Club 80-90 Forums

story so far......

1900 Water Cooled 1986 T25

temperature gauge has never worked since I owned it.

changed
1) pcb
2) temp gauge
3) temp sender unit

tested
1) 12 volts across temp. sender plug in engine bay
2) both temp gauges move up if connected directly to the plug in engine bay.
3) disconnecting earth point under coil (which looks rubbish) make no difference to campers operation, connecting to engine earth point also make no difference. (does this earth point do anything?)

understanding of curcuit (thanks to grun last time I looked into this)
1) 12V+ goes into PCB through the temp gauge, down to the sender unit and to ground under coil.
2) the connector on the pcb socket of temp gauge is 6 or actually 4 if you like due to them being linked

confusions
1) if my understanding of the circuit is correct then disconnecting the earth point under the coil should mean I no longer have 12V at the sender plug but I still do?
2) I am surprised that any of the minor electrical devices in the engine bay work at all with the earth point disconnected?
3) if I bypass the plug then you can hear the engine labouring due to the current draw on the alternator, but what could be drawing enough of the current?


possible reasons for opinions or advice
1) what about if someone has put the wrong wire into position 6 on the socket and the sender unit is actually joined up to for example the battery warning etc etc?
2) is it possible to find a short circuit in the engine bay as I need to discover how it is possible that the circuit can be completed if I have one end of it 6 inches away from any metal.

clartsonly wrote:story so far......

1900 Water Cooled 1986 T25

temperature gauge has never worked since I owned it.

changed
1) pcb
2) temp gauge
3) temp sender unit

tested
1) 12 volts across temp. sender plug in engine bay
2) both temp gauges move up if connected directly to the plug in engine bay.
3) disconnecting earth point under coil (which looks rubbish) make no difference to campers operation, connecting to engine earth point also make no difference. (does this earth point do anything?)

understanding of curcuit (thanks to grun last time I looked into this)
1) 12V+ goes into PCB through the temp gauge, down to the sender unit and to ground under coil.
2) the connector on the pcb socket of temp gauge is 6 or actually 4 if you like due to them being linked

confusions
1) if my understanding of the circuit is correct then disconnecting the earth point under the coil should mean I no longer have 12V at the sender plug but I still do?
2) I am surprised that any of the minor electrical devices in the engine bay work at all with the earth point disconnected?
3) if I bypass the plug then you can hear the engine labouring due to the current draw on the alternator, but what could be drawing enough of the current?


possible reasons for opinions or advice
1) what about if someone has put the wrong wire into position 6 on the socket and the sender unit is actually joined up to for example the battery warning etc etc?
2) is it possible to find a short circuit in the engine bay as I need to discover how it is possible that the circuit can be completed if I have one end of it 6 inches away from any metal.

My 1986 T25 water, 1.9. The temp gauge stops working when I turn the lights on. Doubt that helps but how the lights can affect it I don't know.

Eh....
If you earth out the wire that connects to the sender, the gauge should go full scale and the red light flashes.. earth it on the engine next to the temp sender.. if the gauge moves and flashes then it must be the sender unless for some strange reason the circuit in the gauge is faulty... (but you have changed it..)
where is the sender mounted?

ther is also a large wire fron the nose of the gearbox connected to the chassis..

If you have a large current draw from disconnecting a small earth wire then you would have had a fire already.. its prob more to do with the poor earth affecting the ignition circuit..

My 1986 T25 water, 1.9. The temp gauge stops working when I turn the lights on. Doubt that helps but how the lights can affect it I don't know.

that does sound like a generally bad earth, check the castle earth points behind the fuse box.

I am not fully sure what you want me to try toomanytoys?

if I put solder between the two pins on the sender it is drawing something as the engine note changes where the alternator is working but does not affect the dash, if I put a temp gauge between the two pins it goes slowly up to about 3/4 hot. these tests do not change whether I have the earth connected under the coil, disconnected completely, or attempted to be connected to an engine bold already used as an earth.

tomorrow I will photo the offending earth point, as you will notice it is the equivilent to finding a piece of wood and using that as an earth point with some rusty wire and sellotape. everything else (which I wanted to work) works now including changing gear without needing to borrow geoff capes.
but I do not want to be deafeted by this, I have most importantly driven 100s of miles without topping up the expansion tank (fingers crossed), it starts on demand with the power of a new starter motor and I keep it at the correct amount of oil that it only drips once in a blue moon out of the araldited drilled through push rod tube, I want to know if it is happy hot or cold, I use the heater to work that out currently

it is as if (if you look at my bold highlighted ponder) the temperature sendor unit wire is not even going to pin 6 and when I am short circuiting it is simply completing some other circuit, perhaps if I hear the sink taps start it means that it is too hot in the engine bay

if I am right a good earth point will show very little resistance between one eg under the coil to another eg the engine? if I disconnect the wires from under the coil would this be a good test?

something that struck me as i read this thread..........
if the gearbox nose earth is good, and the connection between the bellhousing and the engine are good, and the connection between the sender and the wire are good, the earth near the coil will make little or no difference, as the other earths are dealing with it........ however, the earthpoint near the coil is only as good as the end that connects to the head and the loom........

have you tried running a fresh rest wire from the sender to the dash, missing out all the junctions alog the way? that where i would go at this point.........

Right.. what sensor are you linking the wires out on?
yours is an early cooling system (1985) so the temp sensor is a single wire going to the sensor on the thermostat housing.. disconnect and touch this wire (earth it out) on the engine.. the red led should flash and the temp gauge should go full scale... if it doesnt do that then there is either fault with the wireing (so run a new wire to the dash or there is a fault at the dash end..... it doesnt get simpler than that...

the only thing you can link out (thats got 2 wires in it) is the level sensor on the pressure tank, this is NOT a temperature sender...

no mine is a new type 1986 (my profile is wrong). to blue sender unit

the sendor has a socket with 2 pins on it, I am merely pushing a single piece of solder into each hole in the socket to short the circuit, and water level sensor is in the expansion tank, I am dealing with the thermostate housing, I know that as the backs of my legs hurt from leaning over so much. Wait until I have some photos it is possible that all of a sudden someone will say arrhhh its a blue one; do this.

Right... that explains why I was confused about it.. (update your profile )

85 can be either anyway......

right then... some pictures and explanations and at the bottom a couple of comments after pulling some wires out of the box which may help.

(sorry about the artistic look the camera was on some fancy setting)

earth point under coil
[img:800:600]http://clartsonly.com/camper/img_0056.jpg[/img]

thermostat housing (just so we know what we are discussing)
[img:800:600]http://clartsonly.com/camper/img_0057.jpg[/img]

the two pin plug
[img:800:600]http://clartsonly.com/camper/img_0058.jpg[/img]

almost 12 volts, the ignition is on 2 the engine not running
[img:800:600]http://clartsonly.com/camper/img_0059.jpg[/img]

as you can see no earth, rubbish bolt and still 12 volts
[img:800:600]http://clartsonly.com/camper/img_0060.jpg[/img]

after a few minutes the temp gauge only reaches 3/4 full no flashing light, which does make me wonder that there is not quite enough.
[img:800:600]http://clartsonly.com/camper/img_0062.jpg[/img]


TESTS COMPLETED.
1) the earth point does work between the rusty old hole and the earth point on the engine, that reduces right down.

2) I opened the electrics box on the left and could not find a brown/black wire even though there is on joined to the senders socket?

3) I did find what appeared to be the black wire and confirmed this by checking the resistance between the socket and the wire, this went down to a couple of ohms (rubbish multimeter), BUT I also checked the other side of the socket against the same black wire which read 100 ohms, so this is surely a short where the positive is somehow going to earth too?

4) I tried to remove the relay but it felt as if it had melted in to its holder where a purple/black wire was going into it?

5) If I bypass the socket with some solder the camper van will not start because of the loading on the alternator.

I need to use the camper on saturday so will need to leave it until after the weekend, but I do feel this is an electrical fault and have left the socket unplugged, when I purchased the Van the previous owner said he had fixed a load of the electrics because it had burnt out, maybe this bit had not been fixed.

no ideas?


I will strip the outer of the wires and discover the exact journey of these wires.

If linking out with solder and thats all you have done and you say the load on tha alt is too high, where is it going?... the solder would blow pretty quick and if it didnt the wires you linked out would soon burst into flame..
I dont think the alt could be loaded enough to prevent the engine starting..

What continuity do you have from end to end on those wires? (dash to sender connection)

the solder would blow pretty quick and if it didnt the wires you linked out would soon burst into flame..

that is what someone else at work said, which is why I have disconnected the socket completely now.

he also suggested that maybe the second pin is for the overheating light and both wires go to earth on their own circuits? Although I assured him that the electricty flowed through the sensor and out through the other wire as boats do. I assume I am right?

I will have to undo the wiring loom to find the ends and do a continuity test.

*sigh*
ill say it once more.. just incase.
the flashiing red light takes its signal from the temp gauge at the dash end, AND the low level sender in the header tank,

the sender is plastic, and plugs into a plastic thermostat housing, therefore it must have two wires, as it cannot connect to earth any other way, one wire is "live" and one is Neg. If they are damaged, or mented together, buth will be one, or the other and not do their job.

i would say the not starting thing when the wires are bridged is more to do with taking the live feed away from the coil than anything else.......