Directionals Suddenly Wonky...Relay?

[OK-944]

The directional signals on my '87NA are suddenly very inconsistent in both directions. The left turn signal, which was previously very consistent and even, now blinks really fast - and the right is variable.

Fuses are fine...so my guess is a wonky relay. Sound about right?

[wwdwgs]

Check the light bulbs of the side where the blinker quickly flashes. Burnt light bulb filament causes the flasher work faster.

[Monkey Wrench]

"Burnt light bulb filament causes the flasher work faster."

- I think that's actually backwards..



if resistance is lowered, current flow increases, then the bimetallic strip in the flasher relay heats up faster. so it blinks faster.
higher resistance means a slower blink rate, less current.

I think if a bulb is gone out then its going to increase resistance as the others are in parallel,,

thik of it this way :
if you add more bulbs in parallel the total resistance is lower with additional circuits being added in parallel .. if you lower resistance you increase the current, increased current flow makes the bi metallic strip heat FASTER.

bad grounds are often the culprit, a bad ground will also increase resistance, and lower the current flow , making the bi metallic strip blink slower. if it blinks too slow first thing Id do is check for dirty contacts and ground points.

a dirty ground will increase circuit resistance, lowering current flow, and lowering the blink rate.

id check bulb sockets and pins, clean them and check the ground near each lamp as well, you can use a meter to compare left side resistance to right side resistance. if one is lower find out why. check the ground resistance with reference to battery negative.

the wrong bulb can cause this so check if they are the correct bulb it can also cause melted lenses.

flasher contacts may become pitted and dirty, .. change it , or clean contacts.

some add LED's, but fail to keep the resistance the same. I think if you swap to LED's you can increase current flow to spec by using added resistors in parallel with the load, to avoid reducing the current flow, so the bimetallic strip heats at the original rate.

LED blinkers aren't a good way to save fuel or reduce alternator load, because they are in use so little of the time. if you like them for other reasons, you can add resistors to maintain the original current flow.

You can perhaps modify the blink rate with a different type of blinker relay. I don't see that mod as worthwhile.

I just bought 6 brake light bulbs from rock auto.. well I thought it was 6 bulbs, but no, instead I received 6 boxes of 12,, incredibly cheap..
I guess they are unloading stock so I got enough bulbs for a lifetime for a cost of around 3 bucks lol.. fill your boots, great stocking stuffers too lol.. no excuses for re-using dirty old ones now..

[azbanks]

You can get a relay for LED bulbs and then you don't need to worry about the resistors.

[Jfrahm]

I think the circuit is a current divider and the flasher is one of the elements. With 2 bulbs and the flasher the current is split 3 ways. If a bulb goes out the current is split 2 ways and the amount seen by the flasher goes up. Thus you get a faster flash as the flasher gets more current to dissipate, heats the breaker strip faster, breaks the circuit more often.

OP probably has a bulb out or a bad socket.

[OK-944]

Its been awhile since I've cleaned those contacts - so this makes perfect sense...thanks! But right now outside temps. are hovering around 10F...maybe a bit warmer in my garage - but that metal is still just a bit frosty!

[Monkey Wrench]

the front and back flashing bulb , on each side are in parallel with the other bulb on the same side of the car. if they were in series if one went out it would take the other out too. that's not the case.

if you have two bulbs in parallel and one goes out the electrical load on that circuit is reduced. If bulbs are the same, and one is burned out, that circuit through , the two and the flasher is carrying half the amps, still 12 V. the good bulb will burn at full intensity.

the flasher has a bimetallic strip and it is in series with the load of two bulbs, reducing the load by a bulb being out will cause the flasher to run slower as it is carrying a lower amp load, so it takes longer to heat the bimetallic strip to the point where it disconnects the current ( as it flashes)

if one has a bad ground, same thing , then that circuit is carrying less current because the current load is then reduced due to increased resistance of the bad ground. the bulb with the bad ground may glow dim since its is sharing it's load with the resistance of the bad ground which is then in series with that bulb.

under the bad ground condition the bulb would have less than 12 V because some of the load is being used by the resistance of the bad ground. so as an example you may have 6 V or voltage drop across the bulb which is fine, the current is reduced because the resistance of the bad ground is added,

you could then measure ( as an example) 6 V across the bulb, which is glowing but dim,
and 6V between the ground side of that bulb and a clean ground.

under that example if you shorted that ground wire to a clean ground ( correcting the issue) it would remove that resistance and the bulb would burn brighter and the flasher would speed up..
Removing the bad ground removed resistance from that circuit , thus increasing it's current..
the bulb then burns at normal brightness because it is no longer in series with that added resistor( the bad ground)

increasing the circuit resistance through the bad ground lowers the amp load. the amp load is in series with the bimetallic strip.

of course in a practical sense the bad ground would not be sharing the load evenly at 6V of drop but it would be some load in series with the bulb.. the bulb and the resistance of the bad ground are in series and the resistwnce through the two is greater than only the bulb itself.

increased resistance means the circuit is carrying a lower amp load. a lower amp load heats the bi metallic strip more slowly so the flasher slows down.

If you see a dim bulb, and the flashing seems slower on that side, check it's ground point and clean the socket.
I think the bad ground scenario or bad contacts in the bulb socket would be my first checks.




- yes its possible to change the bi metallic strip and now the circuit is using less amps and all is well, so long as al the contacts are clean..

the problem that I can predict then is that the same bad ground situation will become even more of an issue because now a bad contact ( added resistance by dirty socket or ground) the circuit will then have less ability to overcome the situation as there are less amps..

it will work so long as everything is clean but It will become more sensitive to things like bad grounds as there isn't as much current available in the circuit to share.

if the reason to add LED bulbs is to increase brightness and the bulbs have resistors in paralel to make them have the same current draw as OEM bulbs , I like that better myslef.

the power savings are so minute that this is not really helpful.

, with headlights it may be significant but flashers are in operation such a low percentage of driving time that its a very negligible power savings.

so while ethe flasher will work with a smaller bimetallic strip and low amp bulbs , so long as all the contacts are clean and have no resistance, Id still want to
keep that original by using bulbs with resistors that match the OEM current draw.. and keep the flasher itself OEM.

the mod works eclectically, but I believe there is some drawback because makes the car a bit more susceptible to issues caused by any contacts that are not perfect.




Anyway that's how I see it, if I'm wrong feel free to correct me.
Phil

[Monkey Wrench]

I saw a kind of similar issue in my van. I was buying fuses and found there are a new kind that has a small LED,, the idea is that if the fuse blows, the LED lights up so you can find it.. neat I thought so I stuck one in my cigarette lighter circuit..

I was using the lighter circuit to power a USB thing for my phone , it has an LED on it..

next the LED is on, indicating I have power for my USB outlet. but my phone wont charge.. weird..

finally I realize that what is happening here is the fuse blew, but because it has a little LED to indicate that it is blown, it is still actually conducting a tiny amount of current through that LED.. which is in turn enough to light the led on my USB adapter.

my lighter is in parallel with it so it's LED is also on.. now its fooling me because its indicating it has power, but there are almost zero amps available because the fuse is actually blown.
if I used my meter it would still indicate 12 V, sure it has 12 V it just has about zero amps available.
the digital multi meter is sensitive so it senses 12V, but there isn't enough current available to light a light bulb. this is an example of where "erroneous readings" can throw a guy off course.. if I were instead to use a test bulb it would show no power, even though the digital meter can indicate 12 V..


The lamp is on on the plug in thing with the usb,, but it won't charge the phone.

they might not make that type of fuse for the euro style fuses.. I decided I won't use them again. If I use a normal fuse and it blows then the LED on the USB thing that's plugged into the lighter socket would simply go out.

the LED's do have some advantages, they are brighter and use way less power. the problem as I see it is that this also means that any tiny bit of resistance can mess things up , it will turn the LED off.. whereas something like a connection which is a bit less than ideal will still operate.
an example of it still operating is that a bulb may glow but a bit dim because it is effectively in series with a bad ground or a socket that is a bit dirty.

the higher current of an incandescent circuit is more forgiving with respect to the added load of a dirty connection.

with brake lights maybe a good option is to add an LED leave all else original but use the spare socket in the tail light lens for an added LED.

my 89 volvo also had that spare unused socket in the tail light lens so I did that, it increased the brightness of my brake lights. adding that LED bulb increases the brake light load but the draw is not huge, so I never needed other changes there.

I think the same can be done to a 944 if it also has that empty socket.. might as well use it? I don't think you'd want the added resistors there ,since its in parallel with the OEM brake light bulb.