Cushty mushty

Now as predicted, whilst in the shed (trying to re-assembled the lawnmower carb/engine/deck 'cos the grass is too long and I've already had it noted by the letting agents (would help if the landlord supplied something to cut the stuff with rather than me. And I have two, but they both are in bits, but that's bye-the-bye ) I have found the remaining bits of the third one that I was going to send with the first two. Grrrrrrrrr!!!! First two should land tomorrow I expect.

Fantastic stuff

Parcel rec'd from Clane via Belfast this morning - two more dead coil-y things.

Thanks Rich, and thanks Mark for doing duty as a post office again.
Rebuilt and ready for test (which I shall do tomorrow) and return to the land of peat and bogs.

Mac.

Wow, great to see a solution for this recurring problem!!! Good job Mac! I'm sure I have faulty units in my stock

Hi all.
Only too glad to help in this matter.
Cheers Mark.

UPDATE

The first "guinea pig" test pack indicates that I have not yet found a good solution!

When fitted to a real car the cut out operates after 10 secs on full speed suggesting that the "real" environment is rather hotter than my bench rig. I suspect that the foam filter and heater matrix reduce air flow enough to allow pack temp. to rise higher than the cutout spec that I have selected.

Or, of course the guinea pig motor may draw rather more current than mine. In any event a pack that has run perfectly on my rig has failed to do duty in the real world - I shall play some more! The need to thoroughly test is proved yet again.

Mac.

Suppose we need an Indian summer and a black bonnet with a hot engine to see what it behaves like under extreme conditions.

Get Logan to test one?

What we could do with is for someone to get a cheap thermometer and place it in the airbox to see what the temps actually get to.

Already being done with an "expensive" thermocouple!

Mac.

That's what I like to see - a massively expensive and over complicated solution to a simple problem......

I'm really glad to learn it's such a simple problem.

In my obvious ignorance I have found the thermal cutout responds to the temperature of the bi-metallic frame (obviously) but this temperature is VERY different to the environment in which the pack sits (even a distance of 3-4 mm from the cutout contacts gives a temp drop of 15c).
I bow to your superior knowledge and await, please, your advice where you would place your simple thermometer and how you would read it (to truly reflect the situation it would need to be sealed in the heater box - not the easiest to open).

Again my naiveity has tripped me up with my assumption that it is not enough to measure the environment around the resistor, but it is the temperature reached in the bi- metallic switch (generated by current draw as well as pack and air temp that must be ascertained.)

Perhaps I should recognise my limitations and give up my pottering - allowing a more capable researcher to use a less complicated solution to arrive at a suitable thermal protection.!

I remain, too complicated for my own good - Mac.

Would you like some assistance in climbing off that rather tall equine being you appear to on?

By 'the simple problem' I meant ascertaining the temps reached in where the resistor pack sits, and using a cheapo thermometer (or even an outside temp gauge set-up) would be the cheap and cheerful way of doing this.

However, as you say, this is only part of the overall problem which is somewhat more complex than just pure temperature.

Presumably airflow is somewhat less than anticipated resulting is a lower cooling effect than previously thought. Not having a 300 to hand I can't check, but is the air intake for the airbox sealed against the bonnet, and if so how effective is the seal particularly given the cars are now a minimum of 22 years old? Could hot underbonnet air be drawn into the airbox raising the temperatures above what we expected? As the intake is at the bottom of the windscreen does this mean that it is in a low pressure area so the amount of air being ingested is less than previously thought? Is the current draw in 22+ year old wiring higher than previously thought?

Thank you for the offer - but having had years of practice falling off gates backwards for tourists, falling off a simple horse won't be a problem.

One comment - on the guinea pig car the cutout operated after 10 secs on full speed (this having just fitted the unit on a cold car). Bearing in mind the time involved it is unlikely that under bonnet temperature is a factor here. The annoying thing is that the pack performed flawlessly on the bench (in an assembled heater box but with no matrix). Plainly there is something "simple" I am missing.

Havn't completed the point to point yet - will fall off later.

M..............................ac.

V6 Man wrote:Is the current draw in 22+ year old wiring higher than previously thought?

Resistance will be higher, therefore total current in the loop lower if anything :s

Mac, mk2 vs mk3 heater box causing the issue maybe? The resistor is in a fairly different place in each.