Technical Heater Blower fuse

[Nickkdx]

Hi, 2001 Fiat based Hymer motorhome,in 2014 I had the heater blower fan fuse melt the fuse hold on the fuse board so I bypassed the fuse board and fitted separate fuse hold and now that has melted as well , any suggestions as what would cause it, could it be the blower resistor.

 

[Communicator]

Hi, 2001 Fiat based Hymer motorhome,in 2014 I had the heater blower fan fuse melt the fuse hold on the fuse board so I bypassed the fuse board and fitted separate fuse hold and now that has melted as well , any suggestions as what would cause it, could it be the blower resistor.

On my x244 the heater blower is fused at 30A, which makes that fuse the highest rated in the fusebox. We all tend to operate the blower for long periods while driving, summer and winter alike.
The heating effect of an electric current passing through a bad connection is proportinal to the square of the current, hence I^2R (I squared R), which term is often used to denote electrical losses in conductors and their connections.
If the quality of the connection deteriorates slightly the resulting heat can progressively increase the resistance of the connection by oxidation and loss of contact pressure.

I can see no logical reason why the blower speed control resistor would cause the problem, as it acts to reduce the current. Running the blower at higher speeds for longer periods would be a more likely cause, but we usually want the heat or ventilation.

Good clean connections to the fuse holder, and the fuse are essential, but on most fuseboards, the connections to the internal common busbars are not designed accessible for cleaning. There has been at least one fairly recent thread relating to the engine bay fusebox, where the possibility for moisture ingress is greater than in the cab.

Note to self. Pull green blower fuse and apply contact cleaner.

 

[Nickkdx]

On my x244 the heater blower is fused at 30A, which makes that fuse the highest rated in the fusebox. We all tend to operate the blower for long periods while driving, summer and winter alike.
The heating effect of an electric current passing through a bad connection is proportinal to the square of the current, hence I^2R (I squared R), which term is often used to denote electrical losses in conductors and their connections.
If the quality of the connection deteriorates slightly the resulting heat can progressively increase the resistance of the connection by oxidation and loss of contact pressure.

I can see no logical reason why the blower speed control resistor would cause the problem, as it acts to reduce the current. Running the blower at higher speeds for longer periods would be a more likely cause, but we usually want the heat or ventilation.

Good clean connections to the fuse holder, and the fuse are essential, but on most fuseboards, the connections to the internal common busbars are not designed accessible for cleaning. There has been at least one fairly recent thread relating to the engine bay fusebox, where the possibility for moisture ingress is greater than in the cab.

Note to self. Pull green blower fuse and apply contact cleaner.

I think my 2014 replacement fuse holder is beyond contact cleaner, you can see original also burnt , top right.
Also good you please tell where the common busbar as when I removed fuse board the wire came off. Cheers

 

[Communicator]

Oh dear! Another hot joint. Perhaps the blower bearings may have dried out, as they are probably self lubricating bronze bushes? Difficult to check. Perhaps try a larger physical size of fuse, either standard, or maxi blade fuse. However thais would mean carrying a dedicated spare.

The x244 fuse panels are different to those in your x230. The common busbars are folded metal sections with upturned fingers of similar size to the blades on the mini blade fuses. Connection to the supply side of the fuse is made by retained, symetrical double female connectors. In LH fuse panel, busbars include B+, IGN+ and LIGHTS+.

 

[airwave]

Hi, 2001 Fiat based Hymer motorhome,in 2014 I had the heater blower fan fuse melt the fuse hold on the fuse board so I bypassed the fuse board and fitted separate fuse hold and now that has melted as well , any suggestions as what would cause it, could it be the blower resistor.

Oh dear , err well i guess the best way to explain this , is it's a design issue , as far as i know on the x230 base , though i can't say , limited only to this model .

I replaced my fuse box about two , three years ago with exactly the same problem . I brought my Hymer back in 2017 , and though never noticed this during the pre purchase check , found it a couple of weeks later . It seems to be a common issue on the 230 base , caused by excessive use of the heater blower motor used in position 4 . It was something to do with excessive current causing enough heat to quite literally melt the fuse block . I never went too deep into this , as the way i understood it , it was a design issue and basically unrepairable . The best advice i can give , is do not use position 4 , of the blower motor for any great length of time , the fuse holder is basically not designed for this kind of abuse . There are fuse holders that can handle this current , but on that note i can't answer if the heater can or not . I also have no idea before anyone asks , if this is restricted to just the 230 , or whether any other models are affected . What i can say is , it was well documented on the net , with others reporting a similar problem .

Fuse blocks are difficult to source for these vehicles , and personally i searched for three years , until i eventually located one in a breakers yard in Lithuania . I did have a photograph of my fuse box , but seem to have lost it . I think it's on my other computer which had a brain storm , and died on me last year . I'm still trying to recover the pictures and music even now . Examination revealed the remains of two melted fuses , with the actual box badly burnt both sides of position 13 , incidentally a 30 amp blade position . I also found a bypass external fuse holder while working on the electrical system around the same time , ironically connected with 10 amp household connector blocks , when i replaced the original box . Disconnecting this , i reinstalled the heater wires back to their original positions back on the fuse block .

My own vehicle is a year 2000 , Hymer 584 , based on an x230 , 2.8 tdi chassis . It's been off the road for three years now , and due to return next year , after some pretty extensive work . Best advice , use the central heating , but don't use the cab heater for extended periods on position 4 .

 

[Nickkdx]

I very rarely use mine on 4 , this is on a 2001 Hymer B584
I’ve now replaced the fuse holder, hopefully it will last 7 years like the last one

 

[skiplightphil]

Oh dear , err well i guess the best way to explain this , is it's a design issue , as far as i know on the x230 base , though i can't say , limited only to this model .

I replaced my fuse box about two , three years ago with exactly the same problem . I brought my Hymer back in 2017 , and though never noticed this during the pre purchase check , found it a couple of weeks later . It seems to be a common issue on the 230 base , caused by excessive use of the heater blower motor used in position 4 . It was something to do with excessive current causing enough heat to quite literally melt the fuse block . I never went too deep into this , as the way i understood it , it was a design issue and basically unrepairable . The best advice i can give , is do not use position 4 , of the blower motor for any great length of time , the fuse holder is basically not designed for this kind of abuse . There are fuse holders that can handle this current , but on that note i can't answer if the heater can or not . I also have no idea before anyone asks , if this is restricted to just the 230 , or whether any other models are affected . What i can say is , it was well documented on the net , with others reporting a similar problem .

Fuse blocks are difficult to source for these vehicles , and personally i searched for three years , until i eventually located one in a breakers yard in Lithuania . I did have a photograph of my fuse box , but seem to have lost it . I think it's on my other computer which had a brain storm , and died on me last year . I'm still trying to recover the pictures and music even now . Examination revealed the remains of two melted fuses , with the actual box badly burnt both sides of position 13 , incidentally a 30 amp blade position . I also found a bypass external fuse holder while working on the electrical system around the same time , ironically connected with 10 amp household connector blocks , when i replaced the original box . Disconnecting this , i reinstalled the heater wires back to their original positions back on the fuse block .

My own vehicle is a year 2000 , Hymer 584 , based on an x230 , 2.8 tdi chassis . It's been off the road for three years now , and due to return next year , after some pretty extensive work . Best advice , use the central heating , but don't use the cab heater for extended periods on position 4 .

 

[skiplightphil]

Hi, 2001 Fiat based Hymer motorhome,in 2014 I had the heater blower fan fuse melt the fuse hold on the fuse board so I bypassed the fuse board and fitted separate fuse hold and now that has melted as well , any suggestions as what would cause it, could it be the blower resistor.

I have a Hymer B584 1999 and have taken thermal camera video of the blower fuse. The fuse definitely heats up more than the connectors and reached 107 C. On crimping the connectors tighter it reduced to 84 C. Not sure what to do next. I'm thinking I might put on new spade connectors to the fuse box, it's tight in there though with not much wire to spare.

 

[skiplightphil]

I have a Hymer B584 1999 and have taken thermal camera video of the blower fuse. The fuse definitely heats up more than the connectors and reached 107 C. On crimping the connectors tighter it reduced to 84 C. Not sure what to do next. I'm thinking I might put on new spade connectors to the fuse box, it's tight in there though with not much wire to spare. The blower draws 16A on setting 4.