Zel's Fleet Blog - BX, Jag XJ-S, Sinclair C5, Mercedes 208D & 230TE, AC Model 70.

[xantia_v6]

Are you sure that your car has an electronic fan speed controller? I had a 1985 XJ-SC and I am sure that it had the relays and resistors. My understanding is that the electronic (Mk3) version was introduced in the XJ40 in 1986 and then the XJ-S a year or so later.

I did not really describe how the water valve is controlled. The water valve is normally open and is closed by vacuum on the bellows. It is controlled by a vacuum valve on one of the cam lobes on the servo assembly. The vacuum is only applied (water shut off) when the servo is at more than about 75% cooling, which is roughly when the fans switch from speed 2 to speed 3 (of 4) but a bit before the recirculation flaps open.

Random and sudden changes in airflow are usually caused by a vacuum leak, often because one of the vacuum hoses has come adrift, and leaks lots of air when the corresponding valve opens. It is also worth checking the plastic non-return valve near the washer reservoir, as these get sticky and don't open properly, making the vacuum system behave strangely.

[Zelandeth]

Are you sure that your car has an electronic fan speed controller? I had a 1985 XJ-SC and I am sure that it had the relays and resistors. My understanding is that the electronic (Mk3) version was introduced in the XJ40 in 1986 and then the XJ-S a year or so later.

I did not really describe how the water valve is controlled. The water valve is normally open and is closed by vacuum on the bellows. It is controlled by a vacuum valve on one of the cam lobes on the servo assembly. The vacuum is only applied (water shut off) when the servo is at more than about 75% cooling, which is roughly when the fans switch from speed 2 to speed 3 (of 4) but a bit before the recirculation flaps open.

Random and sudden changes in airflow are usually caused by a vacuum leak, often because one of the vacuum hoses has come adrift, and leaks lots of air when the corresponding valve opens. It is also worth checking the plastic non-return valve near the washer reservoir, as these get sticky and don't open properly, making the vacuum system behave strangely.

Interesting. I've no idea what type of speed control is used, was just sure I remembered reading that the switchover to the electronic speed control coincided with the launch of the HE.

Looking at my photos of the general area yesterday, this does look like it could be a likely candidate for a speed switchover relay block to my eyes based on your description of the location.



A bit of experimentation today showed signs of life from all parts of the system as we'd hope based on your earlier advice. The only notable exception being the hot water cutoff valve which never appears to be allowed to open. Even after the engine had been running for 15 minutes or so and the heater temperature set to maximum and the blower to high, it was still held closed by the vacuum actuator. Investigation needed.


Bearing in mind that it was raining this morning, walking up to the car and finding only this by way of signs of condensation definitely seems a positive indication compared to yesterday...



Footwells are bone dry save for a bit of residual damp from the annoyingly glued in place carpet I can't remove.





I'd really like to get my dehumidifier set up in the car and leave it running for a few days to get the carpets I can't remove etc properly dried out, sadly the fan on it has seized so I need to pull it to bits to revive it at some point.

I only had half an hour today before the daylight failed, so was mainly checking for signs of further water ingress...however while I was there I snapped a few photos mostly for Jim's benefit to demonstrate just how much stuff is crammed in behind the dash in this contraption.



The black rectangle attached to the blower body is one of about half a dozen fuse boxes scattered seemingly at random around the car.



Pulled the instrument panel yesterday to see if that would give me better access to get that annoying plenum back in place...the answer being "no" unless I want to remove the brace holding the steering column to the bulkhead. The blue thing several layers back is the offending item I'm trying to get back into where it lives. Even with that bracket out the way I don't think it would help me much as that wiring loom behind it is as solid as a rock.



At least getting the instrument panel out is pretty easy courtesy of it being a fully electronic panel so there's no speedometer cable to worry about and the reach adjustment on the steering wheel means getting it out of the gap is easy enough.

The moment you look down however you get to see the haphazard mess of relays in the general vicinity of the fuse box. Not sure if these were originally clipped in place some how...



Despite the penny pinching, nice to see they didn't skimp on RF suppression on the brake light switch!



Though I get the impression that switch probably contains 50% more moving parts than is really necessary.

In the passenger's footwell there's a second fuse box, another blower assembly and more relays. Some nice and neatly clipped in by the fusebox...others just...well stuffed behind the trim seemingly at random.



The whole push/pull arrangment for the bonnet release/lock means even the handle for that is overcomplicated.

Had wondered how far up the HVAC assembly I could see from down there...answer being "Not very" I think, so I'll probably need to pull the glove box out if I need to get to anywhere up there.



Just noticed looking at the photo, I do indeed spy an old Econocruise control box...there's a blast from the past.

It seems to be the same story basically behind any bit of trim you remove in this car...there's just "stuff" behind everything, including in the boot (which is where the injection ECU lives).

I think the HVAC control system probably gets the award for most overcomplicated design though. I mean you couldn't just have stepper motors, tiny servos or vacuum control...you had to have ALL of the above in one unit...I'm sure it made sense to somebody!

EDIT: Tyres have been ordered. Hopefully I'll be able to arrange a fitting date shortly.

[xantia_v6]

The vacuum signal to the water valve comes from one of the 2 vacuum valves that are actuated by the servo cam (the other controls the centre facia vent). It is possible that something is loose on the servo assembly, but it is a bit fiddly to remove the servo assembly (especially the first time you try), and when you refit it, you need to re-calibrate the flap control rods. It is possible that someone has connected the water control valve to the wrong vacuum line. For now it should be safe to disconnect and block off the water valve control line and diagnose the rest of the system.

[xantia_v6]

This is the view with the glovebox removed.

The coloured wires near the centre of the picture are going to the fan speed resistors, the 2 wires going down are for the water temperature switch. The rods and levers on this side operate the centre vent.

The hose that is obscuring the temperature switch is the hose to the in-car temperature sensor, and the metal T-piece at the left hand end of it is the venturi that creates the (slight) vacuum to suck air past the sensor.

My photo, my car...

[Zelandeth]

Thanks for that, if the water shut off valve vacuum signal and the centre vent are connected the servo responsible could well be the culprit as I've never found any particularly useful airflow from that vent, though I've no real reference for how good or not that should be...the view of what's up top is really handy too.

Really useful information for someone just delving into this for the first time.

Hadn't really intended to get into a huge HVAC trouble shooting round here, just wanted to take a quick look for anything obviously amiss and see if I could get a working screen demister. Right up to the point that stupid plenum fell out!

It'll be getting partly put back together shortly either way as it'll be needing to go get tyres fitted.

The question does come back around though...how *DO* you get that plenum back onto the blower? I have a horrible feeling I'm going to have to faff around removing the blower and the resulting arguing with flaps to get it back in aren't I? It just seems to be a snug enough fit that I really can't see how you'd ever get it in place in situ.

[xantia_v6]

I think that I did manage it with the blower in-situ, but vowed not to do it again. It is a while since I removed a blower assembly, but I don't think it is quite as difficult as it looks. You may as well try to lubricate the bearings while you are there...

[CitroJim]

Zel, you are one very brave man! And I thought replacing a Xantia heater matrix (and indeed the full heater box) was a bit of a challenge but this eclipses it by several orders of magnitude

The complexity is breath-taking

I continue to watch the 'Battle of the blue plenum' adventure with great interest... Edge of the seat stuff

I know you'll succeed

[Zelandeth]

Not a bad idea to get some oil onto the bearings to be honest, especially given that I know that not insubstantial amounts of water have been through the blower assemblies courtesy of the blocked scuttle drains. As I recall they're plain bronze bearings on these aren't they, so typical light machine oil is probably the order of the day. Getting the blower out doesn't look *too* bad a job, just an annoying one as there's a bunch of stuff bolted onto the bracket holding it in (because of course there is!), and it's fiddly because of the way the air distribution flaps are interlocked...though I think that's more of a nuisance when getting it back in than out. Will need to dig back out the guide I found on that when I was looking for inspiration on how to get the fluffing plenum back on.

This car suffers very much from the "designed by committee" problem I think, where no one department or design team ever actually spoke to another directly. There's no *reason* for quite a few areas being half as complicated as they are, nor routine tasks being as awkward as they actually are. Also of course the classic bean counter involvement resulting in some truly "interesting" component choices from the existing parts bin rather than something new actually fit for purpose being made. The coolant expansion catch tank buried in the inner wing using what looks to be a 1970s generic parts store washer bottle to collect the coolant I think is my favourite on in that category so far.

That said, there are no shortage of "interesting" engineering decisions as well. The whole "1 1/2 pass" flow through the radiator with the feeds set up such that one bank of cylinders invariably runs warmer (with the temperature gauge sender on the cooler of the two banks of course!) sticks in my mind as one of the best "why on earth did they do that?" examples.

Edit:

Think I may just have found a smoking gun with regards to the slight but annoying damp that seems to be getting into the Xantia (just enough to make the windows instantly steam up whenever it rains).



Will pull and re-seal that tail light and see if that cures it. All of the water off the rear of the roof and tailgate runs over here and there's a seam between two panels under the seal so it's a prime candidate for water ingress even though the actual void into the interior is pretty tiny (just a passthrough for the wiring) as I recall.

[xantia_v6]

That said, there are no shortage of "interesting" engineering decisions as well. The whole "1 1/2 pass" flow through the radiator with the feeds set up such that one bank of cylinders invariably runs warmer (with the temperature gauge sender on the cooler of the two banks of course!) sticks in my mind as one of the best "why on earth did they do that?" examples.

That common internet wisdom regarding the XJ-S radiator does not really stand up to scrutiny.

The radiator has only one outlet, and it feeds, via the water pump both banks of the engine, so the temperature of the water going inot each bank is the same. Each bank has a thermostat independently controlling the temperature on the way out, so there is reaally no mechanism by which the radiator can influence the relative temperatures of the banks.

It could be argued that the design of the radiator is actually more efficient than any other because injecting the output of half the engine half way down the radiator increases the average temperature of the lower half of the radiator, increasing its heat transfer capacity for the same surface area.

[Zelandeth]

Now you mention that it's blindingly obvious that what you say of course makes sense...Irrespective of where the flow into the radiator comes from, if there's only one return into a single water pump *of course* the water's going to be at the same temperature throughout. That's what I get for believing everything read in that XJ-S help guide without engaging my brain. It's still a strange system...though yeah, not as flawed as it might sound.

A quick common sense question. I'll need to be dropping the car off to get two new tyres fitted at some point in the next few days. As the garage have no waiting area currently open and there's strictly no access to the workshop because of Covid, I simply have to leave the car there and come back later. Have to admit that I am tempted to just take the wheels in question over and just have them swap the tyres over on that.

Biggest issue is that I've had plenty of cars where the sills have been damaged by careless jacking of the car. Suffice to say the idea of jacking a 1700kg car with more than half a tonne of drivetrain up front from a sill made from 34 year old British steel fills me with dread...but I know full well that if I don't leave VERY SPECIFIC instructions that's inevitably what they'll do. ...It's a random tyre fitting centre I've not used before so it's entirely likely they'll do it even if I do leave instructions to be honest.

What is the best location to advise them to jack the front of the car from? I can't remember where I lifted it from when I did the oil filter (granted, didn't get the car off the ground then anyway, just got it high enough to get an axle stand in somewhere and to reach the filter), and crawling around outside in the weather right now doesn't sound like my idea of fun!

[myglaren]

Print some big red arrows with "Jack Here" on them to stick near the correct locations.

[admiral51]

Could you get them to come to you ?

[Zelandeth]

Could you get them to come to you ?

I did look at that but the services offering that were either £20+ more per tyre and/or didn't have slots available anywhere this side of mid December. Just irked that my usual tyre place didn't have anything suitable available.

If I'd had my brain engaged at the time I'd have just had the tyres shipped directly to me and taken them over there to be fitted...but I was on about iteration twelve of trying to make this work by that point so completely failed to realise that was the sensible option until several hours after I'd ordered things. I'd been having a lot of issues with the website and was getting well frustrated with the whole process by that point.

[admiral51]

Sorry Zel it was a quick reply from my phone.
Reading back i think you have bought the tyres and got them delivered to a place where they are going to be fitted, could you not collect the tyres (already paid for) take them home and then get someone to fit them, you only pay for fitting if they fit them ?
Our firm ( Lorries ) use Truck Tyre but we get them to fit car and van tyres at our yard, we pay callout charge etc but they do fit our own tyres ie not supplied by them.
Yes in your case it may cost a little bit more than what you had costed but you can watch/monitor what they do jacking point wise etc

[Zelandeth]

Thing is with the current situation I don't know if things would be any better at my usual garage...they're not above doing stupid stuff, just I feel like enough of a regular there that I don't feel bad generally floating around and making the odd suggestion if necessary. They're usually sensible though.

It's very much an unnecessary journey though from one side of town where the tyres are being delivered to, all the way to the very farthest point where my usual tyre fitter is.

Really do miss having access to the tyre fitting machine when I worked at a garage...that's something I'd really love to have in the corner of my garage. Just a really handy thing to have access to.

Guess I'll see what sort of vibe I get from the place when I arrive. If they don't strike me as a classic friendly place I may well just grab the tyres and have them fitted elsewhere. If they seem okay we'll see how they do.

ADDITIONAL: So yesterday evening I ended up wasting the best part of three hours getting a clean print out of this thing.



For the third time in as many months.

If you use it at least once every couple of weeks it's as good as gold. Print quality is second to non, I've printed about 1500 pages and am still on the ink bottles that came in the box and I don't think I've ever had a paper jam. However it's still an inkjet...so it still gets cranky if left unused for any length of time. Well... except for the old HP PSC2179 which we still have in my husband's room that I bought back in 2003...it seems strangely immune to that problem even if left for six months at a time.

I've just had enough of consumer grade printers. I went out of my way to get a decent one when I got the ET4550, and it's still trouble.

After a bit of digging around I've just ordered a reconditioned HP4600dn. Proper enterprise grade colour laser from 2002. I have prior knowledge of this exact model as it's the one printer that even the council roads department couldn't kill...which is high praise for any piece of equipment! Don't think that one was ever out of service from 2005 through to 2012 when we moved buildings. £120 for a reconditioned one with warranty, brand new imaging kit and transfer belt, and toners showing minimum of 40% (they're good for 8000 pages so that'll last me plenty anyway!) sounded like a bargain to me.

Nice that because this is a belt transfer based printer it prints all four colours at once so performance is identical when printing colour or monochrome. A lot of smaller colour lasers from this sort of period used sequential colour printing...so colour print speed would be 1/4 that of mono. The one in our office did about 15ppm mono...but 3 in colour...and it took a good 45 seconds for the first colour page to appear. Much swearing used to happen if you realised there was one hyperlink or something in colour in your otherwise black and white document that you'd not spotted before clicking print, and you heard the carousel with the toner cartridges on moving out of the home position as you stood up from your desk to go get your document...

So continues my quest to eliminate all the consumer grade tat from our IT infrastructure in this house. I was glad to find the 4600dn specifically because it's a model that I've prior experience both using and looking after, so I know it's built like a brick outhouse and is easy to look after. Must be one of the last generation before HP's kit really went down the pan.

I'd *like* one of the original LaserJet battleships...but just because I love kit like that rather than because I actually have a use for one. I really need colour, and having had a printer with a duplexer I'd miss it going back to one without.

I do have a LaserJet 1100 here though, which used to be my "general purpose I want to print manuals etc" choice before I got the ability to print two sided. Given it proudly proclaims MS-DOS comparability on the self test page it must be pretty old...That thing (and the one toner cartridge I bought for it) will probably outlast the human race. It's a real crying shame that in the mid 00s that HP's kit went off a cliff as they used to be so utterly dependable.

I might well see if I can sell the Epson on. It's a really good little printer by modern consumer standards, IF you're a regular user. I just don't use it often enough to keep it happy it seems. To be honest given the fact it's one of the models with the bulk ink tank system (I've had to top it up once in 1500 pages and about two years) if you can find ten minutes to print off a couple of photos a week to keep the heads happy it's not going to cost anything in ink. That's all it probably needs done.

The other gripe I have with it is that the Linux comparability with it is *mostly* okay, but every now and then the scanner drivers decide to fall over and require me to recompile them for no readily explicable reason. It only takes five minutes, but it's still annoying... especially when you just want to quickly scan something for someone. Between it's tendency to be cranky if left idle for longer periods and flaky drivers...nope, time to switch to enterprise grade gear with proper official Linux driver and software support please.

Honestly not sure what it's worth, know I paid the best part of £300 for it about two years ago... probably about £20 given the rate consumer tech depreciates at! If anyone on here wants it I'm sure we can arrange something.

Looking forward to getting the new old HP set up. NOT looking forward to carrying it upstairs mind you, they weigh something like 45kg as I recall!