Technical Opening in fire-wall

[ernibv]

Another strange question: I want to pull a wire from the engine bay through to the cock-pit. I want a test-led to show me when the fan is running.
Not when the relay is activated or the fuse is supplying power. Just real info right from the fan connection. Red LED with 560 ohm resitor. Much to my surprise I cannot find even 1 little hole. The b is really well insulated. Any ideas ?
grtz

 

[wapper]

Who needs a hole in the firewall, if you don't have a roof )

 

[Bobs2293]

Another strange question: I want to pull a wire from the engine bay through to the cock-pit. I want a test-led to show me when the fan is running.
Not when the relay is activated or the fuse is supplying power. Just real info right from the fan connection. Red LED with 560 ohm resitor. Much to my surprise I cannot find even 1 little hole. The b is really well insulated. Any ideas ?
grtz

Why would you want to do this? You can hear if the fan is running.

 

[ernibv]

The question is 'how', not 'why'.

 

[turining]

The question is 'how', not 'why'.

In a way the question is why.
It depends on if it's going to be permanent or temporary.
If it's permanent - then don't know the answer.
But, if as you question infers ("I want a test lead") it is temporary, then run it externally.
You would only need one core of a ribbon cable, so no great size, and earth it inside the car.
However, just because the LED lights up does not mean the fan is actually running/turning, only that it has current to do so.

Any way - the best of luck.

 

[ernibv]

Thanks. That's what I ended up doing. I want an accurate meaure of when the thermostat opens, so I have a small digital meter tie-wrapped to the intake just in front of the wipers. The idea is to also have a LED from the fan, which does work. It's just difficult to tell when

 

[s130]

Why not just let the engine idle till the fan cuts in and out. You can take/monitor the water temperature whilst your head is poked under the bonnet. No led required unless you are deaf in which case you will be able to feel the vibration/air flow.

 

[ernibv]

OK. This is where the problem begins No, I am not deaf, and I do have a pretty good idea how this generation of cars work. No offense taken
I have installed a new thermostat and sensor. Now, as predicted, if I pull the thermostat connection loose, the fan cuts in.
In the city or on the highway I don't hear the fan cut in. I'm also getting a max of 56 C at the the radiator hose.
A bad water pump would be causing other serious problems. Could just be an air-block ?
But that's the reason for a LED right at the fan connection. It could also be that the fan relay only reacts to a serious CPU malfunction alert, and other subtle signals don't trip the switch.
As an aside: disconnecting the thermostat will produce an Check Engine light. When the thermostat is reconnected, the Check Engine light remains .
Disconnect the ground from the battery, count to 10 and reconnect. No Engine Check light.

 

[s130]

Sorry but you have lost me. Forget all the electrical stuff and go back to first principles. Hands on Hoses

When the engine starts from cold at idle the top and bottom radiator hoses will feel similar in temperature. As things warm up one rad hose (normally top) will warm up but the bottom will remain cool. When the water thermostat opens the bottom/cooler hose will get very hot rapidly thus indicating/proving that the thermostat has opened and is functioning. If both hoses heat up together then the thermostat is duff and stuck open.

Am I missing something?

 

[Noideadave]

OK. This is where the problem begins No, I am not deaf, and I do have a pretty good idea how this generation of cars work. No offense taken
I have installed a new thermostat and sensor. Now, as predicted, if I pull the thermostat connection loose, the fan cuts in.
In the city or on the highway I don't hear the fan cut in. I'm also getting a max of 56 C at the the radiator hose.
A bad water pump would be causing other serious problems. Could just be an air-block ?
But that's the reason for a LED right at the fan connection. It could also be that the fan relay only reacts to a serious CPU malfunction alert, and other subtle signals don't trip the switch.
As an aside: disconnecting the thermostat will produce an Check Engine light. When the thermostat is reconnected, the Check Engine light remains .
Disconnect the ground from the battery, count to 10 and reconnect. No Engine Check light.

Sounds like you’re worrying instead of enjoying your B!!