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1979 DT175 - electrical issues…

  • MikeK-uk
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1979 DT175 - electrical issues… was created by MikeK-uk

Hi there,
Now having some electrical issues, which seems normal!
When the engine is not running, should the headlight, indicators, horn work at all? Mine don’t.
All was working fine until today….
When engine is running, first symptom was indicators flashing double time. Thought that meant a bulb had failed, but all are flashing, albeit weakly.
Also instruments lights stopped working.
Headlight does not work, but “side / pilot” light and brake light do.
Obviously I can check the wiring for bad connections and bad earths, but wondered if my symptoms indicated a specific problem somewhere.
Also wondering whether I can ride the bike anyway, or whether I could end up broken down with flat battery?!
Any and all advice greatly appreciated!
Thank you.
Mike

 
01 May 2022 09:28 #1

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Replied by MarkT on topic 1979 DT175 - electrical issues…

Sounds like your battery went bad. 

Engine does not need a battery to run...  but lights won't work right as you are describing.  Not good to continue to ride with a bad battery. 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
01 May 2022 09:39 #2

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Replied by Gr8uncleal on topic 1979 DT175 - electrical issues…

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 from near Salisbury, Mike.

 
01 May 2022 09:48 #3

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Replied by MikeK-uk on topic 1979 DT175 - electrical issues…

 Hmm… battery is about 4 weeks old… maybe there is a problem with the charging system. Need to check that then.

And thanks for the welcome!

it would have been courteous of me to introduce myself. I live in the UK and wanted a DT when I was a kid. Many years later have had my ‘79 175 for about 5 weeks now. Really enjoy riding it, and problems such as this are to be expected, with mine being a survivor bike rather than something that has been rebuilt.
01 May 2022 10:19 #4

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Replied by MikeK-uk on topic 1979 DT175 - electrical issues…

Hmm… battery is about 4 weeks old… maybe there is a problem with the charging system. Need to check that then.

And thanks for the welcome!

it would have been courteous of me to introduce myself. I live in the UK and wanted a DT when I was a kid. Many years later have had my ‘79 175 for about 5 weeks now. Really enjoy riding it, and problems such as this are to be expected, with mine being a survivor bike rather than something that has been rebuilt.
01 May 2022 10:21 #5

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Replied by Pete-RT1 on topic 1979 DT175 - electrical issues…

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from Bracknell.
Hope you get the electrical issue sorted.
I love a DT175MX, my first bike aged fifteen.
Yamaha RT-1
Yamaha CT1-B
Yamaha CT1-C
Yamaha AT1-C
Yamaha CT3
01 May 2022 10:24 #6

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Replied by Gr8uncleal on topic 1979 DT175 - electrical issues…

Wait for other UK DT175MX owners to confirm, but I would suggest that lights should come on, even if engine not running (second position round on the ignition switch?).

It's probably worth trying to find a service manual for your specific model, as that will provide you with details of the wiring diagram, as well as the electrical components fitted and how to test them.
01 May 2022 10:43 #7

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Replied by MikeK-uk on topic 1979 DT175 - electrical issues…

So no load battery voltage was 4.9V with bike not running. Too low. The voltage collapsed when I turned an electrical load (bike still not running). Started bike to measure charging voltage… was 12.5V. So my guess is goosed regulator and a boiled battery?
01 May 2022 10:47 #8

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Replied by MarkT on topic 1979 DT175 - electrical issues…

It's possible I'm misunderstanding what works and when...  but if battery powered accessories such as indicators, horn, etc at least try to work, albeit weak, only with engine running it indicates the charging system is okay and somehow the battery is not supplying reserve power as it should. 

Could be a bad connection to battery but it's not uncommon for batteries to fail from vibration or just poor quality...  most aftermarket original types only have a 30 day warranty for a reason.  Yuasa Japan batteries are the ones I've had the best luck with...  or something like a Motobatt. 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
01 May 2022 10:55 #9

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Replied by MarkT on topic 1979 DT175 - electrical issues…

Your reply snuck in when I was posting. 

You might have blown some bulbs...  battery acts as sort of a rudimentary regulator which is why it's bad to run without or with a bad one. 

Make sure regulator (should be mounted on bottom left side of air/battery box, single yellow wire) is connected and has a good ground wire attached to one of the regulator case mounting bolts.  I've seen a few where regulator ground wire is missing which makes regulator useless. 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
01 May 2022 11:02 #10

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