NMEA

It is usually a combination of poor install and poor fuel, few DIY installers even think about setting them up right let alone have an exhaust gas analyzer to set the burn rate correctly after they have installed or they have been fiddling. Poor fuel, high sulphur content meant that the lack of correct burn rate was compounded. That should be less of an issue now as apart from coastal marinas all red should now be ULSD. The ones that we have least trouble with are pro installed and regularly serviced so it speaks for itself. All that said, running at low burn rate makes things even worse if the above applies. I just wish they were all pressure jet instead of evaperator burners, we rarely have issues with the larger pressure jet models

No,why would my controling body for electronics and electrics care? but it is my position as a factory trained and appointed Webasto and Mikuni dealer and service tech.

If you are having to do a strip out service why on earth would you want to keep the fluid, do the job right and change it, the inhibitor in the Antifreeze is spent if it’s more than eighteen months to two years old.

Which Webasto do you have? if it is installed correclty then most will not fire up (or run at a reduced setting) depending on the temperature of circulated heating fluid it senses.

Unless I am replacing just a faulty gauge and need to match the original I buy most of mine from Fernaux Ridall wholesale but they are happy to supply retail at decent prices, they sell VDO in two styles, Wema and their own value line which are Durite and really quite good. Instruments They should match your current senders unless somebody has at some time used American senders which have a different resistance.

Good advice so far, highly indicative if not proof positive of a return fault, check the resistances of return(s) from the panel, particularly the misbehaving loads and the return conductor cable from the panel where it terminates at the battery or distribution point. Bright and tight connections are a good place to start, if no obvious faults or excessive resistance found there then inspect the conductors at any terminations in the circuit for blackening of the copper conductor.

Will do, but bear in mind that the MX60 CO2 adjustment (if needed) is acheaved by using shims in the combustion air fan and not one of the simplest procedures. "The member "Biggles" can not recieve any new email messages"

Perfectly adequate providing the 15m is a round trip from the battery and not a distance from it as a 10% voltage drop is acceptable for non mission critical stuff like domestic pumps, if it were something more critical like electronics then I would use 10mm2 and a distribution box closer to the load for the acceptable 3% drop. Don't forget undersised cables also waste energy, something you guys are quite mindful of I imagine. It's also about the quality of the termination, it's not a lot of use for instance using appropriate cables and then having terminations with cheap connectors that are not made properly and then corrode over time and introduce resistance to the circuit. For that reason I not only use fully tinned cable in every install or repair I do but only use tinned copper terminals with the correct crimp tool, people are often surprised to see that I have no less than seven different crimp tools for < 6mm2 terminals of varying types and that's not counting the hydraulic one I use on >6mm2 stuff. I'm not saying that is the only way to go but it gives the circuit the best chance of reliably performing over decades rather than years. Just high enough to see what's going on around me but not so high that I hurt myself if I fall off.

Of course there is, just as in any of the evaperator units, anything from a simple screw to hooking my computer and firing the ECU control software up, all require the use of a flue gas analyser that has been certifed and calibrated, it's definately not a matter of leaning it off, it may be within spec already, more a case of checking the CO2 in the exhaust and bringing it withinn the paramiters, that may mean richer even if it is running lean and burning out plugs and bosses, wicks etc, but most services I do result in reducing the CO2, or leaning it off as you put it, reduces the chances of coking rather than eliminates it.

I thought we were talking about water pumps here, not windscreen washer pumps

Apart from a glow plug which is really a cheap service item on a Mikuni as it is such old tech, the glow plug boss is usually worth replacing in my experience as it is difficult if not impossible to be sure you have got it completely clean,sometimes needs the mini slide hammer to get it out too. You may need to replace both side wicks but they are cheap enough. All the other bits are easy to clean and quite robust. The Mikuni, being the most agricultural and simple of the three main evaporator heaters is a simple thing to self service and though it can burn a bit rich and use more fuel and coke up if the exhaust CO2 is not adjusted correctly, but that really goes for all three. At least all you need to do it on the Mikunis is a flue gas analyser with light oil capability.

As a qualified (to NMEA 0400, BSI & ABYC standard) and certified marine electrical and electronics tech I object to that statement, the reliability of and electrical circuit can only be enhanced by using appropriately sized cables, the OP has made no mention of the pump draw so we’re all stabbing in the dark a bit but what I posted is not nonsense and I feel professionally insulted by the remark. Perhaps it’s working on seagoing vessels that tends to make me a little more finicky when it comes to installs. Reducing the stranding on a cable makes no sense at all but for the 6mm2 cable there are ¼” (6.3mm) spade terminals available to suit, and they are the correct un-insulated tinned type with a separate insulator applied after crimping not those Mickey Mouse Yellow, red, bleue car things that I see (and strip out) so often on boats.

Use a relay with ring terminal connectors which are easily available to take 10m2 conductor and run smaller cables to a small switch, one can often save money on large cable cost and / or mount the switch in a far more convenient place using this method as the heavy cable can usually be shorter and a more direct run.

As a Mikuni & Webasto appointed dealer I'm sorry to say that manuals for most of the Mikuni stuff are half in Japanese and a bit thin when compared to the Webasto and Eberspacher ones, that's if you can find one online,the ones for the MY30 and MY16 are OK but the smaller (non pressure jet) water heaters are not really much use. What makes you think you need a decoke?