Post EuroTour Modifications

[v8s4me]

I've bought these waterproof connectors to connect the fans to two independent circuits. The specs I have for the fan do not give am amperage rating ans there is nothing with the connectors to indicate what they can handle.The pins are 1.5mm across. Will they handle the load? Thanks in advance



The next mod will be to the drainage pipes to stop the boot flooding.

[RayTVR]

The connector for the 1.5mm cable is rated at 16A

From here

From memory the fans are on a 30A fuse, so maybe would need something a little beefier.

[v8s4me]

I've managed to find this which indicates a current input of 8.5A max. So if the 1.5mm connector is rated at 16A then hopefully I'm OK. But why would the fuse be 30A then?

NB. I have two of these fans.

[GreenV8S]

If you measure the resistance of your fan motor you can calculate the inrush current which will represent the peak load. You really want your connectors and wiring to be rated comfortably above this. Since it's a brushed fan the resistance will depend on the position of the fan so measure at several positions - but don't turn the fan while the meter is connected in resistance mode.

[v8s4me]

With the meter on the 2K scale I get readings of between .003Ώ to .009Ώ. So presumably this is 9Ώ max? Have I put the decimal point in the right place? So is it A=V/R ie 1.3A. Or is it 13A?

[RayTVR]

Not as easy as that I'm afraid. As a fan is an inductive load (a big coil) then technically its an impedance rather than a resistance, so inrush current will be a lot higher than state state running (hence the need for a high value fuse)

[greymrj]

Joe, there is a discussion on here http://forum.lro.com/viewtopic.php?f=21&t=4548... of wiring 2 fans on a Landrover, which is a very similar set up. Although the 1.5mm pin is theoretically marginal it should not be a problem, the 30amp fuse would go before the connector went. If anything I think the 30 amp rating is too high and I am pretty sure the relay is only rated at 20amp?. Incidentally I use exactly the same waterproof connector for the Kenlowe on her MGB GT and it doesnt show any signs of getting even the slightest bit warm.

[greymrj]

I take what Ray says about the fuse, it will be higher than the circuit would appear to require.

As far as the boot leak is concerned: There are two pipes leading down from the rear corners of the boot lid recess which are supposed to deal with the water. However these pipes are of a very basic quality and get kinked (often near the lights or where a jack has been dumped on them!)and blocked by debris. Mine were in a bad way and I replaced them with a slightly larger bore reinforced pipe sleeved on to the drains, and carefully contoured so it didnt kink or block. I still have to check them regularly (with a length of cycle cable inner) but then mine is parked outside under a tree all the time. I do have 2 drain holes with (stainless!) external covers but they haven't been needed (so far....and I also went through the biblical rain in Belgium)

[GreenV8S]

RayTVR said:

Not as easy as that I'm afraid. As a fan is an inductive load (a big coil) then technically its an impedance rather than a resistance, so inrush current will be a lot higher than state state running (hence the need for a high value fuse)

The inductive characteristics don't affect the peak current. The peak current will occur when the fan is stationary and acting as a simple resistor with a DC load applied. It can be calculated just from the supply voltage divided by the resistance in Ohms between the brushes. The resistance will vary depending on the orientation of the commutator so you need to measure in several positions to make sure you have caught the lowest value. Just be careful not to move the motor while the meter is connected in resistance mode or the motor acting as a generator can fry the meter.

[phillpot]

Inductive? Resistive? peak current? All getting very technical! A couple of bog standard bullet connectors have presumably done ok for the last 25 years?

Just pop one of these in, should do the trick


And a dollop of this

[magpies]

Water in the coilpack did it for me. So temp fix now is a sandwich box.

Edited by magpies on Saturday 4th June 20:08

[magpies]

[greymrj]

phillpot said:

Just pop one of these in, should do the trick

B..... h..., you could jump start the Titanic with that! Stick with the nice one you had, it will be fine, and a lot less hassle to fit.

[Buzzlt]

Hi Joe
Your meter will unlikely be accurate to less than 0.4 of an ohm so think you are wasting your time trying to measure it. If you really want to know get one of these

http://www.maplin.co.uk/p/400mm-automotive-current...

From experience (I used to replace a lot of air conditioning fans on vans) anything rated under 20A tends to melt after a while. If it was me I would just use straigh through crimps as long as there is a bit of spare wire In case you need to do it again. Oh and decent crimpers of course. You need a special tool for those other things as well.

Cheers Greg

[phillpot]

Buzzlt said:

Your meter will unlikely be accurate to less than 0.4 of an ohm so think you are wasting your time trying to measure it. If you really want to know get one of these ...............

Hi Greg, do think that little gizmo would have over current protection?

This is the standard "Orange housing" fan on my S3 (V8 the same?), needle banged up against the stop, 30+ amps, on start up

[v8s4me]

This might be an over simplistic way of looking at this but...



There is significantly more metal in the connector pins than there is in the "bridge" on a 25A fuse. So surely the pins can handle the start-up load?

Anyway, it all seems to be working and nothing has melted yet. There are now two independent fans. One connected via the otter switch and blowing air over the RH side of the rad (where the top hose goes in to rad), and the other on the LH side of the rad, controlled by a switch under the dash. Each has an independent live feed, earth, fuse and relay.

It's still damp inside but at least it's clean on the outside now.

[Top Gear TVR]

No mods here just maintenance:

[v8s4me]

Top Gear TVR said:

No mods here just maintenance:

Excellent! How are you getting with the rack?

[greymrj]

v8s4me said:

This might be an over simplistic way of looking at this but...



There is significantly more metal in the connector pins than there is in the "bridge" on a 25A fuse. So surely the pins can handle the start-up load?

Anyway, it all seems to be working and nothing has melted yet. There are now two independent fans. One connected via the otter switch and blowing air over the RH side of the rad (where the top hose goes in to rad), and the other on the LH side of the rad, controlled by a switch under the dash. Each has an independent live feed, earth, fuse and relay.

It's still damp inside but at least it's clean on the outside now.

Not simplistic, realistic, I totally agree with you.
One thing however; I never like crimped terminals of any type when there is damp around. Effectively there are three contacts (wire to sleeve, sleeve to sleeve and wire to sleeve) and three points to corrode. With a bit of care it is easy to solder the wires to this type of connector which gets rid of two potential resistances.

[GreenV8S]

v8s4me said:

This might be an over simplistic way of looking at this but...

I think the issue is not the cross section area of the metal of the terminal, but the contact area and clamping force of the connection between the terminals. There will always be some contact resistance, but if this is excessive (for the current) then it will cause heating which will gradually damage the contact surfaces.