Lotus Elan

S4 Federal Blinker Trouble

PostPost by: Temmck » Tue Jun 14, 2022 2:29 am

I have most of the electrical issues worked out but I have one trouble spot with the right side blinkers.

The left side works fine and the hazards work on all four corners but the right side blinkers are challenged. If I just turn them on I can hear the DB10 relay pickup but it makes a whining noise and none of the lamps light. However, if I run the flashers for a few seconds, turn them off, then turn on the right side indicators, the right side front and rear lamps blink as normal for about 3 or 4 blinks then the blinks start to slow down and then stop with the lamps lit and the whining from the DB10 starts again. The whine gets louder and the indicator bulbs get dimmer and then finally go off but the whine continues.

The flashers and left side indicators work correctly every time.

The only thing I can think of is a poor connection from the turn stalk to the hazard switch. That seems to be the only wire that is unique to the turn indicator circuit.

Does this sound familiar to anyone?
Temmck
First Gear
First Gear
 
Posts: 45
Joined: 23 Aug 2012

PostPost by: Andy8421 » Tue Jun 14, 2022 6:00 am

This is a tricky one.

If the wiring diagrams are to be believed, the indicator stalk is not in circuit with the flasher unit / bulbs, it just energises a relay in the DB10 to switch the indicator circuit on. This is the same relay that the hazard circuit uses, so if the hazards work the indicators should as well. A fault in the stalk / hazard switch wouldn't explain the flashing slowing down and stopping.

Some suggestions:

You mention that the stalk / connection is the only part of the circuit specific to the right side - not quite true, the right side blinkers are of course also specific. If (say) the wrong wattage bulbs were in the right hand side (or a poor earth to one of the light fittings) this would explain the behaviour of the flasher - which is current sensitive. A wrong bulb / poor earth in one corner wouldn't have the same effect on the hazard flasher as it would be 'diluted' by the other bulbs. So step one, check the bulbs and earths on the right side indicators.

The DB10 is two relays in one, and I can't fathom how it would whine. I could imagine a buzz if there was a weird earthing problem, but a whine is difficult. Is there anything electronic in the car nearby that could be making the sound? Or have you replaced the standard bimetallic flasher units with modern electronic equivalents?

Let me know how you get on.

Edit:

This link explains how the DB10 and hazard switch are supposed to work. It is a surprisingly subtle design given the generally poor wiring design on the Elan.

https://www.gglotus.org/ggtech/relaybox/body-relay.htm

Andy.
68 Elan S3 HSCC Roadsports spec
71 Elan Sprint (to be restored)
32 Standard 12
Various modern stuff
Andy8421
Fourth Gear
Fourth Gear
 
Posts: 785
Joined: 27 Mar 2011
Location: Surrey, UK

PostPost by: Temmck » Wed Jun 15, 2022 2:08 am

Spot on Andy!

I tried to recreate the problem I encountered yesterday but the right side is now blinking but at half the rate of the left - 1 blink per second VS 2 blinks per second. I could not replicate the no blink scenario but I did swap the right side and left side bulbs and the slow blinking moved with the bulbs. I then moved just the front bulbs back to the original side and the slow blink stayed on the left. So, rear left bulb is suspect. Its resistance is not much different from the others but, I will replace all with the same type bulb.

Thanks again.
Temmck
First Gear
First Gear
 
Posts: 45
Joined: 23 Aug 2012

PostPost by: Andy8421 » Wed Jun 15, 2022 5:48 am

Glad to be of help.

Bulbs are 'non ohmic', the resistance of the bulb changes significantly when it switches on and gets hot.

Comparing the resistance cold is only half the story, depending on filament material, thickness, operating temperature, it could be that one of your bulbs behaves differently to the others when hot and is 'the odd man out' causing the problem.

These problems can be difficult to find, and do give some insight into the challenges faced by the designers of the day who had to make all this stuff work reasonably reliably at a specific price point with little more than a few bent bits of metal and a couple of poor quality relays.
68 Elan S3 HSCC Roadsports spec
71 Elan Sprint (to be restored)
32 Standard 12
Various modern stuff
Andy8421
Fourth Gear
Fourth Gear
 
Posts: 785
Joined: 27 Mar 2011
Location: Surrey, UK

Total Online:

Users browsing this forum: StephenT and 13 guests