BXProject

[mat_the_cat]

Yes. All you are doing by bridging the terminals is replicating the action of the switch. It's possible that the terminals are not making proper contact with the switch (but are with whatever you bridge it with), so you could try squashing them a little to grip it better, as well as cleaning if they look corroded. He'll not need a cooling fan up there anyway though so don't worry about it!

[Philhod]

Basically Mat that's just what I did to mine and it's fine.

You said it's working on full. That's ok because it's prompted by the heat sensor on the side.
If it only runs on fast it will cool quicker and switch off again earlier. It's the fact that it is switching on and off at all that really matters. My Meteor only ever came on full and it worked fine like that for years.

[Way2go]

There is no heat sensor on the side Phil. The switch itself contains bi-metal thermal contacts that perform this task.

If the switch works in fast but not in slow then the slow contact is fucked and the fast one is likely close to failing so the switch needs replacing. The only other cause for this on slow is the resistor or integrity of the connection but which have been checked as ok by the bridging test.

The slow speed occurs first so without it the system raises to a higher temperature before the high speed cuts in causing unneccesary stress on engine components. This will occur at the worst times ie in traffic jams or slow moving traffic as when the car is moving at speed the fans will not normally be called upon.

[mat_the_cat]

The other benefit to the slow speed coming on first is longer contact life. I'm not sure whether this as part of the reason for the design or just by chance though. By switching the fan on via the resistor, the switch contacts pass a low current to start with and then a second set of contacts close to power the fan directly, but as current is already flowing the current switched at each stage (and hence arcing) is less.

[Philhod]

No there wasn't on my Meteor but K39 has one and it connects to the warning and temp guage too.


If the contacts are goodand have a little vaseline on them there should be no arcing Mat.
In any event My Meteor had the fault when I got it and it was still working fine when I sold it.
I couldn't be arsed fixing something of negligible importance.

[mat_the_cat]

If the contacts are goodand have a little vaseline on them there should be no arcing Mat.

No no no! I meant the switch internal contacts!


An ideal switch moves the contacts apart as quickly as possible (especially in high current DC applications) to minimise any arcing. With the thermal switch (presumably) using a pair of bimetallic strips the action may be slower than ideal hence anything to minimise arcing is a good thing.

[Philhod]

I should put that stick down, if I were you. Before I have to take it from you

[mnde]

OK, so am I right that bridging the contacts with the plug in situ will test the connectors as well? There was LHM all over the place from where the "little octopus" split. I sprayed plenty of WD-40 into the terminals but maybe that wasn't good enough. I'll try squeezing the terminals to get them to grip better and cleaning them with contact cleaner. I think from memory, with the plug in situ, the low speed contact is the uppermost one.

I was wondering about the stress on the switch caused by going straight to full speed... but with the downturn in temperature the fan never came on in the last few days.. (never got stuck in traffic, most of my journey to/from work is on the A3) and it's resting at home now.

I just want to see if I can get it working again for the chap's journey to Scotland in mid October, in case of big traffic jams or steep ascents.

Mark.

[mat_the_cat]

OK, so am I right that bridging the contacts with the plug in situ will test the connectors as well?

Yes, if you can get to the connectors on the switch without pulling the terminal block off.

[mnde]

Yeah, I thought a long thin (plastic handle!) screwdriver or knife would do the trick, bridging the connectors.

Mark.

[Philhod]

I used a folded, stiff piece of emery to push into the contacts on the rad end to clean them first, blew out the dust, squeezed them together a bit then smeared some vaseline on and all was ok. Never took the switch it'self apart though.

[mnde]

I used a folded, stiff piece of emery to push into the contacts on the rad end to clean them first, blew out the dust, squeezed them together a bit then smeared some vaseline on and all was ok...

"Ooh you are awful. But I like you!"

[mat_the_cat]

[Way2go]

No there wasn't on my Meteor but K39 has one and it connects to the warning and temp guage too.

The sensors for the temp warning lights and gauge do not operate the rad fans, that is the task of the switch at the bottom of the rad with the 3 contacts.

This switch is on all models but there are some wiring variations though. In the case of 2 rad fans the fans operate in series for slow speed and parallel for fast speed. The air-con also is fitted with relays that override the fan switch for continuous operation when air-con is engaged.

So even with 2 fans Mat's explanation holds true in that the current through the slow contact is halved and when the fast contact is engaged it will no longer see the very high start-up current that could quickly burn it out.

[Philhod]

Well I've not much idea electrickerly wise and the only leckies I've ever come across come out with scenario's that although technically may be true, in actual fact rarely happen, unless there are other problems.

There is one wire on K39, that runs from the connection on the side of the rad to the one at the btm. So I just assumed it had something to do with it.

All I can say is the Meteor only worked on full for ages without any ill effects.

[mnde]

OK, so am I right that bridging the contacts with the plug in situ will test the connectors as well?

Yes, if you can get to the connectors on the switch without pulling the terminal block off.

OK - so I bridged the ground and upper contacts with the plug withdrawn slightly to reveal the contacts. The low speed works fine.... so it's got to be the switch. I even tried opening the rad bleed screw after a run, in case I had an airlock, but no. The fan still twitches instead of coming on at low speed.... then comes on at high speed.

I'm loathe to buy a spanner just to do this job... (the largest one I've got is 23 mm) so what are the chances of getting the switch undone with an adjustable spanner?


Cheers,

Mark.

[docchevron132]

I've always used adjustable spanners for rad switches, never failed yet!
That said, i do have some fucking epic stilsons, just in case!

[Philhod]

I have one that grabs spheres like they were golf balls. Unfortunately it;s that big I can only use it when the car is on a lift as the handla is over 4ft long.

[docchevron132]

I have similar stilsons! For spheres, I use the proper tool..