big olga Posted January 5, 2012 Share Posted January 5, 2012 Hi, All. I hope you all have a wonderful 2012 with lots of trips away. I have a problem with the Heater Blower on the Mercedes 207d .I have checked the Internet for information to lead me in the right direction but the advice is always about cars. I have taken the switch out and checked it with the multimeter; it has power and restistance. I thought a fan should have a 25 amp fuse? can,t find one, or a big restistor.[two position switch] The only thing I can find under the bonnet is the device that is in the PICTURE which has no power or restistance on it.[with the ingnition on and the switch on] but I do not know if this is connected to the fan motor.[the hand book makes no mention of this item] I have looked at the plastic casing around the heater mounting but it looks like a major job to get the motor out [complete dasboard out!] I hope that someone will have an idea what this big ressistor does. Many Thanks "Big Olga" and Dave. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 6, 2012 Share Posted January 6, 2012 Does your motohome have a 'dim dip' headlght system - that is, when you turn on the vehicle's parking-lights with the vehicle's ignition also turned on, do the headlights come on at reduced light-output? Just a wild guess at the purpose of your mysterious device... Link to comment Share on other sites More sharing options...
neillking Posted January 6, 2012 Share Posted January 6, 2012 A bit of a pessimistic reply I'm afraid. We had a similar problem on the same vehicle some years ago and eventually eventually decided the problem was in the main assembly and that was too difficult to service so we added a number of budget 12v computer fans instead. The final version was two fans to the screen on one switch and two down to our feet on another, it actually worked very well. Good luck with your diagnosis, I hope you don't need the fans but if you do they can be found in the usual places, Maplin, RS Components, CPC, Car Boots, Computer Jumble etc. Link to comment Share on other sites More sharing options...
big olga Posted January 6, 2012 Author Share Posted January 6, 2012 hi, If I can,t find the fault I was thinking of cutting a hole in the rear of the plastic cover and installing a fan like the one you have discribed; with a seperate switch; to blow the hot air through the vents. Cold air is not a problem as the van has an air con unit on the roof but the lady of house likes hot air around her feet at this time of the year! Many Thanks for the replies. Dave. Link to comment Share on other sites More sharing options...
neillking Posted January 6, 2012 Share Posted January 6, 2012 When we did this a single fan didn't do it for us. Automotive fans are quite powerful compared with the normal computer versions - hence the multiples. Incidentally for ease of installation some of these were sucking out of the vent tubes rather than blowing through if you see what I mean. Link to comment Share on other sites More sharing options...
bob b Posted January 6, 2012 Share Posted January 6, 2012 Looking at the photograph of the device, it does look quite corroded. How about cleaning up the connections with some emery paper and see if that does anything. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 7, 2012 Share Posted January 7, 2012 I notice that there's a Peter Russek manual for the 207D: http://www.motorbooks.co.uk/notes.asp?bookid=68691 My experience of these booklets is mixed, but you never know your luck! I looked at the Haynes manuals for our now-scrapped 1995 VW Golf and our present Transit - the heater-motor could be removed from the former after minor dashboard dismantling, but the Transit's complete dashboard had to come out to replace the motor. Not a task I'd relish tackling. In Dave's case, as the heater-switch seems to be function as one might expect, I can't see what purpose the (rusty) device in the photo would have heater-wise. Having said that, as Bob suggests, cleaning the thing up shouldn't cause harm and might produce a miracle. Link to comment Share on other sites More sharing options...
big olga Posted January 7, 2012 Author Share Posted January 7, 2012 Hi, Derek, I have that hand book for the 207d but it makes no mention of this item; just covers general advice. I though a two speed fan would have a high value fuse but the ones I can find are 8amp fuses on the fuse box but what the three relays are for is also a puzzle. Many Thanks Dave. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 7, 2012 Share Posted January 7, 2012 big olga - 2012-01-07 1:56 PM Hi, Derek, I have that hand book for the 207d but it makes no mention of this item; just covers general advice. I though a two speed fan would have a high value fuse but the ones I can find are 8amp fuses on the fuse box but what the three relays are for is also a puzzle. Many Thanks Dave. I'd expect a heater-fan motor to be protected by a high-amperage fuse too - it's a 30A fuse on my Transit - are you sure there isn't another fuse box somewhere? I assume there's no way you can confirm whether or not 12V power is reaching the fan motor when the switch is turned on? It would be a beggar if there's nothing wrong with the motor and the problem just lies in the fan-motor's cabling. Link to comment Share on other sites More sharing options...
George Collings Posted January 9, 2012 Share Posted January 9, 2012 Via a magnifying glass the best I can do with the Russek manual is that the lead from the fuse to the heater switch is probably violet and two leads go from the switch to the fan, one is red and the other is completly unreadable. Typically the low speed feed is via a resistance, in this case it probably inside the motor as its not shown in the diagram. The earth lead from the heater is brown. As there appears to be 12V as far as the switch it matters not how the circuit is fused. Check at the heater if both leads from the switch are live when switch is operated. Check the the earth from heater actually makes a good contact. If you cannot find the earth connection rig a replacement. If all this checks out then the heater motor is probably dead. Traditionally vehicle heater designers are huge and very intimidating and have first say where their bit of equipment fits. Everyone else has to fit their gear on top. Rumour has it HM dockyards had a more democratic sytem. Each shift the different trades lined up on the dockside and raced aboard to the worksite, winner had the right to first pick of pipe or wiring run. Link to comment Share on other sites More sharing options...
Keithl Posted January 9, 2012 Share Posted January 9, 2012 George Collings - 2012-01-09 4:55 PM As there appears to be 12V as far as the switch it matters not how the circuit is fused. But also check that there is still 12v at the switch when the heater blower is connected and turned on as a faulty connection (corroded or loose) can show a voltage when not under load but fail when a load is applied. I know as I have been caught on on more than one occasion :$ Keith. Link to comment Share on other sites More sharing options...
big olga Posted January 9, 2012 Author Share Posted January 9, 2012 Hi, George, I have checked the switch by taking it out of the dash; it has resistance on the the two position switch; the wires are giving twelve volts so I think the switch is ok. I took the resistor unit out and found that the earth spade was rusty I cleaned it up and put the unit back and tried again ;still the same. I put the meter on the unit and found I had resistance on the wire coils in side the unit and had resistance on the earth LEAD but no resistance from the earth spade! I will take it out again and replace the earth spade for a new one. on page 198 of the book; section 9 it shows the motor and switch but I can,t get to the motor as it is encased in plastic. thank you to every one who has taken the time to reply to this subject. Dave. Link to comment Share on other sites More sharing options...
Keithl Posted January 9, 2012 Share Posted January 9, 2012 Hi Dave, It definitely sounds like this resistor is the fault. (I have also come across this same failure in the past on older cars). The problem is that the resistive wire heats up and cools down every time you use the blower and the 'wire' is a special kind to get a high resistance (can't remember the exact spec right now) and over time the surface scales up and prevents a good electrical connection. You will find the ends are crimped as this particular metal will not solder. The only option may be to try and un-crimp the ends then clean up the resistive wire then reconnect it possibly using a screw terminal to make a sound connection (a piece of choc-block perhaps?). HTH, Keith. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 10, 2012 Share Posted January 10, 2012 I hesitate to come back to this, but the idea that the mysterious 'resistor' shown in the photos has anything to do with the vehicle's heater is just based on the the premise (see the original posting) that a suitably heavy fuse for the heater could not be identified. I do'nt know how old Big Olga is, but UK 'dim-dip' lighting regulations were in place from 1987 to the mid-1990s and dim-dip systems used a hefty resistor to reduce headlamp power. I'm not saying that the thing in the photo is a dim-dip-related component, but I think there's a fair chance it is if Big Olga was marketed in the UK in the 1987-1995 time period. I note that Dave says that the 'resistor' does nothing with the ignition and heater-blower switches turned on, but it might be worth checking if something happens at the 'resistor' if the vehicle's motor is running and the parking-lights are switched on. As George Collings says, if there's 12V power on the input side of the heater-fan switch, then the fusing 'upstream' of that switch must be OK. And if there's 12V power on the output side of the switch, then the switch itself should be working OK. That leaves the cabling to the heater-motor and the earth connection to be investigated. George says that the Russek wiring diagram shows no sign of a separate resistor for the heater fan-motor and concludes that the low-speed resistance will probably be integrated with the motor. I would have thought this would be common practice and that it would be odd to deliberately choose to install a heater-motor resistance separately under the bonnet. Link to comment Share on other sites More sharing options...
Brambles Posted January 10, 2012 Share Posted January 10, 2012 From memory on this vintage of van the heater resistor is part of the motor assembly and stuck on the end of it and carries the main connector for the wiring. I may be wrong as is a long time ago I am recalling from. Somewhere in the heater assembly you should find a a connector plugged into the assembly hidden under the dashboard at the location of the motor. You really need to find this and unplug and test the connection for volts. I should add, it may not be a resistor as such, but a modulated regulator to control the motor power/speed. As Derek as said the resistor you are repairing is most likely the dim dip circuit. I have seen dim dip circuits which just put the lamps in series to dim them, but if a lamp failed it was detected by current through a relay and the resitor switched in to replace the failed filiment to keep the other lamp working on dim. Link to comment Share on other sites More sharing options...
big olga Posted January 10, 2012 Author Share Posted January 10, 2012 Hi All, I have found out what the item is THE RESISTOR FOR THE GLOW PLUGS! I found this out when I dismantled the thing to-day; inside I found a bi-metal switch;when i had it all back in and turned on the ignition the glow plug lamp came ON; then the penny dropped. I had changed the distance on the bi-metal switch , on my 32 year old van the light comes ON when the cylinders are heated ready for starting after 60 seconds. So the bi-metal is too close to the contact and completes the circuit too soon. on modern diesels the light goes OFF when the cylinders are heated. On a safety note I always disconnect the battery when I am working on the electrics. But this has still not solved the problem of the non running fan motor! So it is true you do learn something new every day! Best Wishes Dave. Link to comment Share on other sites More sharing options...
Guest peter Posted January 10, 2012 Share Posted January 10, 2012 Have you tried putting 12v directly to the motor and if it runs, work back from there. Link to comment Share on other sites More sharing options...
big olga Posted January 10, 2012 Author Share Posted January 10, 2012 Hi, Can.t get at the motor as it would take a complete dashboard removal to view it. The switch is live and the fuse is ok but no fan. Back to the drawing board! Many thanks Dave. Link to comment Share on other sites More sharing options...
Brambles Posted January 10, 2012 Share Posted January 10, 2012 Is there no way you can see with a torch where the cable connects to the heater assembly/motor and get hand in to discommect it? Link to comment Share on other sites More sharing options...
big olga Posted January 10, 2012 Author Share Posted January 10, 2012 Hi, the problem is the big lump of a diesel engine that is in the cab. the heater casing is above the engine so can,t get my head in to look up. I was thinking of cutting an inspection hatch in the motor casing from the top. Dave. Link to comment Share on other sites More sharing options...
Les Banjo Crocker Posted December 15, 2016 Share Posted December 15, 2016 I have an 87 207D motorhome with the same issue, by asking questions on the many groups that I am a member of, on Facebook, I discovered that the 207D is renowned for having heater motor issues, the main fault seems to lie with a common fault, this being that behind the scuttle panel, where the air vents are, they have a habit of corroding and allowing water to enter the vehicle and drip onto the heater motor and thus, burning it out, I have rectified the water ingress issue on mine, by cutting away, the vents and the air boxes, (which are all steel ) and were completely rotten and then re fabricating them in sheet aluminium, then, replacing the original vents, with aluminium, surface vents, I too, need to remove the original motor and either replace it with a new one, or get the original, refurbished. don't fancy taking the dash out but, if needs must, at least, it will be an opportunity, for me to inspect the condition behind it, a good tell tale sign of corrosion behind the scuttle panel is, the presence of a wet floor inside the cab Link to comment Share on other sites More sharing options...
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