Lotus Elan

Dashboard / Instrument Light Woes

PostPost by: stugilmour » Tue Feb 19, 2019 1:21 am

OK. That is weird.

For sure someone has been it there as evidenced by the non-stock plastic covered spade connectors.

Looking in the WSM on page 65 of the Electrical Section there is a drawing showing that the sidelight microswitch is the top one and the headlight microswitch is the bottom one (when placed in the normal position on the inside). Note the switches are identical and interchangeable, so this could have been changed during a previous repair.

Can you perhaps get in with an ohmmeter or test light to function test the microswitches? Just disconnect the common and one wire at a time from each microswitch to check they work as they should by pulling the light knob in and out.

Am I missing something, or are their three wires connected per switch? The top terminal on the switches is the Normally Closed (NC) terminal. It is normally not used.

Real stretch, but do you have electric pod lifts rather than vacuum? The NC terminal can be used for the pod motors to save a relay, but this is strictly a mod and non-stock.

I will look thru the wiring diagrams to see if I can see these wire colours. Red/White is listed as follows in BS-AU7 1983 Colour Code for Vehicle Wiring, from the British Standards Institution.

  • a) Sidelamp fuse to right-hand side and rear lamps
  • b) Sidelamp fuse to panel light rheostat
  • c) Fuse to panel light switch or rheostat
  • d) Fuse to fibre optic source
.

Can you see in to the sidelight momentary rocker switch to observe the wire colours on the top two terminals (2 and 3 in the diagram)? Are they with plastic covered spades indicating they have been screwed with? If you can see the wires connected to the sidelight rocker switch, those are the two to connect together to see if the sidelights come on.

Do your headlights work on low and high beam?

Can you locate the two relays for the headlights? Going purely from memory, but on the left inner fender under the hood along with the horn relay. Check the wire colours there.

HTH

Stu
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PostPost by: stugilmour » Thu Feb 21, 2019 6:45 pm

How is it going on your headlight & sidelight wiring issue?

Very snowy and cold here. Had a chance to look over the stock Federal headlight circuit.

I cannot say the attached schematic is 100% accurate, but hope it will help. I think there may be some errors/omissions/confusion in the Lotus supplied Federal diagram; the attached is my interpretation. For sure let me know if it does not match your car and I will modify it. I cannot use my car as a model because this circuit has been completely changed.

A few remarks on the interpretation

  • The referenced diagram is the one that identifies wire colours by number rather than colour codes. I have added the wire numbers to the attached schematic.
  • The headlight circuit uses the standard colour Blue/White for High (main) beam. Two gauges of wire are used, lighter gauge for the relay triggers and heavier gauge for the headlight power runs.
  • The headlight circuit uses the standard colour Blue/Red for Low (dip) beam. Two gauges of wire are used, lighter gauge for the relay triggers and heavier gauge for the headlight runs.
  • I believe the main lighting supply wire is miss-labeled on the Lotus diagram. I believe it should be Brown/Blue from terminal B of the RB 340 voltage regulator (control box). This is the standard colour reserved for headlight supply from the regulator (unfused compensated voltage control only). The number on the diagram makes no sense as I think it references 36, which is reserved for the ground loop that switches the interior lights on.
  • I cannot see what the large gauge Blue/White wire attached to the high beam relay winding terminal is used for. It may be a surplus wire in our cars. It may have been used for a flash to pass feature that we did not get?
  • Note according to the diagram the Brown/Red wire supplying the column switch changes colour at the firewall bullet connector. If this is correct, one would expect the headlights do not come on when the key is in the off position because neither the high nor the low beam relay would be triggered (with no power supplied to the column switch). I cannot recall if this is how my car originally worked. Would be great if someone can confirm that this configuration is correct and the headlights do not come on when the key is off.
  • The relay terminals are typically labeled C1 & C2 for the output Contacts (top two terminals) and W1 & W2 for the Winding or coil terminals (bottom two terminals).
  • The basic logic of the circuit is the dash mounted headlight microswitch grounds out both headlight relay windings when the vacuum headlight switch is pulled to the on position. As the headlights are Fail Safe (fail to the up position when vacuum is lost) this ensures the lights only come on when the pods are in the up position.
  • All of the Lotus diagrams show the microswitches with the top and bottom terminals used for this circuit and the sidelight circuit. The circuit should be using the Normally Open (NO) and Common (Com) terminals on the switch. The reference photo shows that this corresponds to the two terminals that are furthest apart on the switch body. However, the schematic of the switch appears to show the top terminal corresponds to Normally Closed (NC). I am not sure what is going on there, and would recommend function testing your switches to make sure you correctly identify the NC, NO, and Com terminals correctly. This may just be a running change in the utilized switch. Note Plus 2's without the Fail Safe headlight configuration utilize physically different microswitches that are located at the pods, so this difference may account for a discrepancy in the diagrams.
  • The column switch is used to select which headlight relay is activated. As only one relay winding is powered at a time the high and low filaments are never on at the same time.
  • The headlight power supply is unfused. This circuit references Federal cars that only came with two fuses, one for Green circuits and one for Purple circuits. This is one area of the stock wiring that is often upgraded if the car is rewired. I think this configuration was pretty commonly used in British cars of the period. I believe the later Plus 2's utilized a resettable overload breaker rather than a slow blow barrel fuse. Most folks just adopt the modern practice and utilize a blade fuse to protect the lighting runs.


Looking over the photograph you provided again in more detail, a few observations.

  • The headlight microswitch and sidelight microswitch may have been reversed/swapped around. This should not matter as both switches are physically identical.
  • Are the headlights presently working? The Black/Red and Black wires appear to be the correct colours. Note the headlights work completely separate from the sidelights, so it is a separate issue if the sidelights are not coming on with the headlights.
  • The sidelight switch presently appears to be using the NO and NC terminals. This is 100% incorrect if true (see terminal confusion above). The circuit should use the NO and Common terminals. The first thing may be to simply move the existing wires over to the correct terminals and see if the sidelights come on with the headlights. This assumes the previous owner has connected the non-stock wire colours back to the sidelight rocker switch, so I would personally only try this if I can see what wires are connected to the sidelight rocker.
  • The wire colours presently attached to the sidelight switch are incorrect. Note the Red/White is normally reserved for the dash light power supply loop, which runs from the dash light rocker switch to the various instrument lights. Black is normally reserved for ground. Given you were experiencing issues with the dash lights, this may have been the previous owner's mistaken attempt to get the dash lights to work with the headlights. More investigation might be needed on exactly what is going on.
  • To investigate these incorrect wires...
  • Use an ohmmeter or test light to see if the Black is ground.
  • Use a voltmeter to see if the Red/White is +12 volts when the dash lights are on.

As many of the wires in this circuit are not protected with fuses, one needs to be a bit careful while trouble shooting. One tip I found helpful is to make up a short alligator clip lead with a barrel fuse holder wired in. Place this lead from the battery positive terminal to the main battery positive supply cable. If you do accidentally create a direct short to ground this will protect the entire loom. Note this is for trouble shooting only as the starter or charging circuits could draw enough to overheat your test lead.

Hope this all helps and you get it sorted.

Ben (The Veg):

can you look over my diagram and see what you think? Particularly curious on your headlight power supply colour, what the extra heavy gauge Blue/White wire is about, which terminals are used on your microswitches for NO operation, and the wire colour used to supply the column switch at the column loom and at the firewall connector.

As a complete aside, when I did my rewire I rearranged this circuit to place the headlight microswitch ahead of the column switch +12 volt supply. The microswitch being switched to ground is probably an artifact of the original non-Fail Safe circuit, where some early cars used button switches similar to the door light switches located up with the pods.

The circuit logic is functionally the same, as the column switch is only hot when the vacuum switch is pulled out. The advantage of doing it this way is the headlight microswitch Com terminal has a Purple 12v hot at all times fused supply. This can be used to supply the NC terminal with +12v when the pull switch is in. I used this as a signal to retract the electrically driven light pods. Of course the pods rising due to loss of vacuum does not effect the electrical circuit.

HTH

Stu
Attachments
Lotus Elan Plus 2 Federal Headlight Circuit.pdf
My interpretation of the Lotus Elan Plus 2 Federal wiring diagram. The diagram is labeled RB 340 Control Box, March 1968 to March 1969 in the WSM. It is the only diagram to use numbers to identify the wire colours. A legend provides the corresponding wire colour and size.
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Stu
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PostPost by: chickenstock10k » Thu Feb 21, 2019 9:40 pm

Stu, thanks for keeping an eye on this! The weather has been been brutal and its been too cold to get into the garage after work. Thanks for all your help. I'll be back at it this weekend!
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PostPost by: stugilmour » Thu Feb 21, 2019 11:38 pm

Excellent. Wishing you luck on it. Stu
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