Heater fan problems on 2.1 WBXDJ

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Mr Bean
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Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

The three position heater fan switch seemed to be jamming then stuck in one position but could be moved over to run heater full chat if held there. Clearly switch jammed or coming to bits inside. Familiar bang like flap closing in nether regions of heater. So I went for the PWM mod successfully as I initially thought Using the existing (red/black if I remember correctly) wire in loom which incidentally only powered when ignition on which kind of puzzled me but has worked for about ten years with me. Last check before tidying up and putting tools away and the wire went dead. Checked all fuses in glove box and all good. spent some time sussing in Bentleys and Haynes and got lost in the track lines etc. So tested with remote battery and all good so put ran a new fused wire from the battery and all runs fine except it will eventually blow a 10A fuse on fan full bore plus I don't hear that flap closing any more. So I now have a dead red/black wire which doesn't seem to feed anything else and a fan motor which clearly is borderline for 10A at full bore. Although the fan blows well I wonder if high current is a symptom of impending failure. I am not in the right frame of mind for a dash out job at this time of year (if at all :cry:)
Two questions:
1/ What about the original feed? the manuals say Fuse 13 but that is good and I haven't found anything else which doesn't work.
2/ Anyone know what their fan draws in current?
CS
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Re: Heater fan problems on 2.1 WBXDJ

Post by bigherb »

Heater fan power supply cable is black/red (red/black is the starter energising cable)

New fans draw around 12A on full chat, increasing as they get older hence fuse 13 is 25A
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

Thanks for that bigherb. I had a fresh look through my Bentley this morning and discovered a heater fan circuit with a BK/R feed - page 97.66 water cooled Digijet 1985 period. My van being 1988! Although that BK/R gets its supply from fuse S10 - 16A which also feeds windscreen wash/wipe circuits which still work so that doesn't look right. I can't find anything which doesn't work on the van so unless there is a fuse somewhere other than the glove compartment I am stumped. As previously stated I have the PWM device connected independently direct from the battery via an in-line spade fuse holder and it now runs OK so far on a 15 A fuse - the 10A fuse failing after a while. I would be rue to go up to 25 A fuse and so will leave things as they are until I can find an open circuit further into the BK/R circuit or matbe a fuse hiding somewhere elsewhere than the glove box.

Recapping: The fan has been fed via that BK/R wire for at least the ten years I have had the van and failed in at fan full bore while testing via the PWM controller. All the fuses in the glove compartment are good. The new circuit (independent of fusebox) blows a 10 A fuse but runs OK on a 15 A fuse which fits in with the 12 A quoted which sounds OK for my fan motor although on the edge. There is a whole lot of info in those wiring diagrams so I am not absolutely sure I am looking in the right place. I think I have done this to death for the moment but it will niggle at me until I get it sussed.

CS
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Re: Heater fan problems on 2.1 WBXDJ

Post by bigherb »

The fresh air blower/heater is supplied by fuse 13 20A
Warm air blower is the rear heater.

V2 is the blower E9 the switch.
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

Thanks for that BH it clarifies what I have found. Where does that circuit diagram come from?
As my fuse 13 has not blown but but I still have no volts on sw/ro (black/red) to A 22, I guess I need to test for continuity between fuse 13 and the sw/ro (black/red) wire where it exits the loom under the instrument cluster. I guess there is a connector at or behind the relay plate which could be open circuit although when I undid the cross head screw at the bottom the relay and fuse block was reluctant to pull out or fold down for me to check the rear to see the other end of the sw/ro (black/red) wire where it terminates to the fuse. I was concerned that I might disturb something and introduce another problem.
The very useful information which your latest post gave me is that nothing else is fed from that fuse. So unless I find an easy cure for the apparent open circuit I can safely leave my bypass wiring in place without worrying about what else might be not be working. Although I am still puzzled about how the wire was only live with the ignition on. Unless track X is energized via a relay fed from the ignition circuit at which stage Her Ladyship would accuse me of overthinking the problem :roll: .
Thanks again
CS
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Re: Heater fan problems on 2.1 WBXDJ

Post by CovKid »

I do make this clear with reference to the PWM upgrade that it should not be fitted to an old fan motor as the draw on an old motor can be excessive. An old motor also puts load on a stock system with the 3-position switch and dropper resistors, but could also damage a PWM controller (even if easier to replace than resistors). Upgrading won't change any existing motor load issues.

Also, earlier T25s had wipers and blower on the one fuse as you've discovered, and I penned how and why to split those in the WIKI. Anyone with both on one fuse should always split them to avoid loss of wipers on a very wet day. I'm sure you're aware of all this but adding this note so others are aware.

Finally, for those thinking of attempting to free a seized or partially seized blower motor by drilling a hole through the front behind headlight grill to spray WD40 in there in a vague hope of re-lubricating it, don't bother. Its an absurd 'solution' and whoever posted that on the Samba wants shooting. An old electric motor is an old electric motor. Once they start to fail or draw way too much current, replacement or overhaul is the ONLY answer. They can become a fire hazard very quickly when bodged.

Back to your problem. Until you can get dash out in warmer weather, just make sure fuse is sufficient. 25amp is a wise value in this instance. Don't fear getting the dash out though. It really isn't hard, its more about determination and comes out a lot quicker than you might think.
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

I seem to be getting away with a 15A fuse and have extended the wires so that should it blow I can replace it easily so I suspect the motor is fine (I may have replaced it when I refurbed the van).

I have other problems higher on the priority list however which include replacing the exhaust system which has been fitted with bolts rather than studs one of which is already stripped and fixing a slow drip from the gearbox end of the driveshaft to name a couple.
I did have a fright coming home on the M3 last evening when the flashing light of doom activated. Although after unloading the bedding and luggage from the engine cover I found that coolant was slowly being forced up the header tank sensor and the cooling system was operating correctly. As I had purchased it less than a year ago the supplier is sending a free replacement.
I remember reading about a flashing red light of doom on the forum and had associated it with the lubrication system. Is there another FLD:
CS
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Re: Heater fan problems on 2.1 WBXDJ

Post by CovKid »

Thats how to fix leak at gearbox :) http://wiki.club8090.co.uk/index.php/Ge ... eak_repair" onclick="window.open(this.href);return false;
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

Thanks Covkid. Top job. This forum is a godsend to the afflicted. :ok
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Re: Heater fan problems on 2.1 WBXDJ

Post by ghost123uk »

Citizen Smith wrote: I remember reading about a flashing red light of doom on the forum and had associated it with the lubrication system. Is there another FLD:
Lubrication warning system covered in our "wiki" here = http://wiki.club8090.co.uk/index.php/Al ... and_causes" onclick="window.open(this.href);return false;

Coolant warning system covered here = http://wiki.club8090.co.uk/index.php/Co ... ht_on_dash" onclick="window.open(this.href);return false;
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

Yes come to think of it I did have an FLD experience when stuck in traffic while trickling down a steep hill in in a heat wave.
Thanks again.

CS AKA Aflicted :ok
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Re: Heater fan problems on 2.1 WBXDJ

Post by ghost123uk »

Got to ask, what does "FLD" stand for?
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Re: Heater fan problems on 2.1 WBXDJ

Post by R0B »

Short for flashing light of doom methinks.
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Re: Heater fan problems on 2.1 WBXDJ

Post by Mr Bean »

Yes sorry about that. Lazy fingers I guess.
CS
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