KeithR Posted July 30, 2007 Share Posted July 30, 2007 on a recent trip abroad, during a severe downpour, i found my cab misting up. the fan heater/blower/demister seemed to have died. i checked any fuses i could find, but all seemed well. after the downpour the fan seemed to be operating ok. a couple of weeks later the same problem occurred. as a mechanical dyslexic i appeal to all you knowledgeable experts out there for help. what could be the problem? where do i start looking (i dont even know where the fan is!)? anyone ever had a similar problem? the vehicle is a 2004 fiat 2.8jtd. i admit that in my haste to see the road i did twizzle twist and push all the knobs in all sorts of combination! but apart from these 2 recent occurances the fan has behaved itself. keithr Link to comment Share on other sites More sharing options...
Vernon B Posted July 30, 2007 Share Posted July 30, 2007 Hi Keith. The great thing about this site is that there'll be someone out there who can help you. Although I'm not your man it will help other's if you provide a bit more info:- Is your van a "conversion" a "coach built" or an "A-class"? Does it have cab air conditioning? Vernon Link to comment Share on other sites More sharing options...
davenewellhome Posted July 30, 2007 Share Posted July 30, 2007 Hi Keith, there is no logical reason that I can see for your fan to pack up when its raining. Are you sure it wasn't working? Could it be that the fan was working but just not clearing the condensation? Did you pull over and check or just fiddle about while still driving? Sorry if that sounds a bit rude but if you were still driving you might not have been looking closely at the fan controls (besides which if you were still driving with a badly misted up windscreen in heavy rain I have to ask was your vision not impaired?) D. Link to comment Share on other sites More sharing options...
KeithR Posted July 31, 2007 Author Share Posted July 31, 2007 no, i dont take exception to your comments, i'm sure my post was a bit vague and confusing (i was at the time! and still am!!). my moby is an LP coachbuilt (adria 650). yes dave, i too thought that i had just 'dialled' the wrong combination, but when it happened the second time i was sure the air blow had died. could the conditions have been a coincidence? and there is an intermittant fault? keithr Link to comment Share on other sites More sharing options...
BrianR Posted July 31, 2007 Share Posted July 31, 2007 If your Sevel built Fiat is similat to my Sevel built Peugeot, the fan is just under the windscreen, in front of the passenger, behind the dashboard. You can see the "back" of the housing under the bonnet. It sounds to me as if water is getting in to the elctrical connections when it rains and breaking the circuit, without actually shorting it out (as the fuse is not blowing). On the other hand, are you sure that it is not stopping working on other occasions, but you are just not aware of it? Brian Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 31, 2007 Share Posted July 31, 2007 KeithWith respect, as they will say, you haven't answered Dave's question! What, apart from the misting screen, made you think the fan had stopped working?If it was a warm, even muggy, day before the rain, it is probable the air inside your van was also warm and a bit humid. With the heat of the day, the windscreen will also have been fairly warm. Warm - even moist - air + warm glass = no condensation. Rain, however, is relatively cold, and so, in falling on the windscreen, will chill it. Despite the rain, the external air will have remained generally warm and muggy, and the blower will have been sucking that into your van and blowing it up the cooled screen. Ipso, the moisture in the warm air will condense onto the cooled screen. Warm, moist air + cool glass = condensation. The faster you run the fan, the more air you deliver to the cool screen, and the worse the condensation gets. If you turn the heater control to max, the fan to max, and set the blower to de-mist, it will eventually win, warm the glass and evaporate off the misting. However, it will take ages and roast you at the same time! By heating the air further, its relative humidity will be reduced, and it will also warm the screen a bit. Hot dry air + warmed screen = no condensation.The real solution to de-misting under these conditions is, I'm afraid, cab airconditioning, which dries the air out as it chills it, so you get cool dry air being blown onto the cool glass. The relative dryness of the air removes any misting, and the fact that it is cool and dry ensures no more misting forms. Cool dry air + cool glass = no condensation.Obviously, none of this can work if the fan isn't blowing; but what you've described seems about right for what normally happens to a windscreen on a hot muggy day when it suddenly rains - without cab aircon - even if the blower is going full tilt! Link to comment Share on other sites More sharing options...
KeithR Posted July 31, 2007 Author Share Posted July 31, 2007 i tend to have the blower on all the time brian, and at the time of these failures the temp was v. hot, so the cold blow was definately on! Link to comment Share on other sites More sharing options...
KeithR Posted July 31, 2007 Author Share Posted July 31, 2007 i've seen your technical know how many times on here brian, and bow to your knowledge. the conditions were as you said, hot and muggy, with nasty little rainsqualls (cant avoid 'em even after calais!). but i am sure there was no blow. mine is a left hand drive, so will the fan be on the other side, and is it easy to get at? i have nightmares at the thought of dismantling my pride and joy! Link to comment Share on other sites More sharing options...
davenewellhome Posted July 31, 2007 Share Posted July 31, 2007 Keith, you still have not answered my questions. Did you pull over to sort out the heater blower and establish that it was definitely not moving any air? D. Link to comment Share on other sites More sharing options...
martin r c Posted July 31, 2007 Share Posted July 31, 2007 With just the ign on and nothing else, can you hear the fan running. (?) Martin Link to comment Share on other sites More sharing options...
KeithR Posted August 1, 2007 Author Share Posted August 1, 2007 sorry dave, i'll try to be a little more precise. the blower is always on, with the dials set to blow at dash and foot. when the squall hit i adjusted the dials to direct the blow to the screen, and put it on full (it usually is at 3). as there seemed to be little or no effect i adjusted everything whilst i drove (okay, i'm a bad lad!!). after a while i pulled over and looked under the bonnet (remember, i didnt really have a clue what i was looking for!) in the hopes i could see/hear something, maybe a pipe/ducting hanging, a pool of water perhaps near a fuse box, but everything seemed in order. i must then have stopped the engine, as i got the handbook out and tried to find the fuse. it was con-fuse-ing, as there were a number of fuses that dealt with the heating and air con (which i dont have), so i checked all the fuses in the 2 fuse boxes under the bonnet, and the fuse box in the cab. all seemed ok. fortunately, whilst i was out of the van, the weather abated, and when i set off again i think the fan seemed to be working. i put it down to either the rain, or a dodgy fuse (i had removed and replaced them all). i think that sequence is correct, although i was blowing my own fuse by then and not thinking straight (or thinking at all!) it was all fine untill about 2 weeks later that it happened again, but i cant remember exactly the events. as the fiat is quite noisy, and my hearing is showing my age, (thus the radio is on quite loud), I cant say that i noticed the fan running. or does that point to the fact it wasnt??? i dont think im giving you guys much to go on am i?? i will rtakle the van for a run in the next few days and see if i can hear the fan, check exactly where the dials are, and try to find a rain squall (that should be easy!) :$ Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 1, 2007 Share Posted August 1, 2007 KeithI think the problem is as I described above. Warm muggy air being drawn from outside, and condensing on the rain cooled screen. Then, when you turned the control to the demist position, you merely squirted more warm muggy air straight up the rain cooled screen, so it added to the condensation rather than curing it. Then, you probably turned the heater control up, so that you further warmed that already warm, muggy, air. Problem is, the warmer the air the more moisture it can carry. Short term result: even more condensation! If you are unsure about the fan, do as suggested above and turn on the ignition without starting the engine, and then play around with the blower and heater controls. I suspect that you'll find the blower keeps going and, without the engine running, you should be able to hear it clearly. If still unsure, get someone to direct a hose at the windscreen while you do this, and see if the fan falters at any time as you put it through its paces in simulated rain. However, I think the most likely explanation is that this was just one of those combinations of conditions that vehicle demisters just can't handle all that well! Link to comment Share on other sites More sharing options...
KeithR Posted August 2, 2007 Author Share Posted August 2, 2007 thanks brian, you may well be right. i must check it further, and be more precise about what happens and what i do, then perhaps there will be something concrete for the experts to work on. thanks everyone for your input, happy touring. Link to comment Share on other sites More sharing options...
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