Light Problems - Interior and Exterior

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Light Problems - Interior and Exterior

Postby LotusEnthusiast » Tue 27.06.2017, 18:36

Hey guys. Got my Elan back to road worthy, its driving great and looks even better. However I have some problems with my lights now...

My interior lights do not work. The cluster lights and the gauge lights (boost, oil pressure and volts). However the warning lights below the speedo/tach work. And so does my fuel light work.
My right rear brake light doesn't work when I turn my lights on but it works when I brake. My right front indicator lights don't come on either unless I turn the blinker on. Strange stuff especially since it is only on the right side.

Could someone please point me in the right direction to be able to fix this? The bulbs work so it must be a wire, ground or fuse I'm guessing.
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Re: Light Problems - Interior and Exterior

Postby lotustonybassplayer » Tue 27.06.2017, 22:36

has the rheostat for the dash instrument lighting been turned down ?
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Tue 27.06.2017, 23:05

Basically, the brake light has a duel filament bulb and it is probable that the tail light element is burned out/broken. It takes a standard 1157 bulb.

Was there any work done behind the dash or in that area? Could a ground have been left off? I am assuming by interior lights you mean the dash lights or are the actual interior lights (in the rear view mirror) not working too?

The tell tale lights and indicators like low oil pressure and charging light are independent from the dash/instrument lights so you should see other lights even when the dash lights are being ornery.

There is a dash illumination rheostat and control module in place to adjust the gauge lights to your preferred setting. As Tony asked, is it turned down?

A little more history as to what was done to get the car road worthy might be helpful to point you in a general direction. Also calling the different systems by their proper names will also keep us from going off target with our suggestions.

You can email or call me (North Carolina) if you want some help with the electrical part of the dash lights. It isn't a standard variable resistor like the old British cars ie TR/MG/Jag, etc, it is actually a PWM regulated system.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Tue 27.06.2017, 23:55

Brit-Car-Nut wrote:Basically, the brake light has a duel filament bulb and it is probable that the tail light element is burned out/broken. It takes a standard 1157 bulb.

Was there any work done behind the dash or in that area? Could a ground have been left off? I am assuming by interior lights you mean the dash lights or are the actual interior lights (in the rear view mirror) not working too?

The tell tale lights and indicators like low oil pressure and charging light are independent from the dash/instrument lights so you should see other lights even when the dash lights are being ornery.

There is a dash illumination rheostat and control module in place to adjust the gauge lights to your preferred setting. As Tony asked, is it turned down?

A little more history as to what was done to get the car road worthy might be helpful to point you in a general direction. Also calling the different systems by their proper names will also keep us from going off target with our suggestions.

You can email or call me (North Carolina) if you want some help with the electrical part of the dash lights. It isn't a standard variable resistor like the old British cars ie TR/MG/Jag, etc, it is actually a PWM regulated system.


The rheostat has never worked, so I ordered a new one plus the module from SJsportscars. I did a little work behind the dash but I don't think I left a ground off or anything but I'll check again. Only the dash lights don't work plus the gauge lights. The light in the rear view mirror turns on and all the warning lights work too. As for the exterior lights, my left side lights work but my right side doesn't. My headlights work btw. Its very strange.
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Wed 28.06.2017, 00:20

The dash lights and the gauge lights are the same circuit. Hopefully the rheostat and module will cure that.

Exterior Lights: Each side is independently fused, so maybe you have a fuse issue? Do both of the front parking lamps come on?

You will notice the rheostat circuit gets its power from the RH circuit (as does the digital clock), so a bad fuse A7 could be the culprit.

Here is the circuit:

Side-Tail Lamps.jpg
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Wed 28.06.2017, 21:48

Changed the fuse, nothing changed. Also changed the bulbs. Nothing. Only the left side parking lamp comes on. All my exterior lights on the left side work. None of my exterior lights on the right side work except the headlights.
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Re: Light Problems - Interior and Exterior

Postby lotustonybassplayer » Wed 28.06.2017, 21:57

Is the digital clock working ? as that takes a feed from the right side according to the wiring diagram, just seen John has already mentioned the clock :bonk:
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Wed 28.06.2017, 22:19

Yes the clock works.
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Wed 28.06.2017, 23:19

To decide if it is a power source issue, get an in-line test light (Harbor Freight has cheap ones), get it connected to a GOOD ground and with fuse A7 removed, test each side of the fuse socket (with the headlamp switch turned on). If you don't get power anywhere, you have a bad fuse box since IPHC also feeds the circuit for the LH side lights too. If you get power at one side of the connector, put the fuse back in and test again (both ends. If you still get power at one end but not the other, the fuse is bad or the socket is dirty. If you get power at both ends, then get access to the RH rear tail light assembly and disconnect one of the red/white wires at the tail lamp and test for power there - remember to find a GOOD ground for the test light. If yes then there is an GROUND issue or a bunch of bad bulbs. If no, then make a fused test wire that will take power from the battery + and touch it to the brass connector in the wire you disconnected. I will assume the fuse didn't blow. Did the other RIGHT Side lights come on? Looking more carefully at the diagram, they show the clock light gets a connection at the IPHC too.

There are several tail light bulbs in the tail light that also get fed by the red/white, so they should have come on. If they didn't then you have a ground/earth issue or a lot of dirty sockets. If they did, then the circuit is broken between the fuse and the light bulb connector. All you can do is start at the beginning and test EVERY connection point labeled in the circuit diagram until you find one that doesn't have power. Go back 1 connection and that is the one that is bad.

To make a fused test wire, get a length of primary wire either 14GA or 12GA, a LARGE alligator clip (for the battery end) and a smaller clip for the test end (Radio Shack, Auto-Zone or NAPA) and also get an in-line fuse from the automotive department. Combine all of the pieces and take the connections so they can't short out.

If you look at the wiring diagram, there is only one source of power for that entire circuit. By creating another source of power to the circuit, you will eliminate the 5A fuse at A7 and everything should work.

It is hard to write a test process that takes everything into account, so if anyone sees a section of circuit I didn't show a test for, jump in...
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Re: Light Problems - Interior and Exterior

Postby lotusflasherman » Thu 29.06.2017, 00:20

Don't know how this affects US models, I'll leave John to advise on that, but certainly is an issue with UK cars...

Service Bulletin 1991/25 dated 09/12/91 changed the logic for the instrument lights to move them from the lighting circuit onto the ignition. The theory was that it would stop condensation forming behind the glass on the small gauges and allow you to park with side lights on and no battery drain from unnecessary instrument lighting. It was implemented in the factory in October '91 from VIN 6251 and dealers may have updated earlier models with a supplied kit, or they may not have !

So what the car actually has may take a bit of research. I have a Jan '91 registered SE with them still on the lighting circuit, so never changed, and a Dec '93 registered, built in last week of production, with them on ignition circuit from the factory. The later car isn't troubled with condensation but having the lights on all the time has caused the black paint in the small gauges to deteriorate and let the light shine through, so I wouldn't recommend rushing to implement that change.

Also, I have never seen an updated wiring diagram for the SE, my copies are Nov 1990 prior to the bulletin, but the S2 diagrams (1995/01) do show the instrument lights on the ignition circuit.

Details of Bulletin 1995/25 are shown below for convenience .. (pages are sideways to allow me to post a better quality file for you to print.)
1991 25 a.JPG

1991 25 b.JPG


Might be worth checking if you can see any of the wires shown in the bulletin and if so, have they dislodged or dropped out ??

Good luck...
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Thu 29.06.2017, 02:07

Phil: The FED cars are all before the change point for this mod. He is saying that NONE of his right side lamps are coming on: Front, Park, Tail and our "side" lights (in the bumpers).

Since these get their grounds/earths from multiple locations, it is unlikely that they are all suffering from a lack of grounding.

I am still voting on a fuse/fuse socket issue, but looking forward to the results of a front to back test.

Here is the fuse box layout and location:

Fuses.jpg
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Thu 06.07.2017, 02:23

I've been busy and haven't been able to work on the M100. However my parts from SJsports cars came in! I'll get to work tomorrow to try and figure out this problem.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Thu 06.07.2017, 19:58

Changed the rheostat and rheostat module and nothing changed.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Sat 05.08.2017, 21:56

Got all my exterior lights working. However still no interior lights.
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Sun 06.08.2017, 13:09

It would be nice if you described what you found and had to do to get the exterior lighting to work. Others may run into the same issue and it would be nice to provide a possible solution.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Mon 07.08.2017, 17:54

I read the fuse box wrong and had my fuses mixed up. :bonk: Putting on a new convertible top this week with all new seals. Hopefully I can figure out my interior lights, it must be the ground wire, but idk where the ground wire is looking at the wiring diagram that must be it.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Thu 05.10.2017, 02:08

Alright guys. The convertible top and seals are on the car and look very good. Interior is coming together nicely too. However; I still have no interior lights. I have no clue what to do unless I hot wire the lights to work. I've changed everything I needed and nothing. It must be a ground wire but I can't find it... Any suggestions or a picture of where the grounds are?
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Thu 05.10.2017, 03:51

I believe most everyone has been assuming you meant the dash / instrument lights were out, not the 2 interior lights at the rear view mirror.

Please clarify which is causing your problems.

Grounding locations are found in the Electrical Manual section MJ.6

According to the circuit diagram, the interior lights all get their ground from ground #2 which is at the pedal box and also connects to the firewall and then by a braid to the longeron.

It should be easy enough to test by removing one of the bulbs and using a jumper wire to clip to the ground end of the bulb socket and ground that wire to a good ground. If the other light now works, then you are correct and you should trace the ground circuit to the chassis braid at the longeron.

Of course, that is assuming the wiring diagram available is correct for the FED car as well as the UK SE.
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Re: Light Problems - Interior and Exterior

Postby LotusEnthusiast » Thu 05.10.2017, 04:03

Yes it is the dash/instrument lights. My lights on my review mirror work. I'll take a look at the manual and try and figure it out tomorrow. It has to be a ground...

Thanks
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Re: Light Problems - Interior and Exterior

Postby Brit-Car-Nut » Thu 05.10.2017, 04:48

Then please call them panel lights or dash/instrument lights.

DO NOT bypass the dimmer circuit as it is a PWM device and at "full" brightness, there is only around 60% going to the bulbs. Bypassing the circuit will cause the lights to get full power and they will damage the gauge faces.

Here is the circuit:

Panel.jpg


Here are the connections:

Connect.jpg


You will see that ground circuit #2 is also the one for this circuit, so it isn't a main ground issue.

There is a connection in-line: IPCHC Plug C which is using pin #4. You need to find this connection in the harness plug and test it.

You can also test by getting to a bulb that isn't glowing and add a temporary ground to the ground side. I think that all of the dash lights are twist in bulb sockets that go into the flexible circuit board so that might be difficult.
I haven't looked at an instrument cluster in a long while, so this might be a regular in-line plug. Look for it.

The flexible circuit board connection might also be dirty or damaged. Remove the plug and look at the connections. They are fairly primitive. Clean/fix what you find. I believe new flexible circuit boards are still available if yours is damaged.
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