74 620 Problems: Ignition Switch & Intermittent Headlights

[Cardinal Grammeter]

Problems are coming out of the woodwork about 1.5 years after I started driving my 620:

 

• Ignition Switch:  To Start, I have to turn all the way to the stop and then back off a little to get the contacts to work.  But the real question is could the ignition switch be responsible for the engine shutting off when driving.  It has done this maybe 3 times.  I pull off the road and stop.  Then ignition off, then start again and everything works.
• Headlights:  Low's go out intermittently:  If I cycle the dimmer lever, maybe 1 out of 10 times, there are no Lows - another cycle and they work.  I had one instance when starting truck there were no headlights at all.  I cycled headlight switch and dimmer and eventually they came on and worked.  Also, most recently had no lows after startup.  Cycled the crap out of dimmer and finally got lows.  I just R&R'd the head light relay spade terminals just in case - they are probably corroded...
  
  One test I did was to turn headlights off while no lows and then turn on:  the lows came on.  Since Dimmer was not touched, the only thing that moved was the relay.  I don't think corroded dimmer contacts are the issue - I'm betting relay. 

 

When I bot this truck it was evident that it sat for a long time - it wouldn't surprise me for 10-20 years.  I had/have other electrical issues:

 

• The fuse box had to be soaked in vinegar to get conductivity and throughput.
• The Windshield Washer Switch had to be disassembled and the copper block contacts had to be polished - they were green/blue withe heavy corrosion.
• Lost the body ground and burned out the black alternator regulator wire.  This was fixed.  I don't think it has any bearing on current problems.
• Dash lights flicker probably due to bad instrument voltage regulator.

 

Are these problems typical or am I facing something more systemic?

 

Thanks in advance,

Tom

 

 

 

 

 

[datzenmike]

Headlight relay.

 

The relay can only be high beams or low beams, there's no in between. No headlights at all, it will be the fuse or the fuse contacts. Possibly the headlight switch.

 

When the relay is OFF the default position is high beams.

 

You MUST have parking lights working to select low beams. The dimmer switch provides a path to ground for the parking light power through the headlight relay, which energizes it, and sets it to low beams. No low beams.... the relay stays in the default position of high beams. OR if parking lights working the dimmer switch ground is faulty or relay is bad.

 

Ignition swtch

 

If acting odd when shutting off I'd replace it. Random shut off while driving is dangerous enough. Sometimes when starting, my engine turns over excessively but when I release the key boom it fires up.  The switch connects the ignition and the starter separately. Seems like the key goes to far right and only the starter is powered. Now I turn the key slowly till the starter engages and not full against the stop.

 

 

Instrument (dash) lights.

 

There is no voltage regulator for the dash lights. It's connected to the parking light fuse. Flickering is something loose. Do the parking lights flicker? If no it's something loose in the dash. Try turning the dash dimmer rheostat multiple times to clean the contacts. If yes then headlight switch or wiring or the fuse powering them.

[Cardinal Grammeter]

1 hour ago, datzenmike said:

Headlight relay.

 

The relay can only be high beams or low beams, there's no in between. No headlights at all, it will be the fuse or the fuse contacts. Possibly the headlight switch.

 

That makes sense to me.  This happened only once so hard to diagnose.  Fact I had to vinegar the fuse block does not instill confidence nor the level or corrosion muck on the wiper switch.  If the headlight switch is made similar to the wiper switch, it probably should be disassembled, cleaned and polished.

 

1 hour ago, datzenmike said:

 

When the relay is OFF the default position is high beams.

 

You MUST have parking lights working to select low beams. The dimmer switch provides a path to ground for the parking light power through the headlight relay, which energizes it, and sets it to low beams. No low beams.... the relay stays in the default position of high beams. OR if parking lights working the dimmer switch ground is faulty or relay is bad.

 

If the default position is High Beams, IF the relay did not actuate, wouldn't I ahve High Beams no matter what Dimmer position?  The intermittent is NO Low when in Low Dimmer - High Beams seem to work always.

 

1 hour ago, datzenmike said:

 

Ignition swtch

 

If acting odd when shutting off I'd replace it. Random shut off while driving is dangerous enough. Sometimes when starting, my engine turns over excessively but when I release the key boom it fires up.  The switch connects the ignition and the starter separately. Seems like the key goes to far right and only the starter is powered. Now I turn the key slowly till the starter engages and not full against the stop.

 

Ignition switch definitely given to wonky behavior give your experience too.  Lifetime from AutoZone.  CHOICE:  $24 Duralast or $30 Locksmart, both w/key.  Which to get?????....

 

1 hour ago, datzenmike said:

 

Instrument (dash) lights.

 

There is no voltage regulator for the dash lights. It's connected to the parking light fuse. Flickering is something loose. Do the parking lights flicker? If no it's something loose in the dash. Try turning the dash dimmer rheostat multiple times to clean the contacts. If yes then headlight switch or wiring or the fuse powering them.

 

Hard to tell if parking lights flicker when driving - they don't when stopped - I'll have to check if dash lights flicker when stopped...  NOTE:  when I saw flicker, I don't mean they're going on and off, it's more like voltage flickering 20%.

 

My Dash Dimmer DOES NOT effect the instrument clusters, only the Wiper Switch Illumination and the Radio.  

 

Isn't there an 8v regulator for the dash instruments?  I have the problem that Temp and Fuel both increase when I have Parking or Headlights on.  Since there is no difference in the increased whether Parking or Headlights, it is not related to the current difference between them.  However, I suspect it might be due to the current of the dash illumination lights.  

 

QUESTION:  Why are the dash lights so dim?  Did they have plastic color filters that turned yellow like headlight lenses?

[datzenmike]

20 minutes ago, Cardinal Grammeter said:

 

 

If the default position is High Beams, IF the relay did not actuate, wouldn't I ahve High Beams no matter what Dimmer position?  The intermittent is NO Low when in Low Dimmer - High Beams seem to work always.

 

 

In operation the relay is in the high beam position with the headlamps off. When you turn the parking lights on or all the way to headlights (also with parking lights on) the relay immediately clicks to low beams IF the dimmer switch is set to low beams.

 

29 minutes ago, Cardinal Grammeter said:

 

 

Hard to tell if parking lights flicker when driving - they don't when stopped - I'll have to check if dash lights flicker when stopped...  NOTE:  when I saw flicker, I don't mean they're going on and off, it's more like voltage flickering 20%.

 

My Dash Dimmer DOES NOT effect the instrument clusters, only the Wiper Switch Illumination and the Radio.  

 

Isn't there an 8v regulator for the dash instruments?  I have the problem that Temp and Fuel both increase when I have Parking or Headlights on.  Since there is no difference in the increased whether Parking or Headlights, it is not related to the current difference between them.  However, I suspect it might be due to the current of the dash illumination lights.  

 

QUESTION:  Why are the dash lights so dim?  Did they have plastic color filters that turned yellow like headlight lenses?

 

I did not know this but dash lights are non dim-able until '76. Your '74 have full 12 volts at all times. Only the heater controls, wiper dim. For the dash lights get brighter LED 'bulbs'. The '76 also included a head light switch know that was dim-able. Take the dash gauges out and they have blue colored covers on them, at least my '78 did. I scratched some of the covering off to make them brighter.

 

The 8v regulator was only for powering the temperature and fuel gauges, nothing more.