I've used the resistors you have their Anjo to dump a lot of power, but they have got very very hot.

My thoughts are move to something more modern, the golf (mk2) pack I ran for a while has no exposed coils, not done loaded temp tests though. Worth seeing what a scrappy BMW mini has maybe (they are my current "modern car that people will support for years" hopeful)

The 940 resistor pack is a ceramic coated module, so may not need the cutout, or the 940 may have fire resistant plastic around it. We need to replicate the original fire safety mechanism or modify to not require it. We can't just use parts form other cars without knowing the full story.

Been playing around!

My test box made and working.





Results:-
Input V = 12.4

Speed 1. Momentary 6A runs @ 2A Full air flow pack @ 42c - no air flow peaks @ 110c
Speed 2. Momentary 10A runs @ 4A Full airflow pack @ 18c - no airflow peaks @ 92c
Speed 3. Momentary 15A runs @ 6A Full airflow pack @ 16c - no airflow peaks @ 18c

Going to play some more!

Mac.

Fantastic work Mac! Only a matter of time before you find a solution to this problem.

How did I miss this

Making decisions based on data, it'll never catch on

Fantastic work, watching with interest - especially as mine's broken

Ok chaps, I've now developed a technique to refurbish said resistors! I have had a couple of test units running on a rig for over 30mins on each speed with no problems. Blocking airflow or stalling motor causes the (new) thermal cutout to operate within 20secs. Restoring airflow allows almost instant automatic restart.

So far I have worked on the post 86 resistor pack that sits in "full" airflow, I have not yet looked at the earlier type that sits "upstream" of the fan in less airflow.

I would now like some guinea pigs (yes Steve - you?) with failed units who would be prepared to send them to me, (I will refurbish and return), and then "on car" test it in normal use.

Also I would like samples of the earlier (3 connection) unit to "play with".



If all works out as I hope I should be able to offer some sort of refurbishment or exchange scheme BUT I have to be sure we have a viable "long term" solution - and this means testing in the "real world" not just on a rig.

Mac.

I have one or two "dead" ones saved here Mac, I could put them in the high speed getting things done pile (so it'll only take a couple of months?)

I've packed some already.

Looks great!! Happily be a guinea pig - I'll reply to your PM

Need the motor voltage(s) please if you still have it setup, and don't forget supply is more like 14V with engine running. Although relatively calculatable, I suppose I should work it out.

At 12.4v it should be about 8.8V and 4.4V, which would equate to about 4x6A and 6x3A diode (P600 in maplin eg, about 0.85-0.9V drop @4A), however they would still dissipate the same power as resistors just perhaps over a wider area.

A PWM controller would be more efficient but also more expensive and might whine, the replacement cut out is the most sensible.

As requested -

3 packs now fettled

Input voltage 12.4
Pack 1 voltages at motor are 6.3, 9.5, 12.2.
Pack 2 voltages at motor are 6.5, 9.6, 11.8.
Pack 3. voltages at motor are 6.3, 9.6, 11.8.

Mac.

I guess the motor is not like a resistive load atall lol.

Update

First customer "test" unit rec'd.

As received - with totally ff'd cut out.





Unit dismantled and Macs secret weapon employed,



The resistive coils nestling in the cleaning bath after the first session,



The rebuilt unit,



Fitted to the test rig,



And running at full speed!



Unit now posted back to guinea pig who will report in due course.

I will keep the forum advised.

Mac.