Re: turn signal flashers
Posted by HH56 On 2012/4/19 20:40:55
Here is a little comparison of today's model 535 flasher (NAPA NF535) which is supposed to be the direct replacement for our 6v flashers to an original Packard issue 6v model as used up till 48 - 49 timeframe. Electrically, the later 1950 on plug in types are identical except they go by 1,2,3 on the wiring diagrams instead of X,P,L. Did not look at a 12v version but expect it is the same electrically.
May have found the problem as to why some have issues with no indicator flashing. The replacements use a transistor to turn on the dash indicator. The old style uses a second contact which also appears to be thermally operated. It almost looks like a relay arrangement. Thermal closes a contact to bring in what appears to be a relay arm. Would have to fire it up to verify exactly how it is working.
Will be the first to admit my transistor theory was over 40 years ago, very basic and not used since then. One of you better electronics guys please feel free to contradict. The schematic as I believe it to be is shown.
The transistor appears to be a 9012 which lists out as a PNP. I believe the transistor as used is for a 6v negative ground and that may be the issue. It alone lights the indicator lights while the conventional thermal operates the signal lamps. When the thermal switches the signal light contact on it also is supposed to turn on the transistor but at what I think is reverse polarity, it can't.
One way to check would be to temporarily switch the battery and see if that theory holds -- but if the flasher has already been installed, the transistor may be toast.
Anyway, my two cents idea and probably only worth half that.
Attach file:
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May have found the problem as to why some have issues with no indicator flashing. The replacements use a transistor to turn on the dash indicator. The old style uses a second contact which also appears to be thermally operated. It almost looks like a relay arrangement. Thermal closes a contact to bring in what appears to be a relay arm. Would have to fire it up to verify exactly how it is working.
Will be the first to admit my transistor theory was over 40 years ago, very basic and not used since then. One of you better electronics guys please feel free to contradict. The schematic as I believe it to be is shown.
The transistor appears to be a 9012 which lists out as a PNP. I believe the transistor as used is for a 6v negative ground and that may be the issue. It alone lights the indicator lights while the conventional thermal operates the signal lamps. When the thermal switches the signal light contact on it also is supposed to turn on the transistor but at what I think is reverse polarity, it can't.
One way to check would be to temporarily switch the battery and see if that theory holds -- but if the flasher has already been installed, the transistor may be toast.
Anyway, my two cents idea and probably only worth half that.
Attach file:
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