TM-4 alarm and Fan relay

[Gefail]

Sorry for the drawing....the two cables out of the TM4 go to the coil of the 12v relay. Then you need to bare the two wires that go to the plug of the temp sensor near the handbrake. Connect (4 pin relay) one contact to one of the now bared temp cable and connect the other contact to your 390 ohm resistor (Maplin think I used a 1/2 watt)
The other end of the resistor connects to the other bared temp cable. I soldered & nsulation taped the joints.
To test just set relay point down to displaye engine temp.
Just a case of setting alarm poit's to a degree or two above normal operating temps. Every Bongo seems slightly different. Hope all that makes sense, any problems just yell.

[vitus992]

Thank you
It looks like you have the relay in place of where I have a physical switch.
I really appreciate your time

Daren

[Gefail]

Yes same place...seemed easiest option. When I installed it couldn't get it to work at first, found the relay was a dud.
Happy tinkering.

[vitus992]

Once again, many thanks.

[cmm303]

if you are still considering driving the rad fans ....

The wiring diag for the fans will help http://www.g8dhe.net/bwm/bwmanualp.htm?1995/Page_50
When reading this diag, it helps to remember that the fans are driven at normal or high speed by the ECU based on engine temp, and they are also driven for air con.

No direct experience of what you want to do but I would not interfere with the control circuits driven by the ECU but connect an additional relay with its contacts in parallel to the existing fans-on-normal-speed relay. This additional relay is controlled by your TM-4, directly or indirectly depending on ratings.
You may need to do some investigation to identify the relay in question. To help with this, you can force the ECU to drive the fans in the various modes by inserting a resistor in the end of temp sensor lead. Don't need engine running just ignition on. (100 ohm = high speed; 160 ohm = normal speed; 330 ohm = off. assuming the trigger points are the same as my Bongo!)

I suppose an alternative approach would be similar to the scavenger fan, switching in a low value resistor into the feed from the engine temp sensor. Personally though, that feed is so important I would prefer not to meddle with it.

[g8dhe]

Please don't put them in parallel with the existing relays, the ECU might decide to operate the other relay at the same time!

[mikeonb4c]

Please don't put them in parallel with the existing relays, the ECU might decide to operate the other relay at the same time!

Geoff - what would be the effect of taking a fresh feed direct from the battery to the fans (using a relay switch given currents involved). Would that work?

[g8dhe]

Its not the feed as such, you need to isolate the ECU trying to operate the fans at the same time! If you power up the slow speed and the ECU turns on the high speed then I am not sure what will happen but some dual wound dual, dual commutator motors won't like it. Others won't care a hoot, but I don't have a diesel to try it out on ....

[vitus992]

Cheers Geoff, the oily bits I can just about get my head around but the electrics are a dark art to me so unless I can find a guide on how to do it I shall not go near.

[cmm303]

Please don't put them in parallel with the existing relays, the ECU might decide to operate the other relay at the same time!

ah yes, I understand where you are coming from. Apologies to the OP.
I can't check the diagram right now but I thought it was safe because, if I recall correctly, one relay switched a 12v feed and the other switched to earth. I assumed the later changed the speed. Guess the assumption has made an ass of me!

[g8dhe]

There are three relays B6-01,-02 & -03.
B6-01 & B6-02 apply power to one side of the commutators, B6-03 applies an earth to the second commutator,
which control which speed I don't know having neither a vehicle or a diesel manual!
I do know that not all dual wound motors are designed to have both powered at the same time, I have personally witnessed the result and loss of magic smoke! But they can be designed to work quite happily.
Volunteers and donor vehicles please to apply power to both and find out ?

[mikeonb4c]

There are three relays B6-01,-02 & -03.
B6-01 & B6-02 apply power to one side of the commutators, B6-03 applies an earth to the second commutator,
which control which speed I don't know having neither a vehicle or a diesel manual!
I do know that not all dual wound motors are designed to have both powered at the same time, I have personally witnessed the result and loss of magic smoke! But they can be designed to work quite happily.
Volunteers and donor vehicles please to apply power to both and find out ?

I have used a direct feed to the scavenger fan without ill effect for 9 years or so (the sensor/resistor trick hadn't been unearthed at that time). HOWEVER, i imagine that is a much simpler circuit than the rad fan set up. But it is why i asked. Sounds to me like the rad fans are best left well alone unless there is a ready way of taking the ecu controlled relays out of circuit when the over-ride is switched on?

[vitus992]

Thank you mike, I have to agree, I am not electrically minded enough to crack this one on my own. I shall remove my scav fan manual switch and prog the TM-4 to cover it.

[teenmal]

There are three relays B6-01,-02 & -03.
B6-01 & B6-02 apply power to one side of the commutators, B6-03 applies an earth to the second commutator,
which control which speed I don't know having neither a vehicle or a diesel manual!
I do know that not all dual wound motors are designed to have both powered at the same time, I have personally witnessed the result and loss of magic smoke! But they can be designed to work quite happily.
Volunteers and donor vehicles please to apply power to both and find out ?

or I have used a direct feed to the scavenger fan without ill effect for 9 years so (the sensor/resistor trick hadn't been unearthed at that time). HOWEVER, i imagine that is a much simpler circuit than the rad fan set up. But it is why i asked. Sounds to me like the rad fans are best left well alone unless there is a ready way of taking the ecu controlled relays out of circuit when the over-ride is switched on?

That is probably because the ECU very rarely calls the SF and when you have switch on the fan the ECU was sleeping, its a different kettle of fish with the ECU and the cooling fans.

[mikeonb4c]

Yup totally get that Geoff. You da man.