Problems with headlights and signal lights

[inaminit]

Steve-85 should be near zero ohms to ground. Try the push pin test between the point near the plug to a push pin near the ground lug on the wire, lug off the post. Then push pin at plug to the lug, then lug on the post, probe on the post. Also see what the post measures to bat neg. Also clean the ground lugs on the outside of the battery boxes and pull the headlight bulbs, and test 87 and 87a to the headlight lug sockets. You seem to have a high resistance somewhere.

[sballard]

If I touch to two probes attached to my multifunction meter together, I get 0.1 ohm. If I use the push pins to contact the one of the 2 ground wires near the headlight flasher plug and one of the three ground wires connected to the lug, I get 0.4 ohms. I get this same reading with each of the 2 ground wires near the lug, but the other wire is just in too tight a spot to get a measurement.

Am I supposed to get "0.0 ohm" reading or is the value I get (0.4 ohm) too high?

[inaminit]

I do not know-a quick check in one reference indicates wires do have a finite resistance-but measured in milliohms. If your meter won't zero with the probes together-buy a cheap analog with a thumbwheel-that is what I have been using lately. You can adjust it to zero.
Why don't you regroup, have a beer and finish off today by wire brush cleaning all fuses and ground posts, coating all cleaned surfaces with dielectric grease. Study the diagrams and trace power in from bat plus to switches to relays and fuses, and through to the lights. Take a look at a 74 current flow diagram-it helps to understand how stuff functions.
Then remove the light switch and map the terminal numbers and wire colors.
Next-measure volts at terminal 30, key off, and term 75 key on.
Then, using the diagram-chase down the voltage to parking, low and high beams, then do turn signals.

[sballard]

I just went back and sanded down every wire connector and washer that attaches to the lug. I got the resistance between the ground wire of the headlight flasher plug and the ground lug wires down to 0.2 ohm. I know the resistance is still not 0.0 ohm, but with the resistance of the meter probes alone as 0.1 ohm, is this resistance low enough?

[inaminit]

Also-just for fun-open the door and put a known good relay in the hi/low relay socket. Keep a finger pressed against the relay and turn on the key to on. Then pull the light switch to on (all the way out)
and the relay should click. Then operate the hi/lo switch-the relay should click each time.

[sballard]

Thanks for trying to cheer me up! But right now, the only thing that is really going to make me happy is getting this electrical problem sorted.

Looks like I need a multimeter that allows me to measure milliohm resistances.

[inaminit]

Steve- I have been working through similar problems on a 71 for a month now. I read sections of "European Automotive Electrical Systems" sold by our host, and I pored over the diagrams, and on Friday I had a big breakthrough. If I did it-anyone can. But you have to begin with an understanding of the diagrams. You really have to put that time in to make real progress. Then you can devise voltage and resistance tests to find problems as you work through the circuits.

[SpyderMike]

Steve,

At 0.1 Ohms resistance, did you try the turn signals? I don't think you need to worry about a lower reading.

Mike

[sballard]

SpyderMike- No I didn't try the turn signals, but I will tomorrow morning and see.

inaminit- I will take a look at that manual. My knowledge of electronics could stand to be improved! But I am learning a lot from this experience.

My thanks to all you guys that have helped me so far.

[SpyderMike]

You are doing great Steve.

The point I am trying to make is that the relay needs a good ground to be able to switch.

[inaminit]

Don't forget to clean the 2 ground posts and lugs on the back sides of the battery boxes.

[sballard]

I cleaned up the ground posts on the battery boxes this morning but it did not make a difference.

I ordered new headlight flasher changeover and direction warning blinker indicator relays to see if the problem lies there. Fortunately, they aren't very expensive. They should come in tomorrow.

[sballard]

Oye....

I plugged in the two new relays and .....

Good news - the blinkers work!

Bad news - now my high beams don't work!

For those who may not be familiar with my previous tale of woe, I lost my high beams a couple of months ago and I went through a similar saga to get this fixed. Many thanks to SpyderMike to help me get this working. Here is the thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/978852-problems-headlights-signal-lights.html

The fix required taking the Headlight flasher changeover relay out, gutting the internal electrics, and soldering in a jumper wire between the "30" and the "87a" post. Unfortunately, as I learned today, this also took out the turn signals too.

So....I guess I am back to my original problem. How do I repair the high beam lights?

When I was dealing the the high beam issue before, I actually ordered a new complete Turn Signal assembly ($$$) which I did not use because I thought we had the problem sorted out by the time that the part arrived. Maybe it would be worth putting it in. Right now, I don't know of anything else to try.

Anyone out there like to chyme in with suggestions?

[SpyderMike]

Steve, please leave the new flasher relay in and put your old modified hi/lo changeover relay back in (after removing the new one you just installed) and tell us how things work.

There should be no connection between your mod of the changeover relay and your turn signals.

[sballard]

I've already done that. The high beams work but the turn signals don't.

[SpyderMike]

Ok, I didn't gather that by what you posted. So the new relays really didn't do anything different. Your old relays had the same effect, correct?

Have you tried everything these configurations:

No changeover relay at all (empty socket) and old relay for flasher?

No changeover relay at all (empty socket) and new relay for flasher?

How do hi/lo beams work and turns signals work in each of those configurations?

[inaminit]

Can we do some simple tests? From memory, based on my work yesterday on a 71, which has some elements of a 74 in the underdash wiring.
1. Key on, light switch off. New relay and flasher in. Hold finger on relay and turn switch to first position. Relay should click closed. Then pull switch to position 2. Relay should click open.
2. Then shut off switch, pull relay out far enough to touch posts with probes. Should be no volts at any post. Pull switch to first position, relay should click closed, 86 should be hot.
3. Pull switch to second position, relay should open, and either 87 or 87a should be hot, operate hi/lo switch-87a or 87 should be hot alternately.

[SpyderMike]

inaminit,

We have already gone through some basics...you might want to read starting back around post 51. The changeover relay is being fed a constant trigger on the white/green wires because it is being powered by the light switch at connection 57. His schematic seems to have a fault there.

In my mind, it should be powered by teh yellow wire coming off the turn signal switch at 56.

Mike

[sballard]

SpyderMike-

Just to make sure that I have my nomenclature correct - From the wiring schematic:

The relay for the turn signals is the "direction warning blinker indicator."

The relay for the high/low beams is the "headlight flasher changeover relay."

With the "direction warning blinker indicator" removed and the "OLD" modified headlight flasher changeover relay installed, the high and low beams work but the turn signals do not.

With the "direction warning blinker indicator" removed and the "NEW" headlight flasher changeover relay installed, low beams work but neither high beams nor turn signals work.

[SpyderMike]

Okay, and in post 136 I am suggesting you try this and report outcomes:

1. No headlight flasher changeover relay at all (empty socket) and old relay for direction warning blinker indicator.

2. No headlight flasher changeover relay at all (empty socket) and new relay for direction warning blinker indicator.

How do hi/lo beams work and turns signals work in each of those configurations?

Turn signals will definitely not work if you remove the direction warning blinker indicator relay.