Turn Signal indicators, 2 instead of 1 |
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Turn Signal indicators, 2 instead of 1 |
jk76.914 |
Jul 6 2006, 11:35 PM
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#11
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Senior Member Group: Members Posts: 809 Joined: 12-April 05 From: Massachusetts Member No.: 3,925 Region Association: North East States |
All right. Back again. Here's the schematic for the '70 - '73.5. These are the cars with separate left and right indicators at the top of the tach, and the high beam indicator along on the bottom...
Thankfully, the flasher works the same as in the later models that only have one indicator, which was covered in my earlier post. When you look the indicators, it gets weird- The same blue/white wire goes to the tach, and it hooks to BOTH bulbs. The other lead of each bulb, instead of going to ground, actually goes to the turn signal circult that goes off to the bulbs themselves. BUT WAIT!!! The LEFT indicator is connected to the RIGHT circuit, and the RIGHT indicator is connected to the LEFT circuit. (IMG:style_emoticons/default/WTF.gif) If you study what's going on, you see it. When the left turn signal is on, the flashing signal trailing out to the bulbs is +12v/0/+12v/0/+12v/0 and on and on. The same signal is coming out from the secondary relay to both indicator lights. This signal is in phase with the primary flashing signal, so the indicator that is connected to the left turn signal WILL NOT FLASH because it will see +12v on both leads at the same time, or 0 on both leads at the same time. There will never be a voltage differential that will cause it to light up. And which indicator do you NOT want to see flash when the left signal is on? That's right- the RIGHT one. So what happens with the left indicator? It flashes! Because one lead is connected to the same secondary flashing output that the other indicator is connected to, but its second lead, which is connected to the RIGHT signal circuit IS GROUNDED THROUGH THE TURN SIGNAL BULB FILAMENTS THEMSELVES! (let sink in) This grounding scheme works because the indicator bulb is much lower wattage (meaning much higher resistance) than the main signal bulbs, so it lights up and limits the current in the circuit to a level below which the main bulbs turn on. So that's pretty tricky, but it's not over yet! What happens when a bulb is out? Well, the secondary relay in the flasher stays open, as before. But what a weird-ass result that has- BOTH INDICATORS FLASH TOGETHER when the side with the missing/wrong/corroded/LED/whatever problem is turned on. (IMG:style_emoticons/default/WTF.gif) If you look at the circuit, you can see what's going on- with the output from the secondary relay floating, you have both indicator bulbs, in series, completing the circuit from the side that's on (+12v or thereabouts) to the side that's off, and grounding through the filaments of the big signal bulbs again! The indicators are a bit dimmer, because they're wired in series, but they flash together. If you replaced your indicators with LEDs, this cannot happen. The back-to-back series LEDs will block current flow. In this case the indicator that a bulb is out is that the indicator LED on the side with the bad bulb will remain off when that side's turn signal is turned on. So that's about it. These two installments show the before and after circuits for incorporating early dual indicators into late tachs... Plus enough info to dispel myths that are drifting around about grounding problems, diodes in the harness, etc, etc, etc..... You can now also figure out how to diagnose problems better. For example, if the dash indicator light is on, but doesn't flash, it has to be a bad flasher. If the signals flash, but the indicator is steady, it's the secondary relay in the flasher. If both stay on, it's the primary relay in the flasher (probably) or the solid state timing circuit in the flasher (unlikely). etc, etc, etc.... |
bd1308 |
Jul 6 2006, 11:51 PM
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#12
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
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John |
Jul 7 2006, 12:30 AM
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#13
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member? what's a member? Group: Members Posts: 3,393 Joined: 30-January 04 From: Evansville, IN (SIRPCA) Member No.: 1,615 Region Association: None |
I found the answer several months ago in UpFixin vol IX on Pages 171 and 172.
They show the additional wire required (as was installed in 1970-1973 cars) for the individual indicators to work. jk76.914 has it right. Two wires are added: green/black and white/black are added between the flasher relay and the indicator bulbs. The blue/white wire is terminated to the other side of both bulbs. BTW, did you know that PCA is giving away sets of the UpFixin der Porsche? I saw an add in last month's Panorama and got my set today in the mail. It is missing Vol 7, but otherwise it is complete and only cost me shipping. |
BigDBass |
Jul 7 2006, 06:53 AM
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#14
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Dumb Question Champion Group: Members Posts: 1,438 Joined: 11-January 06 From: Chicago (south 'burbs) Member No.: 5,405 Region Association: Upper MidWest |
Thanks for the excellent description.
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Rusty |
Jul 7 2006, 08:51 AM
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#15
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Wanted: Engine case GA003709 Group: Admin Posts: 7,941 Joined: 24-December 02 From: North Alabama Member No.: 6 Region Association: Galt's Gulch |
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tdgray |
Jul 7 2006, 11:41 AM
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#16
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Thank God Nemo is not here to see this Group: Members Posts: 9,705 Joined: 5-August 03 From: Akron, OH Member No.: 984 Region Association: None |
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jim_hoyland |
Jul 10 2006, 09:07 PM
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#17
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Get that VIN ? Group: Members Posts: 9,303 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
Good description; would you mind adding a few words to guide me through the rewiring..say I under the dash and have the fuse panel out and I have the speedo loose with the back visable. Which wires am I going to modify...it would be helpful.
I.m going to re route the the signal to the ERG and CAT bulbs Thanks, Jim |
John |
Jul 11 2006, 01:13 AM
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#18
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member? what's a member? Group: Members Posts: 3,393 Joined: 30-January 04 From: Evansville, IN (SIRPCA) Member No.: 1,615 Region Association: None |
Jim,
You would add two wires from the emergency flasher switch to the bulbs you will use (green/black and white/ black). These are the same wires and colors leading out to the turn signal bulbs at the four corners of the car. You will modify the existing blue/white wire to extend to the other side of BOTH bulbs. The blue/white wire terminates at the flasher relay itself. Attached thumbnail(s) |
jk76.914 |
Jul 11 2006, 08:28 AM
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#19
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Senior Member Group: Members Posts: 809 Joined: 12-April 05 From: Massachusetts Member No.: 3,925 Region Association: North East States |
That's right. I didn't want to pull out the emergency flasher switch though. It looked like too much disassembly, and right now, I'm trying to focus on assembly! So once I dropped the fuse panel, I found the correct wires running overhead of it and cut them and spliced them right there on the spot. In the photo, the spot I found is above the rear edge (rear being toward the rear of the car) of the fuse panel, about just below the hazzard flasher switch. Wire gauge to the indicator lights doesn't matter really. The other place I considered tapping into is under the center console/cushion. This same circuit runs to the rear taillights. Finding the wires above the fuse panel was much easier and more straightforward, but that shows how much I didn't want to remove the hazzard switch.... It's easy to cut and splice a very reliable connection. I always solder and then use shrink wrap. Just be sure to slide the shrink over the cut end before you solder. Guess how many times I've learned that? duh. While I was changing gauges (this is a '76), I rebuilt mine. You may notice the early style gauge faces and pointers, but the later style shallow trim rings... That's because my '76 rings were perfect, but the deep-dish rings on the donar gauges had been repainted with a brush and looked pretty bad. I also kept the early glass lens vs. the later plastic one.... Gave me a chance to fix that blackened high beam indicator lens at the same time. ...I still have to get to the combo gauge.... Looking ahead for once, I also spliced on a second, longer wire lead to each turn signal circuit that I coiled up and stuffed in the console. These will later go to the repeater lights that I am adding later on the sides of the car..... The green wire in the photo is one of these- I've got to dress it better than that! Good Luck! Jim |
jim_hoyland |
Jul 11 2006, 08:47 AM
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#20
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Get that VIN ? Group: Members Posts: 9,303 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
Thanks for the installation detail--makes sense to me. I'll give it a try this weekend, let you know how it works.
Jim Hoyland |
jim_hoyland |
Jul 11 2006, 09:39 PM
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#21
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Get that VIN ? Group: Members Posts: 9,303 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
One last question; do the repeater lights ground to the body...I would think so, but want to make sure.
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jk76.914 |
Jul 12 2006, 07:18 AM
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#22
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Senior Member Group: Members Posts: 809 Joined: 12-April 05 From: Massachusetts Member No.: 3,925 Region Association: North East States |
That's right. Just like the front and rear signals. Are you adding them as well? Have you picked one? I'm using '90s vintage Saab repeaters. They look right, and they don't need a recess in the fender, just a hole.
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jim_hoyland |
Jul 12 2006, 11:18 AM
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#23
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Get that VIN ? Group: Members Posts: 9,303 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
The Saabs sound good; would you have the part number(s). I'll prolly order them now and do the install much later. Can they be ordered on-line ?
Thanks again, Jim |
nivekdodge |
Aug 6 2022, 10:06 AM
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#24
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Member Group: Members Posts: 250 Joined: 28-August 21 From: Pittsburgh Pa Member No.: 25,860 Region Association: MidAtlantic Region |
Wow someone else had to do this
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