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MOT failure

johnjolly

Enthusiast
Messages
144
#1
Overzealous MOT tester today failed my R4 Savanne 1991, because hazard warning lights only work with ignition switched on. Is he right?
I have live, to unswitched feed into hazard switch, but without the ignition on, indicators won’t work. The ignition has to be on.
My best guess is that perhaps a relay has failed but where do I locate it, and how can I test it?
There was also some interference connected to headlights being on when he demonstrated the fault but this had cleared by time I was home and investigating the problem.
 
Messages
330
#2
Your hazard switch has not been wired correctly and it's easy to fix. The hazard switch performs TWO functions when it's switched on.
1/ When the hazard switch is OFF the hazard switch is bypassed and power to the flasher unit passes from the power supply (an "ignition live" feed) through the hazard switch, to the flasher unit, the indicator switch and finally to the indicator lights on the front and rear of the car.
2/ When the hazard switch is switched ON, the power supply from the ignition live feed is interrupted AND power from a secondary feed, which should be a permanently live supply, is substituted. This then sends power to the flasher unit and the pulsed (flashing) power is then switched to all 4 indicators, regardless of the position of the ignition switch.

Your M.O.T. tester is right: your hazard light should function independently of the ignition circuit, although it's usually an easy fix. You need to find the hazard with wiring and by a process of elimination work out which lead should be permanently live and connect it accordingly.
 
Messages
330
#4
If you're near to north London I'm happy to help for the cost of a few beers and a pork pie.....

Sorry, just realised you're in Northumbria.... so a bit far to be "just passing"!
 

johnjolly

Enthusiast
Messages
144
#5
Very kind thought and certainly one which I would have taken up.
I used to teach a lad who trained as auto electrician, I will search him out.
Incidentally I also taught the MOT guy and I don’t think he appreciated my help.
 

Melissa

Enthusiast
Messages
132
Location
France The Lot
#6
Your hazard switch has not been wired correctly and it's easy to fix. The hazard switch performs TWO functions when it's switched on.
1/ When the hazard switch is OFF the hazard switch is bypassed and power to the flasher unit passes from the power supply (an "ignition live" feed) through the hazard switch, to the flasher unit, the indicator switch and finally to the indicator lights on the front and rear of the car.
2/ When the hazard switch is switched ON, the power supply from the ignition live feed is interrupted AND power from a secondary feed, which should be a permanently live supply, is substituted. This then sends power to the flasher unit and the pulsed (flashing) power is then switched to all 4 indicators, regardless of the position of the ignition switch.

Your M.O.T. tester is right: your hazard light should function independently of the ignition circuit, although it's usually an easy fix. You need to find the hazard with wiring and by a process of elimination work out which lead should be permanently live and connect it accordingly.
just about to try & fix mine for CT thanks for this advice.
 

johnjolly

Enthusiast
Messages
144
#7
Andrew, I’ve just had a poke around and it appears I have live into the switch and ignition switched live. The ignition live works the hazards, but not the live feed.
I’ ve cleaned all the crud out inside the switch and I’m fairly certain that it’s not the switch itself that’s not functioning. Have you any other ideas?
 

Melissa

Enthusiast
Messages
132
Location
France The Lot
#8
I had to but a new part to get mine working, the little cylinder on the rhs footwell (can't remember the name ) flasher unit thingy, (rhs in lhd car that is)
 
Messages
330
#9
(I'm writing this after "a good evening out", so it might not make total sense...)

You've confirmed that there are TWO feeds to the switch; one permanently live and one "ignition live" only. As an opening gambit, trace where these two leads connect to the hazard switch and swap them over. Now see if the indicators work normally with the ignition off and the hazard lights DON'T work I would tentatively suggest the switch has a problem, although the switches don't normally fail. Try this first and report back. Will have a more considered (and less confused!) think tomorrow and I might offer more advice then.........
 

johnjolly

Enthusiast
Messages
144
#10
I’ve had switch out cleaned everything and reassembled, it works as it should on the bench and when fitted back in socket/holder in the car. Replaced the flasher unit. Still will not operate hazards on live power alone but does with switched ignition.
What puzzles me is that the same wire out of the switch, should carry power to flasher, either ignition switched or from fused live feed.
Exasperated and almost defeated.
And aren’t these R4 doors the most infuriating contraption, I had to tie it open to work inside! JJ
 

laxeian

Enthusiast
Messages
236
Location
Galicia
#11
“ And aren’t these R4 doors the most infuriating contraption, I had to tie it open to work inside! JJ “
:), I carry this for same purpose, its also cut to length that if put on seat crossmember and brake pedal it’ll lock the brakes ( my wheels have no centre hole to tighten driveshaft nut )
 

Attachments

Messages
330
#12
(More considered [=sober!] thoughts follow now...)

You've cleaned up the hazard switch & confirmed 2 things:
1/ The car's indicators work exactly as they should when the hazard switch is OFF, the ignition is ON and the indicator stalk is used to indicate left or right. GOOD!
2/ The hazard lights (all four indicators) DO work, but only when the ignition is ON-hence the MOT fail. Not good, but not disasterous!

I have 2 thoughts to run past you now.

1/ Does the lead that you believe is the permanently live feed to the hazard switch have 12 volts, as recorded by a voltmeter? Furthermore, are you sure it's not a lead which is earthing something else? If it WERE something which was acting as an earth for something it may well show 12 volts when a voltmeter is connected between it and earth, as the meter's resistance is very high, but cannot deliver enough current to power anything. A simple way to sort this is to wire an old headlight bulb between the lead and earth. If the bulb lights, you have a good source of current. If it doesn't, the lead is no good to power anything and you need to deduce what it IS for (but that's for another day!)

2/ Assuming the permanently live feed IS a decent source of current & can light a headlight, I'd suggest you remove the hazard switch from the dashboard and, using a decent voltmeter with a continuity testing (OHMS reading) option, do the following:
a) with the hazard switch OFF you need to ascertain the terminal on the switch to which the ignition live goes IN to the switch. Usually this is numbered "1". Using your meter, you need to find where the electricity comes OUT of the switch. It should be coming out of only one terminal, and that one is usually numbered "4" Check that no other terminals have any electricity coming out of them. This is how the switch behaves when it's OFF; the "ignition live" electricity comes into terminal 1, out through terminal 4 and then goes off to the flasher unit-the hazard switch does NOTHING!

b) With the hazard switch ON electricity should NOT flow through terminals 1 & 4-these 2 terminals should now be disconnected from each other. Two other terminals, usually numbered "2" and "3" are now connected to each other; Terminal 2 should have the permanently live supply running TO the switch from the battery (via a fuse) and terminal 3 allows the electricity to run FROM the switch to the flasher unit. If this wire has become disconnected or broken the indicators will work, but the hazards won't.

c) Now to the flasher unit: there should be FOUR leads running to & from it; 2 power sources-one permanently live and one switched through the ignition, and 2 pulsed or "flashing" signal wires; one powers the indicators when the hazards are off and one powers all four indicators when the hazards are on. When in the ON position the hazard switch breaks the normal (switched) power supply and substitutes the permanently live power AND diverts the pulsed power to all four indicators. Given your explanation of the problem I suspect one of the four leads running to the flasher has become disconnected or incorrectly wired.

Sorry to have gone on so long, but I hope all this helps!
 

mr-reno-139

AKA Paul Cunningham
Messages
2,011
Location
lancing west sussex england
#14
Depending on the age of the car you don't even need to have hazard lights working although if they're fitted i.e. the switch they must work
 
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