K click relay mod to bypass MFRU

[Dave J]

Hi

Does anyone have a link or doc that provides detail on the relay mod to bypass the MFRU please ?

thanks 

[Jonathan Kay]

I suggest starting with Andrew Revill's article in Low Flying:

K-Click (amended following subsequent post)

Jonathan

PS: How far have you got in tracking down the cause of the problem?

PPS: You've posted this three times. You can't delete the others but you can change their Subject and the content so that all the responses come in this thread.

 

[Dave J]

sadly link doesn't want to work 

[Jonathan Kay]

Sorry, how about this?

Jonathan

[revilla]

Since writing that I have to say I've rather changed my opinion. Having seen quite a few of these cases I now think that the theories about high resistance in the "weak" relays in the MFRU are nonsense. The MFRU just contains 4 perfectly good automotive relays in a box. In nine if the vmcases that I've looked at have I actually found a oribkem with the starter relay inside the MFRU.

What makes all if the various "relay mods" work (and they usually do) is the fact that they usually involve a short length of stout new wire from the battery to the relay and from the relay to the solenoid.

The voltage drops responsible for K Click are usually along the wiring loom, through fuse box etc. It's removing these from the circuit and replacing with a good short wire that makes the difference.

I'm out today but drop me a PM if you want me to supply details of how I would bypass things now.

Andrew

[Geoff Brown]

The other major cause of the click is the fact that the primaries are so close to the starter that heat degradation of the solenoid &/or starter is to me the primary cause of the  problem. 

Having had this problem occur on two successive K series cars all I did was change out the starter for a more (allegedly) heat tolerant starter from Brise & fit an 18g ali heat shield over the whole unit. No hot wire relay mod or similar carried out.

Second K series car ran for six years & 22,000 miles without a hitch - then sold the car & it kept on going according to the new owner.

Original starters lasted 4 years/18,000 miles & 5 years/20,000 miles respectively.

 

[revilla]

Yes heat into the solenoid and an already rather marginal performance from the starter at the best of times are a major factor; everything adds up when you have that and wiring issues to contend with, plus sometimes mechanical friction from a solenoid mechanism that could do with a good clean! One comment I would make though; Geoff yours may have been fine but there have been a lot of cases where the Brise starter has caused ECU reset issues though inrush current transients. You end up with a car that needs throttle to start and for a while after starting before it will idle. It's a problem that has been acknowledged by the manufacturer, but I don't think there's a working solution. I would advise a WOSP or Powerlite as an alternative.

[Geoff Brown]

revilla #7 - both my Brise starters were of early vintage the last fitted 2005 so maybe the transient current problem is a new(er) occurrence caused by a change in how the solenoid & starter interact with the rest of the car electrics & more sensitivity of later ECUs ?

[Dixa1225]

My old car was a 1999 model year. Had exactly the same problem that Andrew described. I refub the old starter in the end.  

[anthonym]

Having been touring an an R500-K and its massive heat generation I have suffered I think all of the K Click problems; there are several and as far as I can recall them in no particular order except the first these are:

The thin wire to the solenoid i degraded by heat that reduces the voltage below 7v (iirc) which is insufficient to drive the solenoid. A give away is the wire being stiff when flexed between thumb and forefinger. (The thin wire to the alternator can do the same depending where routed, black I think.)

Same again with the thick wire. Mine snapped when flexed (off the car).

Starter brushes degraded by heat: mine disintegrated when touched.

that's all I can remember, I did write it up at the time at great length but it's now lost somewhere in the old posts. 

Several hours later I have found my old write up in web form, I don't think it was the final one I thought was definitive, but it offers a journey through the click of death practically in real time at the time I suffered it on tour probably over 1,000 miles from home in 2006, where I was rescued by Andre.

http://The_Now_Ancient_Story.html

and 

http://Pedro.html

or loaded in a different way:

https://www.supersevenheaven.com/K-R500/StarterRefurb/

Probably best viewed with both links open as the first refers to many items in the second.

I like to think pictures speak a thousand words. 

edit: looks like some of the full size images are missing, but I think all the thumbnails are there. I'll look for the missing.

edit2 yes it is early in my own click of death journey. It became clear over time there are many causes and no single solution short of getting a slower car (less heat generated, in some cases like an SV massively less.)

As regards the MFRU I dismantled one and was amazed how hard that was to do, far more robust than normal individual relays and won't fill with water in any circumstances. Having replaced one I was convinced had failed and then given the old one away for the new owner to use it with no problems in his car. 

Anthony 

[anthonym]

last time I spoke with Tim Brise, which was ages ago, he was saying he can't fix the problem without being sent devices that exhibit the problem. 

If it ain't broke he can't fix it - so I sympathise.

There was more to the conversation about competitors.. mentioned here in #20 as it happens.

Anthony

[Jonathan Kay]

"last time I spoke with Tim Brise, which was ages ago, he was saying he can't fix the problem without being sent devices that exhibit the problem. 

If it ain't broke he can't fix it - so I sympathise.

There was more to the conversation about competitors."

The fndings have been shared with Brise, and their proposed solution has been tested.

Jonathan

[anthonym]

sure, just not when I spoke with him, but pleased to hear it.

thanks for that link: more specifically here

#5 https://www.lotus7.club/comment/2359688#comment-2359688

[SLR No.77]

Re. Post #5

"What makes all if the various "relay mods" work (and they usually do) is the fact that they usually involve a short length of stout new wire from the battery to the relay and from the relay to the solenoid."

Nope. I had the "short cable relay mod" and yes it fixed it. However, when sorting out the badly bodged wiring in my car I decided that the extra relay located next to the battery was pretty crass and I'd rework the solution. Based on the theory that the loading caused by the Caterham starter motor is too high for the MFRU to be reliable, I reworked the recognised relay mod but did so by adding an addition relay to the relay stack above the passenger footwell, i.e. I now have 6 relays rather than the original 5, correct relay base sourced etc. 

I broke into the starter output from the MFRU (IIRC brown/red?) and linked the MFRU back through the loom to switch the new relay, probably around 1m in length. I've then taken the feed that already exists within the relay/fuse stack (2.5mm brown IIRC) to be switched by the new relay, then back through the loom to be reconnected where I broke into the original starter feed, again possibly another 1m of additional cable over the original setup, so the runs are now substantially longer than standard. I made this change around 10 years ago and it's been totally reliable. Locating the relay where it should be also meant I could add a blade type fuse at the same time, more o/e style than tagging it onto the battery.

Even though my car suffered from K-click, my mod still has the MFRU in circuit and has been 100% reliable, although with a second really it doesn't really matter whether the feed to the new relay is pre or post MFRU. I did suspect the MFRU relay would eventually fail completely but it hasn't, its working perfectly with the reduced load.

Stu.

[revilla]

Hi Stu, I'm sure the wiring you added and the various joints were of a much higher quality that some of the joints and splices I've found in Caterham and Rover looms! Did you ever find any direct evidence of the MFRU being faulty, other than the fact that the issue went away when you made the changes? I've measured voltage drops across the relays on a couple of cars that were actually experiencing the K-Click at the time and there was nothing significant, suggesting that at least on those cars the relays in the MFRU had nothing to do with it. I also replaced the MFRU on one of them with one that worked fine on my car and it made no difference; I then stripped the MFRU down for inspection and found no evidence of any issues. The relays look like fairly sturdily constructed automotive relays which should be able to handle the solenoid current, which is think is about 20A continuous and 30A transiently. I think the whole system is so marginal that additional resistance anywhere can lead to problems, so the causes in different cases are probably often quite different.

[SLR No.77]

Hi Andrew, my fault was the standard click issue, same as on my previous K-Series Caterham, I've not taken any measurements though.

My car had been badly messed with so during 2010/11, following a blown engine I reconstructed the Rover engine loom to return the car to standard, thereby agreeing with the wiring diagram for my age of car (1999). Any modifications I then "added" into the loom rather than making changes to the loom itself.

In this case I have simply cut into the feed (brown/red?) from the MFRU to the starter motor and added 6mm male/female spade connectors, the loom can therefore be returned to original by simply re-making this connection. With my relay modification in place it is effectively a new sub-loom that connects into the loom at this point, all the existing wiring is therefore still in place, but with the current diverted via the new sub-loom to include the additional relay.

The starter motor connections are original Caterham, as are the connections at the MFRU, the addition now being a couple of meters of additional cable making up the additional sub-loom, connected into the car loom at a point that was originally a continuous cable length.

Hope this helps!

Stu.