'Hot ceramic tube' - Help! - anyone?
Discussion
This has got me puzzled - I'm not too good at electrics. (1991 450SE Hot wire)
During the run back from Goodwood last Sunday, a piece of trim dislodged and slipped down over the carpeted passenger side of the transmission tunnel, just to the rear of the central dash.
Got home and prepared some new velcro strips to hold in place, noticed scorch marks on the rear face - turns out to be this tube with wires soldered to each end. It heats up when the heater blower motor is on. It gets very hot (I got burnt fingers
)so potential fire hazard here!
The tube looks to be made of ceramic and it's hollow, about 50mm long, 15mm dia. grey wire attached one end and 3 wires other end - yellow, blue and another yellow. All of these wires (apart from one yellow) go to a connector block. other end of this conn. block are 3 wires blue/red, blue/white and a black.
Anyone know what this tube is for, what is its function?
Why is it getting this hot?
Any information, greatly appreciated!
Cheers
>> Edited by The Colonel on Wednesday 8th March 20:39
During the run back from Goodwood last Sunday, a piece of trim dislodged and slipped down over the carpeted passenger side of the transmission tunnel, just to the rear of the central dash.
Got home and prepared some new velcro strips to hold in place, noticed scorch marks on the rear face - turns out to be this tube with wires soldered to each end. It heats up when the heater blower motor is on. It gets very hot (I got burnt fingers
)so potential fire hazard here! The tube looks to be made of ceramic and it's hollow, about 50mm long, 15mm dia. grey wire attached one end and 3 wires other end - yellow, blue and another yellow. All of these wires (apart from one yellow) go to a connector block. other end of this conn. block are 3 wires blue/red, blue/white and a black.
Anyone know what this tube is for, what is its function?
Why is it getting this hot?
Any information, greatly appreciated!
Cheers
>> Edited by The Colonel on Wednesday 8th March 20:39
350matt said:
Its the resistor for the heater blower motor, on the low speed settings the current has to pass through the resistor 1st and so it heats up and reduces the power to the blower motor making it run slower
crude but effective
Matt
I always run the blower on the low speed setting, never the higher speed (too loud!)
So does yours get hot enough to melt any wiring that came into contact?
As already said it's a resistor for the slow fan speed.
It's not in circuit when the fan is switched to fast speed so won't get hot unless you use the slow speed.
IIRC the last time I had my head up there I saw an extra tapping on the resistor which if used would provide an extra speed setting though there is no extra switch position. If you try both options for slow speed and select the faster one, this will result in the resistor running cooler as it is dropping less voltage.
It is not unusual for ceramic resistors to run hot enough to burn skin. They are designed to drop voltage and hence need to be able to dissipate the heat generated.
I doubt this is a serious fire risk but if your worried then try moving parts around so the resistor is surrounded by air and not touching cloth. Allowing air to circulate will let it run cooler.
It's not in circuit when the fan is switched to fast speed so won't get hot unless you use the slow speed.
IIRC the last time I had my head up there I saw an extra tapping on the resistor which if used would provide an extra speed setting though there is no extra switch position. If you try both options for slow speed and select the faster one, this will result in the resistor running cooler as it is dropping less voltage.
It is not unusual for ceramic resistors to run hot enough to burn skin. They are designed to drop voltage and hence need to be able to dissipate the heat generated.
I doubt this is a serious fire risk but if your worried then try moving parts around so the resistor is surrounded by air and not touching cloth. Allowing air to circulate will let it run cooler.
350zwelgje said:It takes very little resistance to cause problems with 12V so check/substitute/replace the switch, wiring and crimp terminals. From your description of the fault it is unlikely to be on the motor side of the switch so concentrate on the switch, resistor, and interconnections thereof.
While on the subject. My fan works on the low setting and not the fast 'extra strong'. It all happened over a few minutes: first low not working, fast ok. Then fast died, low is ok and stayed like that. Any ideas?
Rob - '87 350i
Normally when you have only one or no fan on heater it's the switch contacts on the dash switch. Take apart clean bash with hammer, runb with emery cloth and eventually you may get all speeds back
Well it work for my 2 wedges at some point in there live. Probably just as cheap to buy new switch, but not many shops seem to be open when you need to demist your screen in a hurry on a cold wet day in Le Mans !
Well it work for my 2 wedges at some point in there live. Probably just as cheap to buy new switch, but not many shops seem to be open when you need to demist your screen in a hurry on a cold wet day in Le Mans !
matt-man said:
not a very successful run back from goodwood for electrics then eh colonel!!...
As it turned out, if I had stopped at the bottom of the hill to keep your wedge company mine would have been a non-starter as well!
I think you mentioned RAC attended yours, mine was AA, what a great photo oppertunity missed - could have entered it for Sprint mag photo competition
matt-man said:
good job your 'wedge driving brain' over took the 'lets be kind and stop' part of your brian then!!
I have a funny feeling im going to get my moneys worth! I only renewed my RAC last week! PHEW!
I actually do feel bad about not stopping - honest!
But I blame Mrs Colonel for saying to me the Ultima was in attendance!
- and yes I will be taking her along to Specsavers
What's the best value accessory that you can buy for your Wedge? - Breakdown cover!
Gassing Station | Wedges | Top of Page | What's New | My Stuff