Transmitter lead connection ?

[mrdoiron]

I have a transmitter lead NOT connected to anything... so that doesnt sound all that right... my guess is it is a coolant temp transmitter lead - not sure - but don't know where to connect it to, likely makes it's way back to the dash gauge ? (assuming that even works not really sure) . Can anyone help guide - any pictures on where it is supposed to connect to would be greatly appreciated....

thanks, mike

[jac04]

That is the cold start warning light temperature switch. It causes the cold start light on the dash to come on if the choke knob is pulled out and the coolant reaches a certain temperature - basically telling you to shut off the choke. My 63 had this set-up, but I'm not sure when it was phased out.

Newer models do not use that sender. The choke light on the dash simply comes on when the choke knob is pulled out.

[mrdoiron]

That is the cold start warning light temperature switch. It causes the cold start light on the dash to come on if the choke knob is pulled out and the coolant reaches a certain temperature - basically telling you to shut off the choke. My 63 had this set-up, but I'm not sure when it was phased out.

Newer models do not use that sender. The choke light on the dash simply comes on when the choke knob is pulled out.

Thx Jeff,
is it possibly that connects directly somehow ? The cold start light does come on when I pull out the choke, yet there is not wire connected to this lead ?

mike

[bkreutz]

If you look at your choke cable, you'll find a switch attached to the cable, that's what activates the light. So it's not really a "cold start" light, but more properly a "choke on" light. Don't have any experience on how they incorporated the temp sensor into that system but would imagine it would make a light come on when the engine temp was below a certain temp and then go off as it came up to temp. Too "Rube Goldberg" in my opinion. :D

[mrdoiron]

If you look at your choke cable, you'll find a switch attached to the cable, that's what activates the light. So it's not really a "cold start" light, but more properly a "choke on" light. Don't have any experience on how they incorporated the temp sensor into that system but would imagine it would make a light come on when the engine temp was below a certain temp and then go off as it came up to temp. Too "Rube Goldberg" in my opinion. :D

I understand, thx... just the light is labeled "cold start" on the dash is why I referenced that.

so the light "could" just indicate it being pulled out, however the choke definitely is work when pulled out, so not just activating the light.

Anyone have anything that references where the lead in the picture is supposed to connect to ??

thanks again
mike

[jac04]

... but would imagine it would make a light come on when the engine temp was below a certain temp and then go off as it came up to temp.
No. Like I stated in my first post, the switch would make the light come on when the engine gets up to a certain temp, to let you know to shut off the choke.

Mike-
Since your choke light comes on when you pull out the choke, you most likely don't have a system that uses the cold start switch in the head. You could incorporate it into your system if you want, by having the ground for the cold start light go through the switch (IIRC, the switch just makes a contact to the head when it gets to a certain temp, completing the circuit.

[mrdoiron]

No. Like I stated in my first post, the switch would make the light come on when the engine gets up to a certain temp, to let you know to shut off the choke.

Mike-
Since your choke light comes on when you pull out the choke, you most likely don't have a system that uses the cold start switch in the head. You could incorporate it into your system if you want, by having the ground for the cold start light go through the switch (IIRC, the switch just makes a contact to the head when it gets to a certain temp, completing the circuit.

Ok, I had a guy work on the truck when I got it, and I recall he said he also got the "choke and light working", and didn't think much about it, as I really never need the choke at all. I wonder if he did something to wire the choke / light differently than it was intended to... There wasn't anything connected to the lead in the picture even when I got the vehicle, and I'm not sure what it is supposed to connect to directly. Wiring not one of my spiritual gifts...

mike

[mrdoiron]

No. Like I stated in my first post, the switch would make the light come on when the engine gets up to a certain temp, to let you know to shut off the choke.

Mike-
Since your choke light comes on when you pull out the choke, you most likely don't have a system that uses the cold start switch in the head. You could incorporate it into your system if you want, by having the ground for the cold start light go through the switch (IIRC, the switch just makes a contact to the head when it gets to a certain temp, completing the circuit.

So I think I get how it is supposed to work: related to the negative ground; ... Whereas the oil pressure warning light works by having current going into it at all times, and grounds out when the sensor senses less than sufficient pressure - leading to the lamp being illuminated; the cold start lamp works sort of the opposite of the oil pressure warning light. When the engine is cold, the thermostat isn’t grounded, but when it heats up, the thermostat grounds out, causing current to run from the battery to the light, then through the switch on the bulkhead which is actuated by the choke cable, then to the ground on the thermostat...which lights the indicator.

I still am not sure what that terminal lead (in the pic) needs to directly wire-to however (today nothing)...direct to the back of the dash temp gauge ??

thx

[Terrys]

the cold start lamp works sort of the opposite of the oil pressure warning light. When the engine is cold, the thermostat isn’t grounded, but when it heats up, the thermostat grounds out, causing current to run from the battery to the light, then through the switch on the bulkhead which is actuated by the choke cable, then to the ground on the thermostat...which lights the indicator.

Pretty Much.

You should familiarize yourself with the schematic, it will save you endless questions:

http://www.roversnorth.com/store/images/category/medium/LR-page83.pdf

[TedW]

Newer models do not use that sender. The choke light on the dash simply comes on when the choke knob is pulled out.

FWIW, my 1970 has this.

[kevkon]

So does my 72

[jac04]

^^ Interesting. My 63 had it, but not my 69, 71, or SIII Lightweight.

[bobzinak]

all that thing does( the probe with the three bolts on your head) is ground out the lead connected to it. It was on my 71 2a. in fact the 2.5 heads have the hole that is not machined out. all it does is ground the choke wie completing the circiut for the choke light..it is a thermal switch that comes on when the coolent gets it warm enough. by diectly grounding the lead from the choke knob, the choke light will come on no matter what the engine temp is... it is just a reminder to push the choke in. my 2.5 motor didn't have the sensor on the head so I just grounded the wire so the choke light would come on whenever the choke was pulled out..it is basically just a temperature switch that completes the ground when the engine gets warm...not rocket science...12v goes to choke cable switch behind dash, through the bulb, to ground via the switch on the head..

[SafeAirOne]

Thx Jeff,
is it possibly that connects directly somehow ? The cold start light does come on when I pull out the choke, yet there is not wire connected to this lead ?

mike

Umm...I might be wrong, but I suspect that you may be misunderstanding how your original system was supposed to work. Forgive me if I'm the one that's misunderstanding whether or not you are misunderstanding but...

It should be wired so that 12 volts goes into one end of the switch that is mounted on the choke cable. When you pull the choke cable the switch closes, sending the electricity out the other end of the choke cable switch and down the line to the water temp switch, where the electricity will stop because that switch is open when the engine is cold. Once the engine warms up, the water temp switch will close, allowing the electricity to complete the path to ground. Once that path is complete, the electricity will flow, illuminating the cold start lamp.

The top part of the picture is the way it should be, the way I described above. Below that is what you have--Specifically, the temp switch is out of the circuit completely and the other side of the choke switch is wired to ground. This way, all you need to do is pull the choke out, closing the choke switch, completing the path to ground, illuminating your cold start lamp. Whew!!

http://farm2.static.flickr.com/1336/4726743072_589cb8ba33_b.jpg

[siii8873]

on the two rovers i've had the cold start light has two components, the switch on the choke cable and a temp sensor switch. It is as noted above a turn the choke off light. the temp sensor switch is located directly under your finger in the picture. if the choke is pulled and the temp comes up enough to close the temp sensor the light comes on.
I would think that this wire needs to be shorted for th loght to work as yours does.

[mrdoiron]

Umm...I might be wrong, but I suspect that you may be misunderstanding how your original system was supposed to work. Forgive me if I'm the one that's misunderstanding whether or not you are misunderstanding but...

It should be wired so that 12 volts goes into one end of the switch that is mounted on the choke cable. When you pull the choke cable the switch closes, sending the electricity out the other end of the choke cable switch and down the line to the water temp switch, where the electricity will stop because that switch is open when the engine is cold. Once the engine warms up, the water temp switch will close, allowing the electricity to complete the path to ground. Once that path is complete, the electricity will flow, illuminating the cold start lamp.

The top part of the picture is the way it should be, the way I described above. Below that is what you have--Specifically, the temp switch is out of the circuit completely and the other side of the choke switch is wired to ground. This way, all you need to do is pull the choke out, closing the choke switch, completing the path to ground, illuminating your cold start lamp. Whew!!

http://farm2.static.flickr.com/1336/4726743072_589cb8ba33_b.jpg

Agreed here... this is what I tried to explain as my understanding, this answer and the next are clearer however... so I need to connect to the water temp lead to the switch near the firewall behind the dash...however is there a fuse in-line prior (between 46 & 59 on your diagram) ? Today I assume the choke cable switch is just going to ground instead to the water temp switch as your bottom diagram shows - just need to make it back home to validate this on Friday...

thanks again, great help guys - mike

[109 Pretender]

My 67 109 has this 'do-hickey' as well. It's a wax bulb that is supposed to open the gnd connection to your choke lamp after the engine warms up enough to not need a choke to run. Light goes out and then you manually turn off choke. This is an early attempt at what I call H/W level 'plug and play'. You see, after our education system began failing - instead of trying to educate people on how to use the technology in their lives, engineers decided to design around our now faulty minds. Been going downhill in this direction ever since - hence the 'automatic choke'...

It appears your mech wired the lamp directly to gnd. And that's ok too. YOU just have to remember to turn off choke when engine starts chugging black smoke out and runs rough after it's warmed up.:D

IIRC that part is not cheap and they usually are bad.

Cheers!

[jac04]

It's a wax bulb that is supposed to open the gnd connection to your choke lamp after the engine warms up enough to not need a choke to run. Light goes out and then you manually turn off choke.
No. The water temp switch closes the connection to ground when the engine warms up. The light comes on, then you manually turn off the choke.
See SafeAirOne's post for the correct information.

[SafeAirOne]

No. The water temp switch closes the connection to ground when the engine warms up. The light comes on, then you manually turn off the choke.
See SafeAirOne's post for the correct information.


PLEASE NOTE: I didn't consider the possibility of the temp switch working the other way round when I made the diagram. I don't have a choke, let alone a water temp switch, so don't rely on my theory of operation of the temp switch to be factual. I will say with enormous certainty that the wiring diagram is correct, though.

I will admit that I hope my theory of operation is correct, because I can't go back and edit my lenghty response anymore... ;)

[jac04]

...I hope my theory of operation is correct...
It is.

[Sputnicker]

By the way, a lot of old British cars used this switch, which is commonly referred to as an "Otter" switch. Be sure you get the "normally open" version, which shorts ("closes") when hot.

[mrdoiron]

By the way, a lot of old British cars used this switch, which is commonly referred to as an "Otter" switch. Be sure you get the "normally open" version, which shorts ("closes") when hot.

So what is there today seems original ... so it should be correct and close/short when hot.

thanks gents, mike