Not My Day! Electrical Issue Help Request

[trguy75]

It must be that my Land Rover does not want to leave home. I am getting ready for her to go to a new home and she is acting up like she wants to stay. The truck ran great! First the carb problem this morning. See earlier thread. Now the headlights flickered and then stopped completely when checking them. Fuses good. Next, I removed the dash panel to check the switch and changed out for another one just to eliminate that being a problem. Still didn't work and now the heater blower, running lights, blinkers, wipers, fuel and temp gauges do not work. I must have shorted something out.

Fuses still good. Truck starts up and runs. Choke light works, horn works, interior ceiling light works. I have reviewed the wiring diagram. I have a 68 Series IIA USA spec negative ground. Seems like it might be the voltage regulator in the engine bay and/or the voltage stabilizer mounted to interior side of firewall behind dash panel. Any thoughts. The voltage regulator looks just like my Lucas one from my Triumph TR4.

Thanks in advance,
Jim

[trguy75]

Diagnosed some of the electrical to a bad voltage stabilizer. The good news is that it is identical to my Triumph TR6 and I had a spare that worked. All electricals back in working order except headlights and running lights. Now diagnosing headlight switch and that circuit. Turns out my voltage regulator was gutted in the conversion to an alternator so it wasn't that part. Jim

[SafeAirOne]

Well, as you probably know, if you're down to only the head and parking lamps not working, then troubleshooting will be pretty easy with a multimeter.

How'd you make out?

[triumphtr7guy]

Ah the demons of Lucas!!! at least you have a TR6 to balance off your Lucas diagnosis ability!! thank goodness for parts-bin engineering and cars of the same vintage having a LOT of similar electiracls parts. Try pulling the connecors off the switch and reattaching., maybe a little contact cleaner for good measure. Try running a jumper from the hot side of the battery to the headlight high or low spade on the bulb and see if things light up, just to make sure the bulbs are good. I would try woking back from the bulbs to the switch with the meter and see where things drop off. Could be corrosion, loose, who knows what you will find.
good luck Jim

Bruce Penttinen 73 Series III and TR7's,. multiple!

[tkneese]

I'd like to know what you find is wrong because my headlights went out too. i know the bulbs and fuses are fine and i replaced the dimmer switch thinking that may be the issue but that didnt fix it. I'm a little hesitant to mess with the panel switch and the parking lights work when turned half way on so i'm a little confused.

[Jdnewberry]

I'm not sure if you've checked this yet or not, but when I picked up my SIII last summer, it's headlight issue turned out to be a loose ground wire. Symptoms were very similar, except for the fact that my right turn signal would glow dimly.

As stated earlier, I would grab the multimeter and work back from the lights. If you have voltage at the bulb, trace the ground.

Good luck!

[chuckstp]

The best way to solve these kind of problems is to divide and conquer. You can test most of these components independently of each other which saves a good deal of guessing. To test the headlights without the switching circuit, remove the wire from the headlamp from the back of the switch. Then connect that wire into the positive terminal of the inspection socket. If the lamps light, then your problem is with the switch or its wiring. If they fail to light, then your issue with with the lamp or its wiring. To isolate the wiring harness from the bulb and its ground, disconnect the wire closest to the headlamp. Run a jumper to the positive of the battery terminal.

I've had to troubleshoot a large variety of electrical circuits from PC boards w/ surface mount components to telephone power supplies. The Land Rover wiring is one of the easiest I've had to troubleshoot simply because it is so easy to isolate most things from the circuit. That assumes the connectors come apart. When they don't come apart, that is often where the trouble lies.

[o2batsea]

99 times out of 100 it can be traced to a bad connection. Usually a ground. Highly unlikely it is the VR or the stabilizer. Stabilizer only serves a couple gauges.

[tkneese]

welp... after cleaning all the grounds, connectors, replacing the dimmer switch to no success... i traced all the wires in and out of the dash... and found one of the connectors was disconnected near the fuel pump that leads to the dimmer switch. plugged her in and all was right in my world again.

[trguy75]

Sorry for the delay in response. I am working too much. Turns out the contacts on the fuse box were not completing the circuit across the fuses. Fuses were good but no juice on one side of the fuse link. Turns out that was the link that powered the heater, oil pressure gauge (aftermarket electric), blinkers etc. The voltage regulator ended up being good after all. Headlights are working after swapping out another light switch. The aftermarket ones don't seem to be as good as the originals. All is working now on the electrics. Thanks for the responses.

[o2batsea]

Yeh amazing that there's only one fuse in the entire electrical system, right? As you know British fuses are rated at the ampereage that they will immediately blow. USA (Buss) fuses are rated at the max amperage they can carry for a period of time before blowing.

reposting:
Automotive Electrical Fuses -- British Vs American (Tim Engel’s opinions – use at your own discretion)
British and American standards for rating electrical fuses are different. Both provide an “Amp
Rating” for very similar looking fuses, but the two ratings mean very different things. The US
system rates the fuse based on the continuous load it can handle for a specified period of time w/o
blowing, whilst the British system expresses the load at which the fuse will immediately blow.
That’s a significant difference! As an example, the 35 Amp fuse called out for many 1950’s/ 60’s/
70’s vintage Britcars (Lotus Elan & Europa for sure) is roughly equivalent to a US-spec BUSS
AGC 17 Amp fuse. Install a US 35 Amp fuse into your LBC fuse box and the wiring harness will
melt down before the fuse blows.
DO NOT use a USA rated 35 amp fuse in your vintage British car!
The complete rating for the specified 35 amp Lucas fuse is…
“17 AMPS CONTINUOUS / 35 AMP SURGE”
Early British fuses were simply marked with the quick-blow rating, but later fuses are given two
ratings in an effort to minimize the confusion. For instance, the 35 Amp fuse is often marked as
“17 continuous/ 35 blow”, or simply 17/35. In that case, use the lower “continuous” rating as the
one to which you try to match an American BUSS fuse rating. Or, better yet, proper British fuses
are available from your favorite independent Britcar / Lotus parts dealer. Purchase a supply and
keep them in your Lotus' glove box.
The comparison/ substitution looks something like this...
British Lucas Fuse ~ American BUSS Fuse
Fast Blow Dual Rating ~ Continuous (AGC) Alternate Opinion (SFE ?)
50 amp 25/50 amp ~ 25 amp 25 amp SFE
35 amp 17/35 amp ~ 17 amp 20 amp SFE
30 amp 15/30 amp ~ 15 amp 15 amp SFE (too short ?)
25 amp 12/25 amp ~ 12 amp 15 amp SFE (too short ?)
20 amp 10/20 amp ~ 10 amp
15 amp 7.5/15 amp ~ 8 amp
10 amp 5 /10 amp ~ 5 amp
5 amp 2.5 / 5 amp ~ _____ 3 amp
2 amp 1 / 2 amp ~ 1 amp
Unfortunately, there’s no extra data marked on either the fuse body or on the package to tip-off
the user that the ratings are different. It’s very important that USA owners of British cars be aware
of the issue and make wise choices when using USA fuses in them. The best choice is to make
the effort to source proper British fuses for your LBC. In an emergency, the loose Rule of Thumb
is to use a USA BUSS fuse with an Amp rating equal to no more than one half of the British
Lucas fuse rating.