1 ... 35 36 37
TurnerX19
TurnerX19 UltraDork
11/27/21 9:57 p.m.

I seem to remember a Lucas alternator that would not charge if the bulb burned out. Check your output first thing when you start up to be sure yours is going to charge without the bulb.

JoeTR6
JoeTR6 Dork
11/27/21 10:17 p.m.

The Megasquirt is showing 14 volts and the gauge 14.7, so it appears to be charging.  Also, I'm using a 1980 Ford Fiesta alternator that uses the same mount and plug as a TR6.  There's a third brown wire going to the alternator to power the field coil on startup.

But I believe that Lucas would do such a thing.

JoeTR6
JoeTR6 Dork
11/28/21 2:46 p.m.

Just one more thing and I'll shut up for a while.  Something I noticed yesterday was that the turn signal indicator was only working to the right.  I forgot that the way it works, current flows either direction through the indicator bulb depending on turn direction.  That doesn't work so well with LEDs (which the new speedometer has), so I put together a diode bridge rectifier and soldered it in.  Works great now.  While I was under there, the brake warning bulb had failed, so that got replaced.  Doing so also restored the oil pressure warning light as they are wired in series.  Low oil pressure lights up both to really get your attention.

JoeTR6
JoeTR6 Dork
11/29/21 8:53 p.m.

Firstly, I need to apologize to TurnerX19.  The TR6 is indeed not charging without that bulb.  I could have sworn I checked it and even had a data log, but that must have been with the lamp in place.  It's pretty awful that if that lamp burns out, it causes the battery to not charge while failing at it's one task of letting you know.  So with the bulb replaced, I figured out that running the vent blower drops voltage enough to shutoff the car.  That's certainly not a good long-term solution.

In other news, I'm now searching for a sporadic coolant leak.  When it happens, it starts dripping coolant fairly quickly under the radiator.  But then it will stop and can't be reproduced.  It's like quantum physics where observing the leak causes it to not happen.  Good thing winter is coming.  I need some time off.

TurnerX19
TurnerX19 UltraDork
11/29/21 11:03 p.m.

In reply to JoeTR6 :

Lucas is not the only alternator to require a functional bulb, but it is the one I saw the most failures on. Only Lucas could make bulbs that bad back then. Now I am not sure they are the worst! Please go Japanese or Bosch, or even GM, they work far longer. Most newer units, especially the one wire ones do not need the bulb.

JoeTR6
JoeTR6 Dork
11/30/21 3:54 p.m.

In attempting to fix the run-on issue, I tried using an LED with a resistor so that it could withstand 12 volts.  That does indeed block current from reaching the ignition switch, but drops the voltage too much (down to 10.8 volts) at the alternator on startup.  Since I don't need the light, maybe what I need is just a diode.

TurnerX19
TurnerX19 UltraDork
12/1/21 11:46 a.m.

Plus 1 on the diode. There have been cars of non remembered make that had just such a thing from new. They would run on when the diode failed. 

JoeTR6
JoeTR6 Dork
12/1/21 1:30 p.m.
TurnerX19 said:

Plus 1 on the diode. There have been cars of non remembered make that had just such a thing from new. They would run on when the diode failed. 

I soldered a diode into a lamp base this morning and it worked.  The only diode I had was just 1 amp max, so I should measure the alternator excitation current before declaring victory and order a pack of 5A low forward voltage drop diodes.  Edit: The alternator is drawing 3 amps with just the key on.

The other thing was jacking up the car to look for the coolant leak.  It appears to be coming from the lower radiator hose, so those connections were tightened.  There was a dried coolant trace coming down the radiator, but that could easily have been a spill from topping it off.  Or cheap Chinese aluminum radiator, so I'm keeping an eye on it.

1 ... 35 36 37
Our Preferred Partners
jpqPryFVvqz37WP9EmOEYAJympABcsHP31cwJe5TtbUic11IoeE0adez435B77mF