1hz intermittent a/c

[95CRUZA]

Hi guys, cant find that anyone else has posted re this problem yet!!. My 95 80 series 1hz a/c is working intermittently, ie will work for a few hours then blows uncooled air, left overnight will work again next day no probs. This now seems to be occurring more regularly. Recently had the fan unit replaced. Don't know when last re-gassed have had truck for a year now and everything is spot on. Has done about 260k now. Any ideas appreciated, have got it booked in to my local on 7th for checking, but it probably wont do it for them while they have it, you know what it's like!
cheers hope all had a happy new year.

[HDJ105]

Could be any number of things :(

Over / under charged, high or low pressure in system.
Blocked or inefficient condensor
Engine cooling system getting too warm and cutting a/c out to assist cooling.

[dieselpower]

Does it always do it while the truck is working hard? I know the 100 series has it, and I think the 80's do too - they have a safety mechanism built in that cuts the A/C when the engine temp rises to try to cut the load and hopefully reduce the temp in the engine.

I've heard of ex mines vehicles doing this particularly on long uphill stretches because of coal dust in the radiators. Perhaps that's a possibility, and worth checking? I would have thought that if it was the gas you'd know about it before the first couple of hours...

[95CRUZA]

Doesn't do it only when working hard, towed the camper to Innaminka in Sept, only needed it on to keep out dust and bit cooler than outside, light load (only the missus and me), and then the other day my missus drove 300kms (pretty hot though) so only her some clothes (????) and the fridge and did it on the way up and on the way back (another 300kms).
Temp gauge never moves.

[95CRUZA]

Thanks for those replies, have had it checked out, nothing found, will probably be getting radiator flushed and checked for any blockages and then see what happens.
Cheers again.

[steveandviv]

if the temp is not moving in the truck then it's not the radiator that's for sure. I had to fill up on a mud pudle once after breaking a hose in the bush. I flushed the radiator many times but it never seem to work but I was getting a real temp deviation when driving on the flat, up hills etc. I eventuall took it to a radiator specialsi and they found 18 of 18 cores blocked. Anyway, I think the air con is thinking it's to hot. Mine is anycase does not use the car thermistat but it's own so maybe yours is the same. I onlt mentioned the other peice as I didn't want to see you pay for a proper core fluch if you don't have to.

[TonyH]

Sounds like a partially blocked receiver/drier to me. Becoming more and more blocked as moveable particals are pushed against the filter material, then with the system off for a period, the particals re-settle at a lower location (cause there's no pressure difference holding them against the filter anymore), or get bounced away from the filter by the car moving etc alleviating the blockage until the unit is switched back on and the process starts again.

Next time you notice it's not working, see if the clutch (the front plate of the compressor) is still spinning. If so then check your pipe temps. Hands are fine for this, if there is a partial blockage, there will be a temp difference either side of the blockage. If it's the receiver drier the pipe going in will be hotter than the pipe going out.

If the clutch is not spinning, and you are handy with a multi meter, check fr power either side of your pressure switch. If there is only power on one side, you have a pressure cut-out.


Something else, check for ice build up on the bigger of the two a/c pipes at the firewall. You may have a dirty evaporator coil (the one inside) and the coil is icing uop over a long period of use.

Hope this helps

Tony

[95CRUZA]

Thanks for that info Tony and steveandviv the temp guage doesn't move at all and is always in the normal range so it does sound more like what your talking about Tony, I'll hold off on the flush and check those things you mentioned.

cheers
Phil

[yowie]

i had mine regassed on Wednesday, and the mechanic found a faulty tx valve.

It wasn't letting the cold gas through the system. He charged the a/c system, while I was there watching, but there was no cold air out of the vents. There was pressure on the inlet side but no pressure on the outlet side. He said they can block and unblock sometimes when they are faulty.

He replaced it (not cheap) and it worked fine.

Incidently, I didn't know that the a/c cuts out if the temp gets too high.

Driving home to Vic from Sydney yesterday, the a/c kept cutting in and out. It was very hot, and the engine temp was hotter than usual. I was about to phone the mechanic to see what was happening. I backed off by about 10 km/h to let the engine temp drop, and the a/c stayed on.

It's time to check the cooling system.

[Peter @ Aawen4x4]

Thanks for that info Tony and steveandviv the temp guage doesn't move at all and is always in the normal range so it does sound more like what your talking about Tony, I'll hold off on the flush and check those things you mentioned.

cheers
Phil

You gotta be a little wary of 'not moving' std temp gauges, cos it might be that all that means is the gauge is just not sensitive enough to be working well at all! I've seen a number that when checked would sit in exactly the same place regardless of the temperature until the coolant was well over boiling point, with still no change showing on the gauge! And then there are those where when you get a quality temp gauge replacement you find that the vehicle coolant temp has been going up and down all the time as you drove, but the old std gauge just wasn't ever sensitive enough to show that the temp was fluctuating, sometimes right thru the range on the dial, just never showing any change!

So don't take the 'not moving' temp gauge as a surefire indicator that the temp isn't changing, you really gotta get it checked too. Your local radiator place might be concivinced to run the remote temp sensor over things and check it all out; or the local auto elec might run a multi meter across the back of the gauge to check that it IS working across the range, and not just stuck in the one spot! OR if you can't get to anyone like that, you can sometimes pluck the temp sender unit from the housing/block and drop it in a thermos of boiling water, maybe even a freshly boiling billy if you are in the sticks - hot off the campfire! Those little gas stove thingies up on the fender can work too! Doing that should let you see some movement more than the needle just sitting where it always sits, and unless you get some movement, you can never be sure that the std gauge is working correctly and reporting what's happening!?

Be very wary of the 'not moving' temp gauge!

[95CRUZA]

Yowie & Peter, I'm obviously going to have to look at all these things you guys mention, I have people where I am that I can get to check these things, really appreciate the input, I am actually away in NT working at moment, but will get them organised when I get back next month, if you think of anything else that would be great too.
cheers