Diagnosing Temp Gauge Fault

[Bluest]

Im sure this must have been covered before but I've had no luck with the search. What is the process for diagnosing a faulty temp gauge. I guess the fault will either be the sender, the gauge itself or the wiring in between. I have a multimeter so it can't be that hard, can it?

I guess I need to check the resistance of the sender, but what values do I look for? And where is the sender on an F14D?

If the sender checks out, how do I check the gauge?

 

[winston1]

The sender on the F24 is right below the thermostat. Don't know about the F14. A simple test just to see if the sending unit is working at all is to check continuity cold, then crank and see if it changes. If not, the unit is bad. I suppose you are confident you are getting a bad reading?

 

[murphy1244]

To test gauge touch sending wire to ground while someone else watches the gauge. It should peg to max, do not do this test alone you need to touch it and stop or you short out the gauge.

 

[Bluest]

The sender on the F24 is right below the thermostat. Don't know about the F14. A simple test just to see if the sending unit is working at all is to check continuity cold, then crank and see if it changes. If not, the unit is bad. I suppose you are confident you are getting a bad reading?

I'm pretty sure something is wrong, the gauge never moves off cold.

What do you mean by "crank"?

 

[winston1]

I'm pretty sure something is wrong, the gauge never moves off cold.

What do you mean by "crank"?

Start the engine and watch as it warms up.

 

[Bluest]

Start the engine and watch as it warms up.

Cool, thanks. Tempted to pull the sender out and do it with a pan of water.

 

[normde2001]

What murphy said for testing gauge, although no need to worry about shorting gauge. If gauge works, replace sender.

 

[Bluest]

Gauge shot right up when I touched the wire to ground. So I guess the sender is goosed. The hunt begins. Need to measure length, thread etc to see if I can find an equivalent match over here.

 

[winston1]

m16-1.5

 

[Bluest]

m16-1.5

You've got to live this place! Thank you Winston!

 

[California]

Tip that might narrow down the search - I would start by looking at Japanese car models the same age or a little older. At least for the older Yanmars, they shared Hitachi etc electrical components with whatever cars were widely sold just before that Yanmar model was introduced.

There's no reason for Yanmar to invent a new temperature monitoring system when they could contract for existing components that are already manufactured by the literal millions.

 

[normde2001]

Check '72 Nissan 510, 620 sender. It looks like what Hoye, (USA) stocks, and Yanmar used a lot of '72 Nissan parts.

 

[Bluest]

Tip that might narrow down the search - I would start by looking at Japanese car models the same age or a little older. At least for the older Yanmars, they shared Hitachi etc electrical components with whatever cars were widely sold just before that Yanmar model was introduced.

There's no reason for Yanmar to invent a new temperature monitoring system when they could contract for existing components that are already manufactured by the literal millions.

Thanks. I spent last night trawling an online parts catalogue. There are a lot of senders that have the same thread and terminal. I've not seen any that have the same 22mm hex on top, they are all 17mm or 19mm, but I'm not sure if that matters. Also do they all have the same resistance properties? If it physically matches, does that mean it will work?

 

[Bluest]

Check '72 Nissan 510, 620 sender. It looks like what Hoye, (USA) stocks, and Yanmar used a lot of '72 Nissan parts.

Thanks. I Googles that, but it brought up examples that werent threaded.

 

[normde2001]

Thanks. I Googles that, but it brought up examples that werent threaded.

????
Wells Vehicle Electronics Temperature Sending Unit TU62: Search no more for the best Temperature Switch/Sender at Advance Auto Parts

 

[California]

That one looks about right but it might only output yes/no overheat for a warning light application, rather than variable resistance to drive the needle proportionally on a gauge. Maybe verify that the recommended applications had gauges instead of lights.


Not relevant here but I once read that Ford's gauges don't really indicate proportional temperature - just various broad steps: Cold, Warming up, OK, Too hot.

 

[Bluest]

????
Wells Vehicle Electronics Temperature Sending Unit TU62: Search no more for the best Temperature Switch/Sender at Advance Auto Parts

Thanks. That looks a lot more like it. I guess Google feeds us Brits second rate results!

 

[Bluest]

That one looks about right but it might only output yes/no overheat for a warning light application, rather than variable resistance to drive the needle proportionally on a gauge. Maybe verify that the recommended applications had gauges instead of lights.


Not relevant here but I once read that Ford's gauges don't really indicate proportional temperature - just various broad steps: Cold, Warming up, OK, Too hot.

Noted. I think I'll just get one to try. As my cooling system seems to be functioning correctly, it should be obvious if the sender isn't right.

I'll match your not relevant with my own. I understand that modern cars have their gauges programmed to sit in the middle of the range and only shoot up when they is a problem. Stops the dealers being hassled with "my cars running a bit warmer than my mates" etc.

 

[normde2001]

That one looks about right but it might only output yes/no overheat for a warning light application, rather than variable resistance to drive the needle proportionally on a gauge. Maybe verify that the recommended applications had gauges instead of lights.


Not relevant here but I once read that Ford's gauges don't really indicate proportional temperature - just various broad steps: Cold, Warming up, OK, Too hot.

Specs say for gauge.

 

[California]

Specs say for gauge.

Great! I'd buy it.