Heater only working at maximum

[Jarvie.I]

Seems like it would be better to make a replacement using much higher rated resistors, these are clearly not up to the job and burn out.

I measured the resistors across from pointed end of fuse to pin3,2, and 1= Good resistor readings.
Measuring across the thermal fuse is open circuit. Will try a new fuse from ebay for about £2. I believe its a 192 degree unit at 15amp.
Original VW part £80, 2nd hand ebay about £45. £2 fuse gotta be worth a try.
Will try soldering after buffing away rust/ impurities- hopefully the solder wont melt when its on highest power. Will post results once done.
hopefully help others here if it works.

 

[oldiebut goodie]

You must use a heat sink to protect the fuse if soldering, don't try it without. I use a pair of medical forceps clamped on for these fuses.

 

[Unclebob]

You're better off replacing the lot with a PWM controller, something like this:

DC 6-60V 30A Adjustable LED Digital Motor Speed Regulator PWM DC Motor Speed Controller Motor Speed Control Governer 12V 24V 36V - AliExpress 13

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

I made an initial attempt at this a while ago but overcomplicated things by putting the unit in the same place as the resistor pack goes to cool the heat sink which required me to take out the blower motor cover which is an absolute PITA to get out. A small CPU fan would have worked fine, as would cutting a hole in the blower motor cover, as long as you make sure it's airtight when you're done.

I'm going to swap it out soon™ for one powered by a microcontroller (yes, I overcomplicated the installation and now I'm making it even more complicated). I can take some photos and do a little write up then, but the gist is that you replace the potentiometer with a small resistor pack hooked up to the same wires that go to the existing resistor pack and fan motor

It's significantly more energy efficient on low settings (I did this primarily so I could leave the blower sucking in fresh air in summer, running from my aux battery) but the real beauty is that you don't need to get the old resistor pack out, and I'm sure everyone that has tried to get those screws out will agree that's worth it!

 

[Jarvie.I]

I measured the resistors across from pointed end of fuse to pin3,2, and 1= Good resistor readings.
Measuring across the thermal fuse is open circuit. Will try a new fuse from ebay for about £2. I believe its a 192 degree unit at 15amp.
Original VW part £80, 2nd hand ebay about £45. £2 fuse gotta be worth a try.
Will try soldering after buffing away rust/ impurities- hopefully the solder wont melt when its on highest power. Will post results once done.
hopefully help others here if it works.

ok guys, got the thermal fuse from interner for a couple quid. fitted and working fine. As suggested i used pliers as a heatsink so the fuse didnt melt while soldering. So snipped off old fuse, gently filed to fresh copper on both studs, tinned the studs, tinned the new fuse- holding with pliers- soldered fuse in place again holding with pliers. Tested the fuse each time i used heat on it. Jobs done and working fine. I measured each resistor= all good. hopefully all pics will load showing my sequence. Again hoping to help others save a buck or 2.

 

[Jarvie.I]

ok guys, got the thermal fuse from interner for a couple quid. fitted and working fine. As suggested i used pliers as a heatsink so the fuse didnt melt while soldering. So snipped off old fuse, gently filed to fresh copper on both studs, tinned the studs, tinned the new fuse- holding with pliers- soldered fuse in place again holding with pliers. Tested the fuse each time i used heat on it. Jobs done and working fine. I measured each resistor= all good. hopefully all pics will load showing my sequence. Again hoping to help others save a buck or 2.

 

[Jarvie.I]

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I had long leads on fuse so i could grip it with pliers. After soldering in place i gently bent the leads back on themselves to sit in position shown.