half an hour holiday (overheating)

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Still trying to figure out the wiring and finding all sorts of wiring horrors (and a lot of sticky tape)

But in terms of what is/was happening before the wiring diversion..

Prior to overheating the temp gauge would sit bang on the halfway mark, taken it across Europe before and it never really strayed from it.

Now, post thermostat change and coolant system fiush it idles at halfway mark but gauge soon rises with driving.

Idling (without having driven it) it took a good while for the radiator to get hot (10-15 minutes +) but wasn't putting any stress on the engine.

Yes thanks, engine held at 2000rpm while watching the header tank for bubbles.
LHD 1989 Diesel 1.7 somewhat homebrewed

Ads1987
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Re: half an hour holiday (overheating)

Post by Ads1987 »

How High is the gauge reaching when you drive?

bearing in mind you've mentioned you have a lot of wiring issues are you sure you aren't just getting a bit of a dodgy reading, the temp sender is only a single pin connector that relies on resistance to change position of the gauge. The fan is turned on by a separate temp reading at the rad itself, so if water wasn't circulating then I doubt the fan would reach temp to kick in.
I had a 1.7 d ky that had two cracks in the head and that was easy to identify because you could see the coolant header tank bubbling away at idle.

on your starting issue, are you getting any click or cranking or is it just totally dead?
1982 T25 1.9 DG model with 4 speed box

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Hi, thanks for pitching in!

Gauge hits 3/4 and after our last overheating episode tbh I haven't pushed it to see what happens. At this stage I can't rule out the reading being a bit 'keen', however before I changed the thermostat the needle always sat dead centre. I was planning to slowly troubleshoot it but then hit the non starting issue..

Currently no cranking, do get an audible click from the dash relay. Oil light comes on for a second when key is turned to first stop - had a few tries, on one I got yellow glow plug lights showing, other tries they didn't show. Wipers/indicators are working, put on just to confirm battery, multimeter across battery terminal measured 12.9v

And yes, the wiring is a can of worms I seemed to have inadvertently opened!
LHD 1989 Diesel 1.7 somewhat homebrewed

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

Pull the trigger cable off the solenoid and see what voltage you get when putting the key to the "start" position
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

Wiring diagrams in case you need them

http://syncrosport.com/info/wiring/

As an alternative to the starter solenoid you can also test the voltage at terminal 50 on the glow plug relay..... same switched live from the ignition switch
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Very sketchy connection at solenoid and spade terminal came straight off, looking at that now...
LHD 1989 Diesel 1.7 somewhat homebrewed

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

It’s alive!!! Brilliant, thanks so much. Sketchy trigger connection..

Now back to testing temps :)
LHD 1989 Diesel 1.7 somewhat homebrewed

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

Good.

Now you can use your meter to read what the resistance of the temp sender is and how that correlates to the gauge indication.

https://www.thesamba.com/vw/forum/viewtopic.php?t=464113
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Brilliant! Will be very useful and thanks so much for walking me through this.

Reading 10v across sensor wires so off to get some resistors..
LHD 1989 Diesel 1.7 somewhat homebrewed

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

The resistors are only needed for testing the gauge.

You can simply test what the sensor is giving with a meter set on ohms.

Check the resistance when cold. then warm it up until it reads on the half way mark and check the resistance there. Post back and lets see if that tells us anything.
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Ok, slightly puzzled how to do this..

Is it remove thermostat plug and use the multimeter across the thermostat terminals?
LHD 1989 Diesel 1.7 somewhat homebrewed

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

Correct.... except it's the temp sender terminals, the thermostat doesn't have any electrics
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

Thanks that’s what I meant of course, temp sender! Got thermostat stuck on the brain..

Was puzzled then as to how to watch when the gauge reaches halfway, or am I missing something

Cheers!
LHD 1989 Diesel 1.7 somewhat homebrewed

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937carrera
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Re: half an hour holiday (overheating)

Post by 937carrera »

Look at gauge

remove electrical connection

measure sender

refit electrics
;)
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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redsnapper
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Re: half an hour holiday (overheating)

Post by redsnapper »

So obvious when you say it!

Thanks :)
LHD 1989 Diesel 1.7 somewhat homebrewed

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