Pagoda SL Group
W113 Pagoda SL Group => Electrical and Instruments => Topic started by: Jordan on September 02, 2016, 21:04:39
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I absolutely hate electrical problems. Was out for a drive this past weekend and my fuel gauge suddenly went to empty. When I got home I found fuse #5 had blown. Replaced the fuse and it was good for about a minute before it blew again. Third time it blew as soon as I started the car. So I am assuming I have a short somewhere, why it developed now I don't know.
Fuse #5 operates the turn signal indicator, fuel gauge, reverse lights, brake/stop lights and low brake fluid light on the dash. If there is a short will the fuse still blow even if one is not using the function, i.e. I assume only the fuel gauge is using power when one starts the car? I would like to narrow down my options before I start taking things apart to see where I have the short, unless someone has a simpler and less invasive idea how to locate the problem. I am very receptive to all ideas.
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Best way to approach this is to start unplugging components one at a time. Ie tail lights, fuel sender etc.. You can use an ohm meter connected to the fuse terminal with the car off and see if your short "dissappears" when unpluging components. When you get to the end of the list of components on that circuit start looking for a harness issue.
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Thanks Tyler. The main reason I hate electrical issues is because I am electrically challenged. I should mention the last time I started the car and the fuse blew, I had the fuel sender unplugged. Would that eliminate the fuel sender as the culprit?
When you say hook up an ohm meter do you mean measure across the fuse gap with the fuse in/out? What reading should I not be getting or should be getting? How do I unplug the signal indicator?
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Hey Jordon,
You can also remove the fuse and with jumper wires install a low wattage bulb such as a dash bulb in place of the fuse. if there is a short the bulb will illuminate and start disconnecting one item at a time that is fed from this fuse. The bulb will go out once you disconnect the circuit with the short than you can focus on that circuit.
This also saves on fuses. ;D
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I also watched a Tech install a "short finder" (bolt)in his fuse box, started the car and watched for the smoke. Not recommended but he didn't care about the old POS.
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The entire rear wiring harness has a plug connection at the left front kick panel/firewall. Unplug it to see if the short goes away. This way you will narrow it down to the rear harness or not. Nice tip (light bulb) Jack!
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Thanks for the great ideas. Hope to get started on it this weekend and let you know how I make out.
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Finally got back to the car. Used an ohm meter as Tyler suggested and am reading about 130 ohms across the terminals (ignition off). Unplugged the fuel sender as well as rear tail lights(2 prong and 4/6 prong plugs) individually and still got the same ohm reading. Does that eliminate all but the turn signal as the source of the short?
Below is a picture of the wiring under the dash. I want to confirm this by unplugging the plug connection for the rear wiring harness as Joe suggested but not sure which it is. Is the circled connector the correct plug? Thanks.
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Marcus, use the ohm meter with one lead connected to ground and the other lead connected to the load side fuse terminal (the one that has NO power when the key is on.) You are looking for a short to ground so hook it up this way. A short will show up as a few ohms or less. The manual should state everything that is on that circuit.
The issue with using a lightbulb to chase a short is that components are grounded anyways. The lightbulb can still light up even if there is no short. The current path still has a way to ground. IE the windings in the fuel pump. Resistance measurement is crucial. However, The lightbulb trick can be useful if ALL of the components on the circuit have been disconnected and you are chasing a short within the harness.
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Thanks Tyler. Did as you suggested and I get around 1 ohm (starts at 3 and gradually drops to 1 after about 30 seconds) with everything plugged in (using negative battery terminal for ground). Get the same reading when disconnecting fuel sender, and each of the tail light plugs (2 on each side). Still would like to disconnect entire rear harness but want to make sure I am disconnecting the correct plug under the dash. Only thing north of the rear on fuse #5 would be signal indicator and low brake fluid light if I read it correctly.
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Can someone direct me as to where to find the brake light switch as well as the back-up light switch. Thanks.
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Most shorts to the rear of the car can be found under the threshold cover. It's easy to pinch the main cable while installing and sometimes it can take years before a wire goes to ground.
You can remove the driver's side inner threshold cover and have a look at the wiring. I've seen where a screw just nicked the cable and caused all sorts of trouble so I wouldn't count this out.
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Marcus, the brake lamp switch is under the dash high up. Follow the brake pedal arm up and you will find it. The reverse lamp switch is on the pass side of the transmission high up.
When chasing a circuit problem, you can usually ignore things that have some sort of switch or control positioned in the circuit. Such as brake lights. They only activate when the pedal is depressed so you know that part of the harness or lamps themselves are most likely ok. They only tie into the circuit when switched on. Find the components that are always energized by fuse #5 with the key on. The bulkhead connector that Benz Dr mentioned is the only one that its harness disappears into a large grommet on the left side kick panel under the dash. The grommet is barely visible in your pic above. Behind all the wiring you have circled.
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Thanks Dan and Tyler. Based on the wiring diagram there are 4 wires coming off Fuse 5, the brake light switch and back up light switches, which we can perhaps ignore as they are not energised all the time. Next is the fuel level indicator, which I disconnected and still had a fuse blow, so that should discount that one. Lastly is the direction signal transmitter, which I guess is also a switch?. Is the direction signal transmitter the same as the signal indicator or is it located within the signal indicator?
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Disconnecting your fuel sending unit may not do anything if you have a dead short in the wiring harness. If your signal lights work then it's probably the sending unit and more likely a shorted wire. When you do find it you will also find it's something simple and stupid - it usually is........ :)
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Thanks Dan. So if I had disconnected the sending unit and the fuse still blew immediately upon starting the car would that signify that it is the sending unit, since it is the only item hooked to Fuse #5 that doesn't pass through a switch?
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you mentioned brake fluid light. Did you check if your brake fluid is topped up? could it be that its a bit low and the short is in the brake fluid low level?
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Pinder, brake fluid is full.
Just so I am not misreading this, if the short is in the fuel sender I can still blow the fuse even if I have the sender disconnected? Is that correct? If so, how do I isolate the fuel sender, at the fuse box itself? Would I disconnect the fuel sender wire from the fuse? I've never removed the fuse box before so I assume this is doable? I told you I hated electrical issues, they give me headaches.
Thanks for the assistance.
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Yup, you have it right. You can disconnect the fuel sender inside of the trunk but I doubt it will make any difference. You can also remove the harness under the dash which should prevent any further fuses blowing.
I think your short to ground is likely under the sill trim. Disconnect both ends of the harness from the tail lights, fuel sender, and fuel pump and then test each terminal under the dash with an ohm meter. If you have anything going to ground you will get a reading.
I'm only slightly better on electrical stuff so don't feel badly. Give me a call if you need any help.
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Thanks Dan, you are far too modest. You know oceans more about electrical than I.
On that note, where is the harness connection under the dash? Can you see it in my picture above? If not I can take others.
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Marcus,
take a look at the photo here: http://www.sl113.org/wiki/Electrical/Rheostat
It shows the handshake connectors in my early 280SL. I have not seen a connector to separate the main rear and front harness parts, but perhaps I haven't looked close enough.
What happens when you disconnect the column multifunction switch?
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Marcus, the connector to disconnect the rear harness is shown in your picture, but not the one your arrow points to. It is just behind it. You can see about half of it in your picture. It is actually mounted high up on the side kick-panel, up by the firewall. It is mostly visible in your picture.
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Joe,
is this the connector circled in red on a 230SL automatic?
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Ah yes, that's it Alfred. Notice the cable goes down to the threshold cover and then back to the trunk area.
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Thanks very much. I found it on mine, mounted to the side wall, not on the firewall as it appears to be on Alfred's earlier 230SL. Tried pulling on the cover and doesn't seem to want to move. It does pull apart correct?
I also found this switch tucked under the dash. Anyone know what it is for? It pulls out and pushes in. Seems to be an integral part of the wiring. Does it get mounted somewhere? Thanks. Hope to see what I can find today.
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OK, got the cover off with some robust wiggling. It is an 11 pin connection. I used an ohm meter (one wire on ground) and took a reading from each of the 11 pins. Picture below shows what I got. Two of the pins did not give a reading and two gave higher readings (22 and 34 ohms). Don't know if there are wires connected to the two pins that didn't give a reading. Does anyone know what each pin is for?
Unfortunately I could not start the car as the fuel pump is no doubt running through this connector as I couldn't hear it whine when I turned the ignition key.
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Thanks very much. I found it on mine, mounted to the side wall, not on the firewall as it appears to be on Alfred's earlier 230SL. Tried pulling on the cover and doesn't seem to want to move. It does pull apart correct?
I also found this switch tucked under the dash. Anyone know what it is for? It pulls out and pushes in. Seems to be an integral part of the wiring. Does it get mounted somewhere? Thanks. Hope to see what I can find today.
Hi Marcus,
could that be an added switch for an emergency flasher? Nothing happens when you pull??
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Alfred, my car does not have the emergency switch as shown in your picture (there is nothing there at that location). I have everything unplugged at the moment so can't check if it is an emergency switch. It was certainly not added after the fact since the wiring ties right into the wiring harness.
Update, yes Alfred it is the 4 way emergency flasher switch. Didn't even know I had one so one good outcome so far. Does this get mounted somewhere or is it just suppose to tuck under the dash?
Would love to hear from the electrical gurus on my ohm readings and what they signify.
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..Does this get mounted somewhere or is it just suppose to tuck under the dash?
Would love to hear from the electrical gurus on my ohm readings and what they signify.
Marcus, the emergency flasher should be mounted as shown in the photo of my 1966 230SL - same year as yours!.
If you don't have a hole in the dash then you need to search for location measurements. I recall that they were posted here but forgot by whom.
It might be difficult for you to do but can you identify the wire colors for each point in your drawing?
That will help identifying the circuits.
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Thanks Alfred. Is it a definite that the flasher was mounted on the dash as in your picture? My car is a late (Oct) Euro '66. Would it have been different for the US market maybe? The knob is also different, but maybe that is an after market knob?
I'll take apart the connector to see which wires go where. Do the higher resistance or no reading pins mean anything? Those that gave a reading don't seem high so am assuming they are OK. Maybe the no reading pins, but I will see which wires go to those.
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Alfred, I just looked it up and an emergency flasher was added to US only cars on Aug 9, 1965, starting at chassis # 12497. Don't know when they were added to Euro cars or if they were ever mounted on the dash. Was yours a US car?
Labels for the emergency flasher, such as seen in your picture, didn't start until chassis 13324, 22 Sept, 1965.
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Jordan, check to see if your fuse blows with the plug disconnected.
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Joe, do you mean crank it over (pump isn't running) or just turn the ignition to just before engaging the starter? I turned the ignition to the point where I would hear the fuel pump and then turned it off. Fuse did not blow.
Below is a photo of the wire connector in the car and then which wires go to which terminal. None of them appear loose as I am able to pull each pin out and wire is well connected.
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Joe, I engaged the starter (wouldn't start obviously) and the fuse did not blow. So I assume the short is therefore somewhere in the rear wiring harness?
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Marcus,
I could identify most of the wires but not all; see attachment.
If you go to the color wiring diagram: http://www.sl113.org/wiki/Restricted/ColorWiringDiagrams
you'll see the connector #46 - use the legend for the diagram here:
http://www.sl113.org/wiki/Electrical/WiringDiagram
that should help you tracing the wires further. My hunch is that you were copying the connector side (female?) that goes to the front.
I don't understand why you have an open slot though, #46 shows 12 slots. Do you have a trunk light?
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Thanks Alfred, I missed that connector on the wiring diagram. I'll have another look at it.
I was using the mail side of the connector and do have a trunk light. I notice the trunk side has 12 wires on the wiring diagram, which is what I have, just two of the wires are sharing the same post (#1). The grey/blue wire on post 1 is the trunk light. What is a clearance light?
Do any of my resistance readings seem odd? Not sure why I am not getting a reading from 2 of them.
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Next plug the main connector back in. Now unplug every plug in the trunk, tail lights trunk light sending unit for fuel, back up lights etc. and see if the fuse blows now.
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Thanks Joe, I will try that tomorrow.
Alfred, I filled in the gaps in the sheet. I do have 12 wires, just that 2 of them are on the same post.
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Marcus,
the fact that you have 12 wires and only two doubled up is even more strange.
Take a look at the wiring diagram that Achim created - most likely for a Euro version 1966 230SL, but we need to ask him.
You should have 14 wires on the left part of the handshake connector and 12 wires on the other side. If the wiring diagram is correct then that should be the rear part of the harness but you should check that. All 12 slots (or holes) should be filled in both halves of the handshake connector according to the diagram.
To me and my very limited knowledge of electricals it makes little sense that the trunk light and the tail light (left or right?) are doubled up as you indicate!? :o
Also this wiring diagram does not tell us how the later additional emergency flasher was wired in. Lets hope someone has an answer to this.
BTW, my numbering does not coincide with your numbering of the slots/holes; I just went down the schematic.
I have an interest in this since I am also chasing a wiring problem in my 1964 230SL.
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Hi Alfred,& Jordan
Some of the cars were wired so that the trunk light only operated whenthe tail lights were on ,and the trunk open, so that would explain tthe situation here maybe.
>>To me and my very limited knowledge of electricals it makes little sense that the trunk light and the tail light (left or right?) are doubled up as you indicate!? :o <<
Have fun
Paul
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So I believe I have narrowed it down. Reconnected the rear harness, started the car and the fuse did NOT blow. Fuel gauge working, backed up the car, still working, left turn signal, still working, right turn signal I heard the snap as the fuse blew. I have lots of fuses so did it again with the rear lights and signal lights disconnected and again it blew when I used the right indicator.
So would the short be in the indicator stalk or the wiring to the rear right indicator light?
BTW, trunk light only comes on if the headlights are on.
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disconnect the steering column switch from harness and see if you can trigger right turn signal by jumping pins as described in the following link. this will narrow down issue in stalk or harness.
http://www.sl113.org/wiki/Electrical/SteeringColumnSwitch
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So I disconnected the steering column switch from the harness and my wiring looks similar to the one seen in the link. I notice that my hazard lights have also been wired in here, to pins 9 and 10. Not sure what you mean by jumping pins Pinder. Do I just attach a wire from pin 3 to 9 (right turn signal)? Then what? If I then have to test resistance do I just touch pins 3 or 9? Told you I was electrically challenged. Thanks.
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i could be wrong but jumping the pins is what the indicator switch does and in theory your turn signal light should flash just like if you used the turn signal switch. if it blows a fuse then that means its not your turn signal switch that has a problem.
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Yes jumping the mins means attaching a wire from one to the other. it completes the circuit from the power to the indicator and the indicator flasher. it should make your turn signal flash. what you are simulating is operating it via the turn signal switch. if it works and no fues blow then the problem is in the wiring from the turn signal switch connector to somrewhere up to the signal stalk or maybe inside the switch. hopefully its just in the wiring and you can fix it with no cost.
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..... left turn signal, still working, right turn signal I heard the snap as the fuse blew. I have lots of fuses so did it again with the rear lights and signal lights disconnected and again it blew when I used the right indicator. ......
Marcus,
I bet it is the column switch. You wrote that the emergency flasher is wired to pins 9 & 10 and it works without blowing a fuse. Thus I think that your forward wiring is OK, but the right turn signal switch is not. Take a look at my photo with the emergency push/pull switch; you can see the part of the switch housing. Pull yours out and inspect it (with the battery disconnected or the handshake connector separated!!) perhaps you can see the culprit, a metal chip or dislodged spring.
Test the resistance between the wire for the right turn (black/green?) and the housing. It should be very high (no short) and drop to zero when you move the lever up.
I believe a have an old 230SL column switch and if I can find it I'll shoot some photos.
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Pinder, even if I connect pins 3 and 9 how would the indicator work as it is not hooked up to the wiring harness. Or am I connecting the female ends of pins 3 and 9?
Alfred, I removed the switch housing and I am not seeing anything loose or anything that might be out of place. Springs are all good, although my right indicator often does not stay in place. It will often automatically jump back. Everything is so well packed into the switch I could not identify which was the black/green wire. I did recheck the emergency lights and all four corners flash when I engage the emergency switch without blowing the fuse. Picture quality isn't the best but hopefully you can see the various sides of the switch housing.
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Marcus,
here are photos of my defunct 230SL column switch. The normal wiring comes in from the back where I have attached the alligator clips for testing. There are three soldering posts for the turn signal wires. The top row shows the switch in the normal position (stalk is straight) on the left and the Ohm meter shows a "1" meaning more than 200 Ohms (note setting). Pushing the switch to the side (which I believe should be the up or right turn position) opens the connection and the resistance goes to 4 Ohm.
The lower row is the opposite.
The actual switch is under these three soldering posts; also see your photo that I modified.
If you follow those wires to the end connector you should be able to test the switch as I did.
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Alfred, thanks, I was able to identify the correct wires (I marked them below). Unfortunately or maybe fortunately I got 200+ ohms with the stock straight and just over 1 ohm when I flipped the switch, both left and right. The reading would start at around 3 and drop down to just greater than 1 over about 10 seconds. So that would signify the column switch is OK and the short is elsewhere?
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Try disconnecting the main rear harness again and activate the turn signal combination switch. If the fuse does not blow, then it must be in the rear harness or rear devices.
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The pins to jump / connect are on the socket where the switch plugs into. not the switch itself. once you disconnect the switch from the plug the switch is no longer part of the circuit. all the switch does is jump wires. when you use the right turn signal it makes the connection from the two pins mentioned earlier.
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Thanks to everyone for their assistance but the short seems to have disappeared. When I pulled apart the column switch connector I found corrosion around some of the pins which was cleaned up with a fine wire brush and some electrical cleaner. This didn't fix it since the fuse continued to blow but it was good to get this taken care of before it became a bigger issue. However, since taking apart the actual indicator switch, moving various wires to see what I had, cleaning everything (including the female connector), putting it back together I no longer have a short. Not sure what I did and maybe it will come back but for now it seems to be sorted out. Could have been something as simple as two wires touching which was fixed by taking things apart. Kind of anticlimactic. No eureka moment.
With the assistance of this group I did learn a lot more about the wiring in these cars, found my hazard switch I didn't know I had and finally put a bulb in for the trunk light. Many thanks for every ones help.