio work).  Mine was hooked to an always on source.  This meant that the alternator was draining some of that power but also the wire (being a resistance wire) was taking a lot of that power and turning it into heat. While disconnecting the wire from the current power source I discovered that it was in really bad shape and the insulation was flaking off.  This type of wire is a pretty big fire hazard without insulation on it so it needed to be replaced.  Apparently nobody sells the plug with the two wires for the alternator that includes a resistance wire.  My cousin suggested that I just use a regular wire with an in-line resistor.  I got on-line and checked some message boards and found that the in-line resistor is the standard work around.  So I ordered a 50w 15ohm resistor from Mouser Electronics.  When it arrives I will get it wired up to a switch source, probably the cigar lighter.  As a side note, you know you are working on an old vehicle when the lighter is called a cigar lighter rather than a cigarette lighter or power plug.

The second problem was the turn signals.  The hazard lights worked so the connections at the bulbs must be good.  I swapped the hazard and turn signal relays around and the problem stayed with the turn signals so the relay is good.  I concluded that it must be the turn signal switch that is the problem.  Unfortunately that is a really hard switch to get too.  I need to remove the turn signal lever, the tilt steering lever, the ignition switch (where you put the key), and the steering wheel before I can remove the cover on the top of the steering column and get to the turn signal switch.  I don’t own a steering wheel removal tool (although I could probably fabricate one) and I don’t know how to remove the ignition switch.  While investigating the problem I must have bumped the right thing because the turn signals started working on their own.  At some point I need to open it up and fix the problem but for now I am going to ignore it and hope for the best.  I can always use hand gestures to signal turns if need be.

The third problem was the gauge lights.  The wiring for the gauges is a mess.  The power for the gauges themselves runs in series.  The power for the gauge lights run in their own separate series and the inputs for the gauges come in as a mix of mechanical and electrical and vacuum inputs.

The wiring on the back of the gauge cluster.  The lights are wired in series as is the gauges themselves with seperate inputs for each gauge.

The wiring on the back of the gauge cluster. The lights are wired in series as are the gauges themselves with separate inputs for each gauge.

This gauge has the light wired in series.  You can see the wire come from the light on one side go through the light fixture (the large black plug) and then go out the other side.

This gauge has the light wired in series. You can see the wire come from the light on the right side, go through the light fixture (the large black plug) and then go out the photo to the left side.

My guess is that the lights are dim because one or more of the connections between them is bad so that only a small part of the electricity is able to flow through the circuit.  The connections are made with insulated butt joint connectors.  You can see one of these in the photo above.  It is a see-through pink color.  The problem with testing these is that they are kind of a pain to get the multi-meter probes on.  The easiest way is to remove the light bulbs and put the probes on the correct spots within the plug to test the path from one light to the next.  This would allow me to find any bad connections.  The second option is to wire the light from each gauge to the gauge power and ground.  This removes one series from equation.  Each gauge is wired in series with the lights connected to the gauge power and ground.  The speedometer and tachometer are the exception to this rule.  They don’t have gauge power and so the lights will probably be connected to the neighboring gauges.

This gauge has the light wired to gauge power and ground rather than in series with the other lights.

This gauge has the light wired to gauge power and ground rather than in series with the other lights.

This solution looks neater and is easier to troubleshoot and find any potential issues with the wiring.  The negative is that the gauge lights will always be on if the Scout is running.  This means that you don’t have an in-dash indicator showing you that the headlights are on.  I have one extra indicator light on the dash that I can use for this.  Originally it was to be used to indicate if the truck was in 4 wheel drive but I think I would rather have the headlight indicator.  I could use the “bright” indicator as well but I like being reminded if my high beams are on so I would rather not re-purpose that indicator.

At the end of the day nothing was really fixed but I have a handle on two of the problems and the signals are working for the moment so we will call that a victory as well, albeit probably a short-lived one.  I will probably rewire the gauges over the next couple of days as well as fix the alternator wire/resistor when the resistor arrives.  I ordered a new gasket for the water pump yesterday.  It should arrive on Tuesday.  Fixing that leak will be the next project.  I need to remove all the radiators and the rest of the air conditioning equipment to let me get at the water pump.  This will let me see what condition the radiator and transmission coolers are in.  The radiator had a large leak that has been temporarily fixed with an fluid additive.  I will probably try and replace it during this next project.  As long as I have it out and the fluid drained it may as well be done.  I will also be able to clean the front of the motor.  You could see how bad the grease was in the photo of the tab with the timing marks on it in the last blog.

Tonight I ordered new gaskets for the motor and the differentials.  I might replace the motor gaskets while I have the front opened up and all of the radiator hoses out of the way.  I have a large vacuum leak that I think is from the drivers side head cover gasket.  Hopefully the new gaskets will get rid of that leak and any others.  This should let me finish the idle tuning.  If it does the truck will be ready for emissions testing.

I still need to get gaskets for the transfer case as well as get a new gear for the speedometer.  Since that sits between the rear drive shaft and the transfer case I will probably tackle both of those at the same time.  It would be nice to have a speedometer that indicates the correct speed.  Right now I use my GPS navigation to see how fast I am driving.  I guess that is it for now.  Don’t expect another blog on the Scout until I have a chance to do some real damage while fixing the water pump.  Until then…


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