Zulu10

That's an interesting point, but wouldn't that just cause the ECU to jump between the 'no load' idle speed of 950 rpm and the 'AC on' idle speed of 1050rpm? Whereas in this case it's going right up to 1500 to 2500, and sometimes 3,000 rpm.

Can anyone on here think of a possible cause of this aberrant behaviour on a 1997 Esprit GT3 with Delco fuel injection, please: When the air conditioning is switched off, the car behaves impeccably, and idle is sweet and stable. However, when the air conditioning is switched on, the idle speed will rise, inconsistently to somewhere between 1500 and 3000 rpm. Very occasionally this will be accompanied by a 'Check Engine' amber caption which clears within seconds. Ordinarily, for an idle speed problem I would be looking at the IACV and for air leaks. However, prior to recognising that the problem only occurs when the air con is running, I had already bought a new IACV, and it made no difference. Regarding air leaks: when the rubber pipe feeding the IACV is artificially compressed, then the engine can be brought almost to the point of stalling, so that suggests that the IACV is pretty much the only source of intake air. So those two facts suggest to me that the idle system is doing what it should, and indeed it does whilst the air con is off. The air con is such a simple system that interacts with the ECU by requesting compressor on, in response to which the ECU pulls in the relay that provides power to the compressor clutch, that I can’t see how a problem can occur. Interestingly though, once air con is switched off, any attempt to restart it is ignored and only actioned once the ignition is cycled through off. So, what can the air con do to affect the idle? My shortlist is: EMC/RFI – could the air con clutch generate interference? Direct electrical cross feed due to wiring loom problem? Unlikely because car has only done 21,000 miles and in general the loom seems to be in excellent condition. Vacuum pipes? How can a loss of vacuum, for example at the dashboard, adversely affect the engine idle on an engine whose only vacuum control is of the wastegate? ECU Problem? Could the code somehow be corrupted such that the ECU behaves erratically? Bad earth causing loss of reference voltage. But the IACV and throttle pot are both connected directly to the ECU from which they receive their reference, so that seems unlikely. Does anyone else have any other theories, please?

Hi Trevor, I’ve got a 1997 GT3, which is an early dash model, and is a bit of a garage queen having only done 21,000 miles. It’s not for sale, but if you’d like to come and clamber all over it then you’d be very welcome. There are two downsides: 1) is that I am in north west Hampshire, and; 2) the car is now SORNed for winter.

From memory I had a pile of the twenty or so front components in a box - I took them down to Poole to drop so that I could be nosey, and they dropped them off ten days later and the cost was less than £100.

Gentlemen, Are you really sure that powder coating suspension components is a good idea? The risk is that if a small stone hits and microscopically penetrates the coating, then moisture will creep in. The consequence of that is that the corrosion will occur beneath the powder coating, an an insidious way where it can be neither seen nor cured. Worse is the fact that the ensuing corrosion will simply creep along and spread under the coating. The outcome of this is really quite frightening when an apparently perfect component suddenly fails . The alternative approach is to have all the suspension components blasted and then re-plated as per original. Yes the plating can be penetrated, but if that happens then the consequent corrosion can be seen and dealt with. The cost is quite reasonable and there’s a company in Poole, Dorset who I use who will collect, process and drop off – Dorsetware www.dorsetware.com – but I suggest that it’s best to call them on 01202 677939 because they’ll talk you through the options and usually ‘do a deal’. I should add that I have no connection with them other than being a many time customer. As an alternative, this is a quote from a Pistonheads discussion this week: "You should try Mercury Electroplaters in Camberley, I kept on popping down there to get the parts for my V12 engine zinc plated, they did a great job and even chrome plated my rusty headlamp surrounds. They matched the Jag OEM zinc finish Unit 7H, Bridge Trading Estate, GU15 2QR"

A further update: I've just received a Four Seasons 33403 for my 1997 GT3, and as expected it fits perfectly. I bought mine from Topspeed Automotive (www.topspeedautomotive.com) who from what I can gather are a U.S. based parts distributor with a UK outlet. Unfortunately inflation and a weak Pound means that the price delivered to UK is now £36.95. The part is here if anyone needs it: https://www.topspeedautomotive.com/ac-receiver-drier/79966-steel-filter-drier.html

Updated version with partially threaded mounting studs and fillets around internal right angle corners:

You were right: learning a new CAD package is v. hard work! However, I'm pleased with the result. Just need to talk to a 3D printing house in the morning... Have now found a print bureau in Portsmouth who have an on-line quoting system that suggests £10 or so (presumably plus VAT) per unit, plus a small set up fee.

You're right there's some work involved. I'm waiting on a quote for the scanning and reverse engineering into a CAD file. Alternatively, I keep threatening to learn how to use a CAD package properly, so this might be the ideal opportunity to simply draw the casing shape from scratch. There are many of the intricacies of the Caerbont casing that do not seem relevant to our gauges, so they could be omitted, whilst taking the opportunity to slightly thicken the plastic case. Then of course I'd have the ideal excuse to buy a 3D printer... 😉 On reflection, I could also update the mounting to use a finely threaded external collar, rather than the metal bracket.

Thanks for the confirmation. I agree with the issue of originality of the front of the gauges, but am less concerned about the casing since it can't be seen with the gauges in situ. Hence my desire to reverse engineer the shape and then increase the thickness of the casings to add strength.

Yes, they are the Caerbont instruments, whose co-located sister company, Speedy Cables, can apparently repair them, but there are three disadvantages to this: The company's name is a bit of a misnomer in the sense that my and many others' experience with them is that they are anything but speedy. Second is that I'm told that they charge upwards of £50 to repair each gauge, and third is the fact that I would still have delicate plastic casings.

Funnily enough that was my wife's suggestion - to replace plastic with metal - and I considered it, and also discussed it with an instrument repairer. Unfortunately we concluded that the way each of the terminals is brought out of the back of the gauge - using a threaded stud - would mean that there would be a lot of re-work necessary to make insulating pillars for each stud. I therefore discounted the idea for the time being. At one point I also considered buying cheap Chinese gauges from AliEpress and cannibalising them just for their casings...

Thanks Colin, but if you search this forum, other Lotus groups, and indeed any number of TVR forums (fora?) you'll see that it's a commonly mentioned problem. I think that it's exacerbated by over-tightening of the knurled nuts that hold the mounting clamp. I've tried glue but would prefer something more permanent....

I've just realised that despite being a member for almost a decade, my car isn't on the list: 1997 GT3 in Calypso Red VIN: SCC082920VHA42141 now residing in Hampshire

Whilst concluding my conversion to LED lighting on Sunday I got a nasty shock when I removed the instrument binnacle cover and found that all five of my minor gauges are exhibiting some degree of cracking. The water temperature and fuel gauges being the worst; having cracks around more than 300 degrees of their circumference. All this on a car that has done 20,000 miles hence has spent most of its life away from extremes of temperature. The cost of replacement is obscene: £450 for five gauges, and I’m still awaiting ‘Speedy’ Cables’ quote for repair, but it occurred to me that either of these solutions will still leave me with the same weakness to future failure. I’m therefore contemplating a modern alternative which is to have a casing 3D scanned as a baseline, then converted into a CAD file which can be modified to thicken the plastic to strengthen where appropriate, before being manufactured using 3D printing. The non recurring expense of going for injection moulding rules it out unless there’s a demand for thousands, which I very much doubt, but I wonder what the potential interest might be for modified casings? I’m aware that the same gauges are used in the Esprit, early Elise and some TVRs (anything else?) so I can’t imagine that I need to make a batch of more than 10 sets i.e. 50 cases initially. Obviously I’d want to amortise my initial outlay in scanning and re-designing, but firstly I’d like to get a feeling for who would be interested, please? Hopefully this doesn’t count as illicit marketing… but happy to be corrected.