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TR4/4A Flasher Unit...VERY hot

ghawk16

Jedi Trainee
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So was doing some double checking on wiring today on my 63 TR4. The White/Red wire fell off my starter solenoid yesterday and car wouldn't start when out yesterday. I panicked a bit but started it bumping the solenoid and fixed it today. Played with my light switch and got the running and headlights working, finally! Swapped some grounds that I incorrectly hooked up...all dash lights now work correctly! However, when trying to get the the turn signals to work I hit the stalk on the steering column and then heard a click spaced out by another click but no turn signals and no blinking green light. Confirmed everything was wired correctly to the flashing unit, light, stalk etc. Unplugged the flashing unit to inspect, then plugged it back in to see if it would work. Well I could smell something burning and wasn't sure what it was. So I turned off the blinker and then I touched the flasher unit and burned myself quite nicely. The burning smell was the flasher unit close to the windshield washer hose. Could the flasher unit be bad? Wrong bulbs in the turn signals? I used the bulbs from the TRF bulb kit and matched them up to what was in there previously. Thoughts? Just glad I have my running lights and headlights working now as most people don't use their signals in CA anyway.
 

TR3driver

Great Pumpkin - R.I.P
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What are you using for fuses?

If the flasher wasn't bad before, it certainly is now. But before replacing it, I might try to safely measure the load current, to make sure there isn't some other problem. If you use an ammeter to bridge G to GN at the flasher (flasher removed), you should get zero with the key on but the turn switch off; then close to 4 amps with the turn switch in either left or right turn.

Its probably best to install a smaller fuse while making this test, so your meter doesn't get damaged if there is a short. Some meters have an internal fuse, but its a lot more expensive than a box of AGC 5.
 
OP
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ghawk16

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I will do these tests tonight. Im running a 10A fuse in the red and 15A in the green. Was going to buy some British fuses from TRF but may just go to Napa and get some 15A and 20A fuses and bump each one of those up 5 amps.
 

Sarastro

Obi Wan
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Hot components means high current which means a short circuit somewhere. If you can't work on it right away, it would be a good idea to disconnect the battery.

Since the flasher has self-immolated, it seems clear that the short is somewhere in the turn-signal circuit. It shouldn't be that hard to trace it. My guess is that a wire came loose and is touching something it shouldn't.
 
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ghawk16

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Well I tried measuring the G to GN with amperage and got 0 with key on or off and turning switch up or down. So I unplugged the switch underneath the dash and measured resistance on green/brown then green/red and green/white. Well, I measured a closed loop on both no matter which way the switch was so I think it was shorting out. So I ripped out the switch, cleaned the contacts, measured and all came out OK. Reinstalled the switch and measured again to make sure all was still good. Measured green/brown from flasher unit connection to connection at switch albeit short, all good. Measured the red/green wire at connector under dash to the center pin/contact at the rear blinker light and it showed closed. Now if someone can confirm this and I'm sure it's supposed to be this way, but when I touched the center pin with my multimeter to the housing it showed closed. So essentially the bulb completes the ground and when you turn the switch at the stalk it grounds one side and goes back to the flasher unit. Well, I'm hoping that my switch being grounded on both sides over worked the unit and that's what caused it to get hot. I'm going to order a new flasher unit from Moss since it'll get here quicker and hope that works!!! Any other ideas?
 

TR3driver

Great Pumpkin - R.I.P
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I'm a bit confused by your description; but an unlit turn bulb is fairly low resistance and looks more or less like a direct connection to ground. That was why I suggested measuring current (bulbs lit) instead of resistance.

Turning the switch connects the output of the flasher to the bulbs on the relevant side. The bulb in turn connects to ground, which completes the circuit back to the battery.

When the bulb lights up, the filament (which is now glowing white hot) goes up quite a bit in resistance. I forget the exact numbers offhand, but it's something like 1 ohm dark and 6 ohms lit.
 

TR3driver

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Hot components means high current which means a short circuit somewhere.

Not necessarily. A higher than normal resistance (bad connection, or dirty contacts) can also make a lot of heat in places that don't normally get hot.

Plus of course, the standard flasher works on heat, so it normally gets somewhat hot in operation.
 
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ghawk16

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I'm a bit confused by your description; but an unlit turn bulb is fairly low resistance and looks more or less like a direct connection to ground. That was why I suggested measuring current (bulbs lit) instead of resistance.

Turning the switch connects the output of the flasher to the bulbs on the relevant side. The bulb in turn connects to ground, which completes the circuit back to the battery.

When the bulb lights up, the filament (which is now glowing white hot) goes up quite a bit in resistance. I forget the exact numbers offhand, but it's something like 1 ohm dark and 6 ohms lit.

Yeah...sorry...you summed up what I said, However I didn't measure resistance across G and GN, I only measured amperage and couldn't see anything. I didn't measure resistance across G and GN like you mentioned above, but will tonight with key off of course. For some reason I didn't do that. I honestly think it was something with the switch shorting somewhere.

A new flasher unit and horn brush are on their way from Moss so I should be able to get the horns working too. I broke my brush accidentally...fragile in its old age. One last question...does the small ball bearing go against the ring down in the steering wheel or against the horn push button. I forgot the orientation and Moss doesn't show it.
 
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ghawk16

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OK...checked resistance on the good 'ol ohmmeter and at no flick of the turn signal switch I was at 0 and at any turn it bumped up to 4. So hoping we will be good when the new flasher unit shows up tomorrow. <crosses fingers> Thanks everyone!
 
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ghawk16

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Well new flasher unit is in and turn signals work, kind of. They are very dim and don't blink well. Plus, when the blinker comes on the red light in the dash blinks ever so slightly and NO blink from the green. The light green/violet is coming from the flasher connector to the middle terminal of the bulb holder (using OE since the updated harness didn't come with new holders) and the outer is going to a black wire in the harness. My red light works correctly when the key is turned on and has the brown/yellow going in and white going out. I checked voltage when blinkers were on at the light green/violet wire connector near the bulb and got random readings. Now I'm stumped.
 

TR3driver

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Sure sounds like there is still a short somewhere, maybe not to ground; plus perhaps some bad connections. I'm thinking maybe the dash indicator is shorted to something, and when the flasher tries to light it, the extra current is sucking down the voltage in the white circuit (hence the change in the red light). Short duration plus current limited by bad connection means the fuse doesn't blow.

I would probably proceed by checking the voltage on the green wire, at the flasher.
 
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