TfW 158s air conditioning problems

[Andrew888]

Here we go again.

The majority of Transport for Wales services between Shrewsbury and Birmingham will be cancelled on Sunday 2 August and Monday 3 August.

We’re unable to run our older trains during periods of high temperatures due to on-going failures with the air conditioning systems of our legacy fleet. We are working with our supply chain to resolve this as soon as possible before our older trains are replaced as part of our £800m investment in brand new trains.

Please note - The final three services between Shrewsbury and Birmingham on Sunday will run as planned.

(TFW no longer provide journeycheck so I can't provide a specific link to the update.)

The forecast temperatures for those two days in that area are 24° and 27°. Clearly a heatwave worth adding 1-2 hours per trip east of Shrewsbury and running rammed 2-carriage trains for.

It just seems utterly mad. (Though happily in this case I can delay my journey until Tuesday.) Again, the A/C has almost never worked (discernibly at least) before on this line.

 

[Cardiff123]

Here we go again.



(TFW no longer provide journeycheck so I can't provide a specific link to the update.)

The forecast temperatures for those two days in that area are 24° and 27°. Clearly a heatwave worth adding 1-2 hours per trip east of Shrewsbury and running rammed 2-carriage trains for.

It just seems utterly mad. (Though happily in this case I can delay my journey until Tuesday.) Again, the A/C has almost never worked (discernibly at least) before on this line.

Here's a link on the TfW website.

Disruption and service changes | Transport for Wales

Transport for Wales | Buy Cheap Train Tickets and Check Train Times

tfw.wales

Of course, TfW will be running even older trains than 158s long term with 153s and Mk 4s, but the 153s have opening windows and Mk 4 air con actually works.

 

[Peter Sarf]

Here we go again.



(TFW no longer provide journeycheck so I can't provide a specific link to the update.)

The forecast temperatures for those two days in that area are 24° and 27°. Clearly a heatwave worth adding 1-2 hours per trip east of Shrewsbury and running rammed 2-carriage trains for.

It just seems utterly mad. (Though happily in this case I can delay my journey until Tuesday.) Again, the A/C has almost never worked (discernibly at least) before on this line.

My bold. Oh the irony. Those temperatures are good enough to drive plenty of people out of their homes to go on leisure travel. So a lot of extra demand and so revenue to be had. But a good ten degrees below what we in the South East have been enduring and TfW throw in the towel. I know South Wales has already been hotter than 27 degrees C.

Last year I bought my first car that has air-conditioning. But it still has opening windows.

I would never buy a car that did not have opening windows so who's idea was it have 158s with no opening windows - even if locked shut ?.

 

[skyhigh]

I would never buy a car that did not have opening windows so who's idea was it have 158s with no opening windows - even if locked shut ?.

A 158 does have some opening windows.

 

[Russel]

Here we go again.



(TFW no longer provide journeycheck so I can't provide a specific link to the update.)

The forecast temperatures for those two days in that area are 24° and 27°. Clearly a heatwave worth adding 1-2 hours per trip east of Shrewsbury and running rammed 2-carriage trains for.

It just seems utterly mad. (Though happily in this case I can delay my journey until Tuesday.) Again, the A/C has almost never worked (discernibly at least) before on this line.

This is just unacceptable, not only is the current heat not extreme, it hasn't been for a couple of weeks and TFW/ATW have been happy to run 158s in hotter temperatures with no AC for 20+ years...

 

[M60lad]

Other operators will still be operating their 158s with working or not working AC so what's the reason why TfW are throwing the towel at the slightest temperature increase?

 

[Cardiff123]

Other operators will still be operating their 158s with working or not working AC so what's the reason why TfW are throwing the towel at the slightest temperature increase?

This seems to be the reason:

25 degrees is not extreme, but it's recently been 33-35 degrees.
As the 158's have aircon fitted, Depots are obliged under maintenance rules to not allow units to leave the Depot with aircon not working. It also takes into account Driver Cab air con.
Carriages have been reaching 35-40 degrees inside. Try driving a train in that temperature. Drivers are (quite rightly) refusing to drive in those conditions, and guards are (quite rightly) refusing to allow passengers to put in those conditions.

 

[MrC]

Engine power isn't the issue it's the alternator supplying the electrical side that possibly needs uprating. This will put a larger parasitic load on the engine leaving less available for traction but the amounts we are talking about here are miniscule and doubt it would be noticed or affect train schedules. Not like a class 31/4, which was reputed to be able to heat more coaches than it could haul!!!

Bear in mind that the 158/159 alternators are hydraulically driven and sized to fit in the available space under the sole bar so it may not be as simple as just fitting a "bigger" alternator. You may have to look at uprating the hydraulic pumps, pipework, cooling, etc, and some of the hardware will not be off-the-shelf fitments. Quite possibly feasible but perhaps not as simple or as economically justifiable as it first looks.

Edit: you'd also have to examine the existing cabling to see if it can carry the additional load at full demand. Again feasible but it all adds up.

 

[Harpo]

Bear in mind that the 158/159 alternators are hydraulically driven and sized to fit in the available space under the sole bar so it may not be as simple as just fitting a "bigger" alternator. You may have to look at uprating the hydraulic pumps, pipework, cooling, etc, and some of the hardware will not be off-the-shelf fitments. Quite possibly feasible but perhaps not as simple or as economically justifiable as it first looks.

I’ve always assumed that this was why the 158s had (electrical) power-shedding mods to create the spare power needed for ETCS.

 

[bunnahabhain]

One thing that may also be worth investigating is when the last time the condenser coils were cleaned. There's a suggestion that they've never been done at EMR and one unit has recently had them done as a test to see if it improves the efficacy and reliability of the cooling.

 

[MrC]

I’ve always assumed that this was why the 158s had (electrical) power-shedding mods to create the spare power needed for ETCS.

Heh. Savvy 158/159 SWT/SWR drivers often used to turn off the saloon lights before starting the engines to avoid the (ISTR) alternator excitation mcb tripping out. Probably not so much of a problem these days with LED lighting but it did show how borderline the old designs were so I expect there's been much head-scratching required to retro-fit ETCS.

 

[Snow1964]

Here's a link on the TfW website.

Disruption and service changes | Transport for Wales

Transport for Wales | Buy Cheap Train Tickets and Check Train Times

tfw.wales

Of course, TfW will be running even older trains than 158s long term with 153s and Mk 4s, but the 153s have opening windows and Mk 4 air con actually works.

Of course, the hotter summer months of July and August tend to happen about every 12 months, so not some unexpected freak event.

Earlier in year they knew summer was coming, and had a simple choice, fix a/c on 158s, or make effort to get 197s in service by time hotter summer weather seasonally occurs

It appears they took a third option, do neither.
Perhaps the question should be why did they not prepare

 

[Cardiff123]

Of course, the hotter summer months of July and August tend to happen about every 12 months, so not some unexpected freak event.

Earlier in year they knew summer was coming, and had a simple choice, fix a/c on 158s, or make effort to get 197s in service by time hotter summer weather seasonally occurs

It appears they took a third option, do neither.
Perhaps the question should be why did they not prepare

I think this puts to bed any idea that TfW will keep 158s any longer than needed to cover a shortfall of other units, eg. In the south with 398s.
From the statement they released, TfW obviously want rid of the 158s ASAP and tbh I can't see them spending any money on fixing the air con now.

 

[Andrew888]

Maybe it only became apparent to management that the A/C was broken after the heatwaves earlier this year? I took a trip during the third heatwave where it was 33 outside and likely ~40 inside on the Shrewsbury/Mach section. But that would only make cancelling trains now even more ridiculous, given they were happily running a full schedule then. And it's the BHI/SHR section they're cancelling anyway.

There seems to be a basic lack of common sense here.

It's also pretty damning if that lack of realisation is indeed the case. (But having read the Talerddig reports... \o/.)

I do wish they'd improve their comms too. There's nothing on the front page or their service updates page about this, and the live map which has replaced more useful textual information shows no incident on that line today. You can find something if you do Live Times > Travelling Today > Disruption and Service Changes, but not the more usual Live Times > All(!) Updates.

(I only intuited to search for some incident after finding the national rail route finder wasn't giving me expected results, instead routing me via Crewe. As above, I really do miss journeycheck. It was a one-stop shop for quickly finding out exactly what was going on on the TFW network.)

I know the 158s are supposedly being replaced with newer 197s later this year, but we've been told that for 7+ years now, so I'll believe it when I physically step on board a Shrewsbury/Aber departure . (I guess there must be a shortage of those too though, given they at least sometimes run the BHI/SHR portion on a 197 and then switch people to an ETCS 158.)

== Doublepost prevention - post automatically merged: 3 Aug 2026 ==

On a Cambrian 158 from Shrewsbury now. No A/C. But! Four carriages (just as well given the crowd, but I was expecting the worst) and the windows have been opened, so it's fine. Temperature 27°.

 

[Russel]

Maybe it only became apparent to management that the A/C was broken after the heatwaves earlier this year?

If they have only just noticed something that has been broken for 20+ years, is broken, then there is much bigger issues than that need dealing with.

 

[Ribbleman]

Is it not the case that TfW will be required to return the 158s to Angel Trains with all equipment in full working order, including the air conditioning? Unless they agree to foot the bill for Angel making arrangements to have the necessary work carried out by a third party?

 

[robert thomas]

Modern Railways reported that SNCF has made widespread cancellations due to Corail stock being unable to cope with their high temperatures (admiiedly up to 40 degrees)

 

[3RDGEN]

Is it not the case that TfW will be required to return the 158s to Angel Trains with all equipment in full working order, including the air conditioning? Unless they agree to foot the bill for Angel making arrangements to have the necessary work carried out by a third party?

The Air Con will be working on it's return, however it will not be 30+ ambient with 70 passengers in the saloon when that happens. The Air Con on 158's isn't going to work in the recent temperatures, it never has from build hence why they had emergency windows fitted from build and why the 159's had more fitted. The newer system is better but your still limited by the power supply and space on the units, just compare the air con units on CL175, 185, 19x or 390 units to those fitted above the vestibule areas on the 158's.

 

[MrC]

Modern Railways reported that SNCF has made widespread cancellations due to Corail stock being unable to cope with their high temperatures (admiiedly up to 40 degrees)

SNCF withdrew the older stock in advance as they knew that the A/C wasn't designed for extended periods of temperatures that ended up exceeding 40C in the shade in many places. Turned out to be a wise decision - they also pushed the "do not travel" message very hard in advance so the withdrawal of the older stock wasn't so critical.

 

[Cardiff123]

I'm surprised that TfW have not announced yet that their 158 fleet will be grounded over the next few days due to the extreme forecast temperatures of around 30C right across mid and north Wales, higher along the borders in England. Maybe the air con has been fixed?

 

[BuhSnarf]

Is the issues with the 158 Air Con not the fact that the system / compressors etc that it has was designed to work with CFC type gas which is obviously no longer allowed. The CFC free gas needs a more powerful system to achieve the same cooling power. This is why when the temperature outside is hot the system struggles and then eventually overheats and trips.

I say this as someone who works in an office where the exact same thing happens.

Therefore, the only fix would be to completely rip out the system and install a newer one which I am fairly sure would be incredibly costly.

 

[Bletchleyite]

I don't remember where I read it but that was what I read about it, and it would tally with 158s having been like walking into a fridge on a hot day when I was much younger (unlike e.g. Mk2 and Mk3 stock, which was always rubbish).

 

[skyhigh]

Is the issues with the 158 Air Con not the fact that the system / compressors etc that it has was designed to work with CFC type gas which is obviously no longer allowed. The CFC free gas needs a more powerful system to achieve the same cooling power. This is why when the temperature outside is hot the system struggles and then eventually overheats and trips.

I don't remember where I read it but that was what I read about it, and it would tally with 158s having been like walking into a fridge on a hot day when I was much younger (unlike e.g. Mk2 and Mk3 stock, which was always rubbish).

I'm pretty sure that's just an urban myth - for a start, most (if not all?) 158s have been fitted with upgraded air con that was designed for the new gas.

A newly overhauled unit is still cool inside.

The main issue is that there are long pipe runs from the underframe to the roof mounted units, which are a nightmare for pinhole leaks with the flex of the body and difficult to locate/repair.

The aircon is also often repaired and maintained by outside contractors which incurs a call out fee, so depots won't do so unless there's an obvious fault. They will just reset, do a test and if it's within spec (even barely) will just let it run.

The system is pretty low power so the usual problem is it gets overwhelmed, particularly if it's not working at full capacity, and can't keep up. Obviously when they were new everything was working properly.

Quite often a unit that's not at peak performance will work fine at the start of the day and continue to maintain a reasonable temperature but if it's left with engines off and doors open for any length of time then once it's started back up it will never be able to cool back down again.

 

[Russel]

I'm surprised that TfW have not announced yet that their 158 fleet will be grounded over the next few days due to the extreme forecast temperatures of around 30C right across mid and north Wales, higher along the borders in England. Maybe the air con has been fixed?

Why announce it now when you can leave it until the very last minute just to really wind people up...

 

[Cardiff123]

Why announce it now when you can leave it until the very last minute just to really wind people up...

Announced this afternoon
https://tfw.wales/service-status/disruption-and-service-changes

Disruption between Shrewsbury and Birmingham on Wednesday 12 and Thursday 13 August
The majority of Transport for Wales services between Shrewsbury and Birmingham will be cancelled on Wednesday 12 and Thursday 13 August.

We’re unable to run our older trains during periods of high temperatures due to on-going failures with the air conditioning systems of our legacy fleet.

We are working with our supply chain to resolve this as soon as possible before our older trains are replaced as part of our £800m investment in brand new trains.

Please note - The final service between Shrewsbury and Birmingham will run as planned.

Ticket acceptance has been agreed with West Midlands Railway for journeys between Shrewsbury and Birmingham.

We apologise for any inconvenience caused by this disruption

 

[Andrew888]

Yes, buried as usual (you kind of have to know that page is there), I only found the announcement after my wife mentioned she'd seen something on facebook.

"We are working with our supply chain to resolve this as soon as possible before our older trains are replaced as part of our £800m investment in brand new trains."

Hmm. Well, which is it. Repair or wait for the 197s? (And, new rule, no more talking about the new trains. They'll be old trains by the time we see them in ETCS world.)

I have a lot more tolerance this time around because it's going to be 31° and 33° in Shrewsbury, versus the 24°C last time. If they would just publish a firm guideline -- we're not running these trains if it's 30°+ for instance -- it would help with planning.

Also, I'm sure I've travelled on 197s BHI->SHR before, and then done the usual swap dance at Shrewsbury. (Including that one where the ongoing train is on platform 3, so you get to go down the two flights of stairs, through the barriers, outside to the car park, and then back up the external stairs to the top.) I wonder why that's not an option now. If it's a shortage of 197s, that doesn't bode well. Or are the 197s having A/C issues too?

I'm travelling on Friday when it's due to be... 24°C. I wonder what my odds are

 

[Recessio]

Is the issues with the 158 Air Con not the fact that the system / compressors etc that it has was designed to work with CFC type gas which is obviously no longer allowed. The CFC free gas needs a more powerful system to achieve the same cooling power. This is why when the temperature outside is hot the system struggles and then eventually overheats and trips.

I say this as someone who works in an office where the exact same thing happens.

Therefore, the only fix would be to completely rip out the system and install a newer one which I am fairly sure would be incredibly costly.

It's not that simple - you don't just regas an old R12 system with new gas. It has to be adapted anyway because of different pressures and oils and the requirements for even tighter seals. They would not have simply just pumped new gas into the existing units unmodified.

That said, it doesn't negate your point that clearly these systems are either inadequately specced or inadequately maintained, and perhaps the best solution is to rip them out and install new ones.

 

[Andrew888]

The aircon is also often repaired and maintained by outside contractors which incurs a call out fee, so depots won't do so unless there's an obvious fault. They will just reset, do a test and if it's within spec (even barely) will just let it run.

The system is pretty low power so the usual problem is it gets overwhelmed, particularly if it's not working at full capacity, and can't keep up. Obviously when they were new everything was working properly.

Quite often a unit that's not at peak performance will work fine at the start of the day and continue to maintain a reasonable temperature but if it's left with engines off and doors open for any length of time then once it's started back up it will never be able to cool back down again.

Very interesting, thanks for the info. I suspect my "has almost never worked" experience is due to some combination of this. Traditionally in summer the trains are crowded due to holiday traffic which can't help.

I think I said elsewhere that I have experienced working A/C on these trains twice (in over a decade). Both times this was one sole car in a four-car set. It did make a really noticeable difference -- it was well worth moving to that car, even though all the others having their windows wide open must have had an impact. So I guess we know they are _theoretically_ capable of of cool running.

(I still don't understand why they all need to be fixed right now, when they're supposedly gone post-summer. 2025 had quite a few 30+ stretches too.)

 

[Bletchleyite]

That doesn't read like the fleet being grounded as that would mean no service west of Shrewsbury?

 

[Russel]

That doesn't read like the fleet being grounded as that would mean no service west of Shrewsbury?

Could it be they only have enough sets with working air-con to operate services west of Shrewsbury?