Hi from UK
Bought a barn find dt175c US spec which has most of the wiring loom there but ignition switch is missing There is a 4 pin connection block spare which presume was where the ignition probably plugged into . CMSNL website shows a 4 pin plug for the dt1c because they don't have dt175c   but looking at the  parts catalogue  I have  for the bike it  shows the ignition switch with a 4 pin connector plus 4 more wires coming out of it. Does anyone have a wiring diagram for dt175c.
Julian

Up at the top of the page, tech library, have a look thru there for your bike. Sooo much info in there.

I'm fairly certain the wiring diagram is in the Tech Library.

US model DT175 starting in 1974 had the headlight/taillight controls moved to the handlebar switch compared to the older CT models.  The DT175 ignition switch has just four wires... 

Black and Black/white are "ignition kill", connected with switch "off", and not connected with switch "on".

Red and Brown are "battery power".  Red (from battery) and Brown (powers accessories) are not connected with switch "off" and connected with switch "on". 

I might be wrong about this but I'm pretty sure it's the same ignition switch as used on the DT175MX (monoshock) model until at least 1981 so should be easy to find a new aftermarket (aka pattern) switch in the UK

Hi Sneesles and  MarkT 
Thank for the replies Found the wiring diagram but on my computer it's very small I but  can work with that. I think I was getting fixated on the parts catalogue drawing showing more wires but the wiring diagram makes more sense. 
Thanks 
Julian 

Looked on ebay and they show a 9 pin switch for 175c model . the colours are yellow, white, yellow/white red/orange, brown, red, blue/brown, black/white, black.
Was the c model only sold in US. There are 4 pin switches available  but they don't include the c model in description. Not sure where all the other wires would go anyway
                                                                                                                                                                                                                                          

 from near Salisbury, Wiltshire.

I've no idea why the 1976 DT175C online parts list is missing from CMSNL. However, Partzilla shows it as having the same ignition switch part number as other models  - CMSNL show as having one in stock (see link). Interestingly, Partzilla also have the same "wrong" diagram.

MAIN SWITCH ASSY for DT175 1975 USA - order at CMSNL

 

You have the diagram and the wire colors.  Diagram and my post above describes the operation of the switch.  You can take a pic of your 4 wire connector and the switch mounting and compare to the very common switches available I already mentioned.  Yamaha used similar parts across every model they could.  I'm pretty sure for the US DT175 the same ignition switch was used from 1974 to 1981... 

Or you can rely on ebay seller listings which are often completely wrong and keep searching and buy a switch that they "say" is correct even though it doesn't match your bike at all.  Your choice.

I alluded to what the extra wires are for...  the LIGHTS.  If you have a model that had the on-off for the lights controlled by the key switch, it has several more wires.  If you have a 74-76 USA DT175, the on-off for the lights is in the left handlebar switch and the key switch has 4 wires.

Parts diagrams are not assembly diagrams...  they are artist renderings that often, but not always, accurately depict the part and the location.  Many people have assembled their clutches incorrectly, for example, by following a parts diagram that does not show the parts in the correct sequence.

P.S.  Your USA DT175C model is a unicorn in some respects.  While it appears to be nearly identical to the US DT175 74-75 twinshock models, 76 has a different frame, tank, and seat.  The engine (primarily the clutch/transmission) also has several significant internal changes from the 74-75 models as well...  even though they look similar from the outside. 

Thanks for that Mark. I've ordered the four pin switch and thank you for the explanation. It makes sense now.

I'm late to the party & not much help but if you haven't had it up & running yet it will run without the switch.
Just devise a way to stop it incase of a stuck throttle or similar.
I guess ya way ahead of me but look forward to hearing & seeing how she runs.
Cheers from NZ downunder.