MGB & GT Forum
73 MGB Hazard light doing funny things
Posted by Evansa69Midget
Evansa69Midget
Al Evans
Smyrna, TN, USA
Sign in to contact
|
Topic Creator (OP)
Jan 16, 2017 02:45 PM
Joined 8 years ago
130 Posts
|
73 MGB Hazard Light doing funny things.
Hazard light works fine in the on (Hazard Position). However, When the hazard switch is in the off position it will cause the red engine light to blink. This happens sometimes and sometimes not and will last for a few seconds to a minute. I've bought 2 hazard switches. The original burnt up and the 2nd one did too. So, on the 3rd hazard switch, I've hooked it up with console panel open. This is to check and see if the plug going to the switch was not overheating from some bad electrical connection. The plug doesn't get hot. So, I'm thinking the plug to the switch is fine. Not sure if its caused by the blinker box that makes the "dink, dink, dink" sound. All of this happens when the key is out of the ignition. I'm afraid that everything would go haywire is the engine was running.
Need help from an MGB electrical genius.
Thank You,
Al
Hazard light works fine in the on (Hazard Position). However, When the hazard switch is in the off position it will cause the red engine light to blink. This happens sometimes and sometimes not and will last for a few seconds to a minute. I've bought 2 hazard switches. The original burnt up and the 2nd one did too. So, on the 3rd hazard switch, I've hooked it up with console panel open. This is to check and see if the plug going to the switch was not overheating from some bad electrical connection. The plug doesn't get hot. So, I'm thinking the plug to the switch is fine. Not sure if its caused by the blinker box that makes the "dink, dink, dink" sound. All of this happens when the key is out of the ignition. I'm afraid that everything would go haywire is the engine was running.
Need help from an MGB electrical genius.
Thank You,
Al
RAY 67 TOURER
Ray Marloff
|
Jan 16, 2017 04:15 PM
Top Contributor
Joined 14 years ago
17,477 Posts
|
The design of this switch leaves much to be desired. If you never use the hazard flashers, it will never give you any trouble. However, once you use it, it tends to develop a bad internal connection. the switch is filled with dielectric grease and often, dismantling it and cleaning the contacts will bring it back to life. RAY
Jan 16, 2017 08:10 PM
Top Contributor
Joined 20 years ago
20,028 Posts
|
Although the hazard switch is a bit flakey (personally, I find it needs to be used more, not less) - but I can't think of why that would cause the ignition (alternator) warning lamp to come on.
Terry Ingoldsby
terry.ingoldsby@DCExperts.com
Terry Ingoldsby
terry.ingoldsby@DCExperts.com
Jan 17, 2017 07:03 AM
Joined 7 years ago
98 Posts
|
This is based on my understanding of UK models....The hazard switch performs two functions: when "Off" it passes volts to the regular flasher unit (from the fused green circuit) and hence via the stalk switch to the corner winkers. These are "usually" the top two contacts. When "On" if breaks the above circuit and provides volts to the 4 bottom contacts- left and right input and left and right output to the winkers. Physically the same switch but two different functions fed by two different circuits. The hazard circuit is fed via brown (in line fuse somewhere) to the hazard flasher and thence to the switch.
If the switch (or plug?) fails internally (you said it fried two of them) then the brown feed could connect in to the green circuit (albeit via the hazard flasher unit). Under normal circumstances, the green circuit is fed by the ignition circuit thru the ignition switch, . However if the green is somehow powered -in this case from the brown- you will energise the ignition circuit. This MIGHT cause the red warning light to glow as the hazard flasher flashes.
If you can find the supply brown to the hazard flasher unit or the ?light green and brown from the hazard flasher to the switch you can isolate the circuit. This may be difficult if it is a multi-plug. Can you trace the multi plug mini loom back to where it joins the main loom? By removing the hazard circuit you can see if the rest performs as it should.
If you can identify the 2 contacts that pass current to the regular flasher unit ?green "in" and green "out" you could connect these temporarily in the multi plug and remove the switch from the test. (However that only eliminates the switch, not the lead to the multi plug.)
None of this tells you why the switches fried. Either they were a faulty batch or there is a fairly major short to earth: or there is/are som very bad high rsistance connections causing excess current to flow and heat the switch. Switch terminals brushed against the edge of the hole in the steel dash would contribute....
If the switch (or plug?) fails internally (you said it fried two of them) then the brown feed could connect in to the green circuit (albeit via the hazard flasher unit). Under normal circumstances, the green circuit is fed by the ignition circuit thru the ignition switch, . However if the green is somehow powered -in this case from the brown- you will energise the ignition circuit. This MIGHT cause the red warning light to glow as the hazard flasher flashes.
If you can find the supply brown to the hazard flasher unit or the ?light green and brown from the hazard flasher to the switch you can isolate the circuit. This may be difficult if it is a multi-plug. Can you trace the multi plug mini loom back to where it joins the main loom? By removing the hazard circuit you can see if the rest performs as it should.
If you can identify the 2 contacts that pass current to the regular flasher unit ?green "in" and green "out" you could connect these temporarily in the multi plug and remove the switch from the test. (However that only eliminates the switch, not the lead to the multi plug.)
None of this tells you why the switches fried. Either they were a faulty batch or there is a fairly major short to earth: or there is/are som very bad high rsistance connections causing excess current to flow and heat the switch. Switch terminals brushed against the edge of the hole in the steel dash would contribute....
Forums
Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster