CX AC query and request
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  1. #1
    Too many posts! JohnW's Avatar
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    Default CX AC query and request

    Happy New Year to CX folk, and others of course.

    I've just had the CX AC overhauled, with a new compressor and condenser, and receiver/drier.

    However, we can't get the single belt drive to the compressor 100% squeal-free without ridiculous belt tension - and it is of course the water pump bearings taking that load on the end of an extended shaft!!

    Does anyone have ideas? It seems to me I need to get a twin belt pulley fabricated to match the compressor but there isn't really enough room for the twin belt tensioner I'd need with it. I could of course re-rout the top radiator hose upwards.



    I'm sure I want to drop the belt tension, that is for sure.

    The upgraded AC is just freezing, which is great.

    Anyone interested in a batch of athermic windscreens..... We've been here before.

    Cheers

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    JohnW

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    Hi John,

    You have probably tried this already, but if not, how about a spray on belt grip product?

    Put me on the list for an athermic CX windscreen or two .

    Cheers,
    Andrew
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    COL
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    The only thing that I can think of is the belt new? and if it is, is it the correct belt? what I mean the right section.
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    I would check:

    -belt alignment
    -look for a collapsed bearing or something inducing a high load.
    -as mentioned belt section.

    Belt grip can work well but does damage the rubber - in my view this solves a symptom not the cause.

    Alex

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    Quote Originally Posted by andrewj View Post
    Hi John,

    You have probably tried this already, but if not, how about a spray on belt grip product?

    Put me on the list for an athermic CX windscreen or two .

    Cheers,
    Andrew
    Thanks Andrew. I'd forgotten 'belt dressing' products but the AC guy suggested it. I've just applied the spray, after discussions here in Perth this morning after I posted. CRC have a Belt Grip product, to be found for $20 in Super Cheap by the belts. It certainly is grippy. I'll report results in a few days. My fitting is non-standard (previous owner) but the belt is correct length and section, and OK. I could tighten it more, but right at the end of the water pump shaft seems such a bad idea!

    Cheers
    JohnW

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    Quote Originally Posted by Arekisir View Post
    I would check:

    -belt alignment
    -look for a collapsed bearing or something inducing a high load.
    -as mentioned belt section.

    Belt grip can work well but does damage the rubber - in my view this solves a symptom not the cause.

    Alex
    Thanks Alex - thoughts appreciated. I totally agree re symptom not cause! The cause is engineering an AC compressor off the end of an extended water pump shaft!!! My feeling is that a twin belt pulley to reduce the forces on that shaft, i.e. avoiding overloading the water pump bearings, is the best solution available, as I can't put the AC compressor anywhere else without major engineering. I guess I could look into a toothed belt system, but I've just paid for a new vee belt compressor. Isn't hindsight great?

    Alignment was perfect, probably a credit to the previous owner. It is now perhaps 1-2 mm off but just acceptable in my judgement. It's something to fix with a small spacer sometime.

    The AC has worked for 37 years without destroying water pumps as far as I can see, but new compressor, fully gassed etc might just have increased the torque requirements, only on startup I'd add, just over the friction bite.
    JohnW

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    Wider belt if it is currently bottoming out on either the drive or driven pulley.
    What portion of each pulley is in contact with the belt? Does it wrap around nearly 180 degrees or is it just touching one edge?
    You could possibly get a different tensioner that works on the back of the belt to increase the contact areas. I don't know of that's a great idea with a v-belt though.
    I know it's new, but is there excessive resistance in the compressor?
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    Hi David and thanks.

    The old compressor had the same problem - minor slippage when kicking in from idle. There is less than 180 degrees 'wrap around' on the drive pulley but it runs fine in steady state. If I recall correctly, the previous owner manufactured a largee diameter drive pulley to increase the speed of the compressor. Driven off the camshaft, the compressor DRIVE pulley spins at half engine speed, so runs typically at 1,000 to 1,500 rpm, the compressor being fine about 2,000 rpm. (The compressor is rated to 8,000 rpm, but that's 16,000 rpm at the engine and it is NOT a V-16 BRM!!)

    I'm inclined to reduce the drive pulley diameter a wee bit, to standard, and go with two belts, as the new compressor has two belt grooves, as is did the original one. Since the AC is so good with the new gear, a wee bit of reduction in speed but a better mechanical advantage by means of a smaller drive diameter, makes sense to me. My main concern is water pump bearings, as you'd have picked up.

    Working out how to fit a wider tensioner pulley is an issue, as its wider diameter will foul the horizontal curve of the top radiator hose where it leaves the header tank if I leave it standard.

    I'll see how I go with the belt sticky spray, but agree with Alex that it addresses the symptom, not the cause.

    Cheers
    JohnW

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    If you are intending to fabricate a double pulley system. I'd choose a single poly vee belt drive system everytime.

    Clutches and pulleys are often compatible between the same brand compressors . And most modern cars use poly vee to drive aircon compressors, so you should be spoilt for choice for parts from DIY wreckers.

    The belt is more compact than Dual A section and you have no issues matching belts.

    And poly vee transmits power with less wrap than Vee belts.
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    Quote Originally Posted by robmac View Post
    If you are intending to fabricate a double pulley system. I'd choose a single poly vee belt drive system everytime. Clutches and pulleys are often compatible between the same brand compressors . And most modern cars use poly vee to drive aircon compressors, so you should be spoilt for choice for parts from DIY wreckers. The belt is more compact than Dual A section and you have no issues matching belts. And poly vee transmits power with less wrap than Vee belts.
    Thanks for that. Do you mean the standard "modern" type of broad, flat accessory belt such as our Xantia and Renault Scenics have? If so, I hadn't thought of that. It would allow me a tensioner from the back side too, eliminating the geometry issue with the top radiator hose.

    Less 'wrap' is one thing and good, but what I really need is less tension, to reduce forces on the drive belt hence on the water pump bearings. I imagine I'd achieve both??

    Back to the drawing board with the potential modification!

    This just shows the benefit of posting on Aussiefrogs - the ideas flow!

    Happy New Year to you and yours.
    JohnW

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    You should be able to find plenty of donor pulley options for multi V belts if you wanted to go that way. 5 or 6 rows is common. They work well with the tensioner on the back of the belt, which should increase the contact area at the compressor. A walk around a junkyard should yield what you need, but choose something common with a cheap and easy to get tensioner / roller set. You can even add a secondary roller if you are feeling really keen.

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    UFO
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    Is the belt 10mm or 11mm wide? The pulleys are engineered for 10mm.
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    Quote Originally Posted by David S View Post
    You should be able to find plenty of donor pulley options for multi V belts if you wanted to go that way. 5 or 6 rows is common. They work well with the tensioner on the back of the belt, which should increase the contact area at the compressor. A walk around a junkyard should yield what you need, but choose something common with a cheap and easy to get tensioner / roller set. You can even add a secondary roller if you are feeling really keen.
    Naismith engineering, in Fairfield carry a huge range of pulleys and belts, if you can't find what you need.
    http://www.naismith.com.au/upload_pd...53122a7adb.pdf
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    Quote Originally Posted by UFO View Post
    Is the belt 10mm or 11mm wide? The pulleys are engineered for 10mm.
    Blow me down. The alternator and HP pump belts are 10 mm. The AC belt is 11.5 mm. I'd never noticed and it has always been on the verge of squealing.

    Thank you!! Next job, 10mm belt!!!!
    JohnW

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    Contact Optibelt, I think they are in Dandenong, Vic. 03 8791 2700. They know all about belts and supply really top quality belts.

    I have a poorly engineered, Australian made, ride on mower. It is an AMC, made in Horsham, company went broke about 10 years ago. They use a friction drive transmission, like a Greenfield but not as good. One of the transmission belts has a horrible life, folding back on itself and twisting 90 degrees, wraps around a small diameter pulley at one end (about 50% coverage) and around two huge aluminium discs that run really hot at the other end.

    When the mower was new, I had a lot of trouble with belt slipping and phoned the manufacturer to grumble. He acknowledged it was a known problem and said they were working with several belt manufacturers to come up with one that was up to the task. The eventual answer was a "black Optibelt."
    It is a SPA series belt, I think that stands for Special Purpose A section belt, though it is fractionally fatter than an standard A section belt. It is amazingly grippy, it just doesn't want to slip. Mine are labelled "Optibelt SK" in white, they are colour coded to suit various applications.

    I have tried other brands of SPA-section belts but none are half as grippy as the Optibelt.

    Funny thing is, this mower has two belts of the same size, the transmission belt and the cutter belt. The cutter is engaged / disengaged by a tensioner being applied or released. For smooth engagement it requires a belt that can slip a bit, they have a cloth wrapping and are called a "clutching belt." It recently broke and I didn't have a spare clutching belt, but had a spare transmission belt, the Optibelt. So I fitted that. It is hopeless at clutching - it bites hard and fast when you engage the lever (Squawks loudly when it bites) and won't release drive when I release the clutch lever - the belt is so grippy it just keeps on driving. (Quite dangerous in that situation.) It is interesting that a change of brand makes such a difference to the belt.

    In your situation I'd try an Optibelt before exploring other options.

    Having said that, the idea of a poly-vee belt (the standard "flat" belt used in all modern cars) is a good idea if you can find suitable pulleys.


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    Quote Originally Posted by simca1100 View Post
    Contact Optibelt, I think they are in Dandenong, Vic. 03 8791 2700. They know all about belts and supply really top quality belts.
    That is such useful information! Many thanks and good to see your name again on the forum.

    Best wishes,
    JohnW

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    http://www.accentbearings.com/pdf/op...ct_catalog.pdf

    Link to Optibelt catalogue. Wow. Thanks.
    JohnW

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    Well, it seems to be behaving with a wee spray of CRC Belt Grip, so that belt was just on the point of gripping.

    It looks to be as if the AC belt pulleys are 12 mm (about 1/2") to correspond with the Sanden compressor, and measure up a couple of mm wider than the alternator and hydraulic pump pulleys.

    Yes, I can see that very slight misalignment of the idler pulley - need to shim out the drive pulley about 1 mm.

    We'll see how it goes. I have very little latitude with the tensioner position, given the geometry of the setup. I reckon the easiest approach to achieve less tightness at the end of the water pump shaft will be to set up a double V-belt drive pulley of the original (smaller) diameter, improving the 'gearing' and accepting slightly lower compressor revs. Slightly lower revs are not going to matter since the system now works so well, although I can see why the previous owner would have made that change 12-15 years ago.

    Does anyone have any spare pulleys?

    I agree the multigroove approach has a lot going for it, but I'll start with the simpler, double-vee given I've just paid for a new compressor with the V-belt drive.

    All comments very much appreciated. I've discovered a bewildering array of v-belts, that is for sure. Must ring the blokes in Victoria on Monday and have a chat.

    Cheers
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    JohnW

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    Hi John,

    Having a bit of a flashback :-) As youíve said, the pulley was larger to spin the air con compressor a bit faster - I think I still have the tin of CRC belt grip in the garage... I used this on an earlier CX I had too on the compressor. The whole arrangement for driving compressor/alternator isnít the best... almost needs a support bearing mounted off the compressor top mounting lugs! The larger pulley was sourced locally but from where I canít remember. This was in the day of poring over catalogues and making phone calls - the interweb makes it easier now.... Is the new compressor a 507? Intrigued by the change of condenser - do you know how it differs? the previous one was chosen based on maximizing surface area within the space available.





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    I nearly sent you a PM!! Good you noticed.

    Yes, the engineering isn't the best, thinking of leverage on the two water pump bearings! Yes, a support bearing would be a really good idea but, like the R16 factory arrangement off the end of the camshaft, it was very much post-development engineering.

    The new compressor is SWJ1-508. Autocool (in East Perth, Lord Street) really know their stuff and sorted an SM recently. Their comment is that the new design condensers are much more efficient and I suspect it is in airflow, as the engine is now running cooler, even with the AC switched on! It's a cooler AC blast than when I bought it, to the extent I can remember of course, as there's the 'wishful thinking' factor!

    On balance, I'm sure two belts would be an improvement, even if it means having a double pulley machined and the top radiator hose re-routed with a made up system to allow for a wider tensioning pulley system. As usual, robmac is on the money, as a multi-v belt would be best.

    The best compromise might be too difficult: both of the double drive pulleys adjustable by shims in the vee so that the tensioning pulley is redundant AND the wrap-around improved.

    It has an electric fuel pump too, a great step forward for intermittent use. The C-matic is behaving perfectly and I found a new electrovalve some years ago. It sits in its box.....

    Best wishes
    JohnW

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    Real cars have hydraulics DoubleChevron's Avatar
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    That one actually looks pretty good. I bet its the twin belts slipping and squealing ... Not the super tight A/C belt. You need to run everything incredibly tight ... water pump destroying tight, or it'll just slip and squeal. This is "normal" CX. All of the factory setups do it too. The CX water pumps seem to die as a past time. I think the issue is the very short belt runs. The longer the belt run, the less tension required.

    seeya,
    Shane L.
    PS: The twin belts... I bet they are the ones slipping and squealing them .... they need to be TIGHT! especially with the added alternator load of running the AC
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    I agree with Shane as I just fitted a new compressor & experienced the squealing due to the twin water pump belts & not the compressorís. Btw how much r134a gas did your AC tech add? (Dual AC)
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    Probably too late for this, but changing the refrigerant from R134 to HC12 would help. HC12 (propane isobutane) is a much more efficient refrigerant, which means it operates at significantly lower condenser pressure. Lower condenser pressure = lower torque required at the compressor = lower belt tension required...
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    Quote Originally Posted by citroenthusiast View Post
    Probably too late for this, but changing the refrigerant from R134 to HC12 would help. HC12 (propane isobutane) is a much more efficient refrigerant, which means it operates at significantly lower condenser pressure. Lower condenser pressure = lower torque required at the compressor = lower belt tension required...
    They still slip. The belt run in the CX is TINY. They are really, really little belts. They need to be tight as a drum. The CX compressor load is large. Even with propane (Hychill -30 out here), and both radiator fans running full bore, the high side pressures can get impressively high!

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    Quote Originally Posted by citroenthusiast View Post
    Probably too late for this, but changing the refrigerant from R134 to HC12 would help. HC12 (propane isobutane) is a much more efficient refrigerant, which means it operates at significantly lower condenser pressure. Lower condenser pressure = lower torque required at the compressor = lower belt tension required...
    Thanks for that thought. Yet another variable to play with! The AC company I used just finished sorting out an SM very nicely. I've enjoyed your SM posts over the years too, so double thanks!

    Regards
    JohnW

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