Topic: Found Flashers, But Not the Fix

[kkupec02]

I found the flashers on top of steering column brace. Couldn't be seen from under dash at all. Couldn't see them until defroster plate off, speedo disconnected, instrument panel dropped and plate above radio off for the angle view. Replaced the flashers to no avail. Right front signal light housing off and disconnected. Brake switch off and disconnected while booster and MC being rebuilt. Problem persists. Running lights both sides good front and back. Left signal good. Right signal rear bleeds to left signal rear, both weak. Front left signal stays off. Emergency flashers activate light left side only. Right rear doesn't light. I replaced voltage regulator and 2 flasher housings so far. Once I get new front signal lamp housings from Branda and  installed, I'll have to see what happens next. While the dash is apart, I may have to start tracing wires, an impossible task with wiring looms. Probably should get signal housings installed and brake switch active to make sure that they are not affecting system while being off line. Can't wait.   

[jwc66k]

Shown on pages 18 and 21 of the 67 Mustang Electrical Manual.
Jim

[kkupec02]

Actually, I did make some headway. Right hand side running lights were weak before I took the right front turn signal offline and found that it didn't test well.

[Coralsnake]

Make sure you have the correct type bulbs in each socket. Some sockets are single filiment while others are double

Usually everything has to be connected to work properly

Also take a look a steering column switch if you continue to have issues

[67gtasanjose]

Ok...a simple step-by-step for 67- newer turn signal circuits:

Each turn lamp circuit has a wire (or two for front lamps) which supplies 12 V power to each of the turn signal or turn/stop lamp bulbs. Testing begins at the under dash steering column connector (at the steering column plug). You will need to identify each one of these 4 circuits.

1.) Look at the schematic to identify the color code for the wiring used in each of these 4 circuits.

2.) Plug in all "known as good" lamps with bench-tested bulbs in them.

3.) At the main underdash harness connector (with the column switch unplugged)," using a jumper wire attached to a fused 12v source, power up each one of these 4 circuits, one-by-one and go look at the lights and indicator lights in the cluster.

4.) Identify any abnormalities of these lights such as:
 a.) Does each lamp light brightly (including front indicator lamps in cluster)?
 b.) Is there any feedback into the park lamp or tailight circuits? (Usually feedback is caused by bad grounds).
 c.) If all lights work correctly one by one, the problem is not in the lamp portion of the circuits, the problem would then be in either in the turn signal switch or flasher can circuits.

5.) Flasher Can Circuit Test:
 a.) Using a test light (clamped to good ground), probe the plug the flasher can plugs into, 12V should be present with Key On for turn signal flasher can and ALWAYS for hazzard flasher can.
 b.) Check continuity between the other wire (without the 12V source), to the column connector. (The color of this wire WILL BE THE SAME COLOR WIRE at the flasher can and the column connector).
 c.) A load test of each 12V supply for the flasher cans can be done by using a homemade jumper wire with two spade terminals and a few inches or wire, (plugged in, in place of the flasher cans), this would provide an uninterrupted 12V supply to the turn signal/hazard switch so if all the lamps have passed their tests, theoretically, now if the signal switch itself is good, your lights would work without flashing.

6.) Brake lamp circuit needs tested. (research needed here, above knowledge was by memory only).

[kkupec02]

Thanks. I'll print out your piece and take it out to the garage this weekend.

[kkupec02]

I still have to do the tests recommended by 1967gtasanjose. I did some tests on the horn system thinking that would be the easier place to start. I did some horn tests recommended by a member of the vintage mustang forum. Bottom line, I have low power everywhere with a new voltage regulator, what seems to be a new battery(just bought car) but I am missing main ground from engine to fire wall while engine starts great. I got the following results:

With battery disconnected, disconnect both horns, then temporarily install a jumper wire from one horn connector to ground. In the car, measure resistance of the horn contact to ground. Then move the jumper wire to the other horn connector and repeat the resistance measurement. Lastly connect the meter leads together and provide that measurement. Report back with all three values. I would expect all three to be near zero. FEMALE HORN CONTACT WAS GROUNDED THEN RESISTANCE CHECKED BETWEEN HORN CONTACTS IN CAR. DRIVER SIDE 28 OHM, PASS SIDE 36 OHM. NOT GOOD. METER WAS 0.

Next I would move to a functional test. Battery installed, one horn installed (including being bolted in place which provides the necessary ground path), and use the device of your choice to safely make the horn contact make. While the horn is blowing, have a second person measure the voltage at the other (disconnected) horn terminal. This will tell us the voltage drop up to the horn. Repeat for the other horn. Report back with both voltages. WHEN PASS BLOWS, DRIVER 9.7 VOLT. WHEN DRIVER BLOWS, PASS 9.6 VOLT. NOT GOOD.

Lastly install both horns and engage the horn contact, making sure that both horns blow. If you can get a probe in an exposed part of the terminal at one horn, while it is connected, it would be nice to know what the voltage is when both horns are energized. This would be the final test, and give you assurance that you can put it back together. 8.3 VOLT AT PASS, 8.4 VOLT AT DRIVER. NOT GOOD.

Given the other issues you have had, I would also test headlights, driving lights, turn signals, emergency flashers before installing the steering wheel. These would all be functional tests, and would validate the steering column switch, wiring, flashers, etc. NEW STEERING HARNESS 11.6 VOLT AT HORN CONTACTS. BATTERY 12.24 VOLT AT REST. WHEN HORNS BLOW, 8.9 VOLTS AT PIN IN CONNECTOR PLUG CHASSIS SIDE BLU/YEL, BUT ONLY WITH A SHARP PROBE SO QUESTIONABLE CONTACT. CHECKED VOLTS WHILE RUNNING LIGHTS ON AT TAIL LIGHTS. 8.6 VOLTS ON RIGHT, 6.2 VOLTS ON LEFT.

Problem seems to be low voltage everywhere. Battery seems new but maybe should replace? Just replaced voltage regulator with no change. I see no ground strap between engine dip stick and firewall, but engine starts right up. While I was doing these tests, got a new problem. Connected the battery and suddenly had no turn signals or emergency flasher, but had headlights. Disconnected it, reconnected it and flasher/turn signals worked again.   

[Bob Gaines]

It still sounds like a ground problem to me. The starter works good because the battery negative cable ground goes directly to the engine block. The starter is bolted to the engine block =ground path.The small ground cable on the head to the firewall has basically nothing to do with the starter.Obviously the engine block has ground contact to the chassis in small ways which are typically weak which is why systems can work even when the small ground wire from the head/firewall is not attached. The ground from the block to the firewall assures a good ground to all things grounded to the chassis .The small ground from the head to the firewall insures a good ground from the engine block to the sheet metal chassis of the car. At least if those individual systems have a strong ground between them and the chassis.  All of the points that you have ground wire to the chassis or are bolted to the chassis for ground and are systems that you are having a problem with you should go back and make sure they have a good strong ground .  Like the horns that I said to remove the paint for metal to metal contact and use dielectric grease to prevent corrosion . The firewall ground should have a gold star washer to dig into the metal to create a good ground same on the head .  Same with the regulator.Same with the large bolt where the battery ground and the alt ground bolt to the block. This can be done without compromising the correct look.You may have multiple ground issues so maybe not one thing will solve them all. At the very least AFTER confirming ALL grounds in the problem areas are good and strong ,attach a temporary ground between the head and firewall until you get a permanent one . After you have confirmed you have good grounds all over you can move on to the next thing on your list.  No use wasting more time until you get that done IMHO.

[kkupec02]

Thanks. I am thinking some major ground as well as other issues like the horn wire itself with the bad resistance. By the way, I did mount the horns as you suggested. I took the paint off of the horn bracket and the radiator support. I then used dielectric grease and aluminum foil. So I am good with that ground. I'll have to recheck all grounds which come to mind such as battery, voltage regulator, engine to firewall, solenoid and any others that I can find on electrical shop manual pages.

[Bob Gaines]

Thanks. I am thinking some major ground as well as other issues like the horn wire itself with the bad resistance. By the way, I did mount the horns as you suggested. I took the paint off of the horn bracket and the radiator support. I then used dielectric grease and aluminum foil. So I am good with that ground. I'll have to recheck all grounds which come to mind such as battery, voltage regulator, engine to firewall, solenoid and any others that I can find on electrical shop manual pages.

Besides the "shop" manual you would be well advised to get the assemblyline "electrical" manual as well . For that matter you should get the entire set . The illustrations will save you hours of time and answers untold questions. They also tell you the correct fasteners that were used and the finish . You will need to get the AMK guide to fasteners companion book to decipher the fasteners codes. Thes are available from larger vendors

[67gta289]

Due to the low voltage I'm thinking the problem is on the high side, not the ground.

With battery in, but no load (with door shut so no interior lights), measure the voltage at the fuse panel.  Should be near 12V, assuming your battery is near 12V.

Then open the door and measure that same voltage.

Then turn on your blower motor, or blow the horn; both are significant loads.  What is the voltage now?

We are looking for the voltage drop.  Dirty contacts/surfaces and/or partially broken feeder wire.

[midlife]

OK, time for me to chime in.  I have been refurbishing headlight harnesses for 12 years, and horn lines are often a problem.  I measure continuity from the input side of the headlight harness (black square 4 pin plug) and measure continuity to the closest horn female spade, then the farthest female spade (the two horns).  More than 50% of the time I get crappy readings.  I then use a small jeweler's screwdriver to push the locking tab back on the black plastic cover at the horn contact and remove the cover.  Inspect the female spade: they are often rusty.  Clean as best as you can, and re-test.  If still high resistance (my personal metric is 0.9 ohms or less), then re-crimp the pin.  95% of the time, the re-crimp does the trick.
The high resistance at the pin, along with corrosion on the pin itself, accounts for the high resistance and voltage loss you describe.
Of all the test procedures for measuring voltage, current, resistance, etc., I have found that continuity with everything unplugged gives the most reliable look at what the problem is.