Air con

Submitted: Saturday, May 03, 2003 at 05:03
ThreadID: 4706 Views:1646 Replies:5 FollowUps:2
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My 4.2 nissan GU has a dodgy air con. On a good length trip the air con cuts out at 120 ks and cuts in after a while at 110ks. One aircon guy said there was nothing wrong, the other put more gas in it and now it cuts out at 110ks and back in at 100ks. We're usually travelling betweem Port Hedland and Broome and I would really like to be able to sit on 120 without cooking the kids. Can any one tell me how to fix this. There's not a lot of air con experts to choose from up here and I don,t want to spend $200.00 getting it wrong each time.
Thankyou in advance
Allan
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Reply By: Member - John - Saturday, May 03, 2003 at 07:21

Saturday, May 03, 2003 at 07:21
Hi Allan,

I believe that there is a high pressure cut out switch in the refrigerant line that stops the AC when the AC system gets too hot and the internal refrigerant pressure gets too high. I was told this by Kittles Nissan in Alice Springs and it possibly has been discussed on the Patrol forum as well.

Nissan say that it is a 'safety' switch. I believe it is another Nissan design fault!

Happy 4 wheeling

Woodsy
4.8 auto GU
AnswerID: 19034

Follow Up By: David N. - Saturday, May 03, 2003 at 08:45

Saturday, May 03, 2003 at 08:45
Yes, Allan is correct. You could simply bypass the switch, but having said that the system is probably overfull....
If you bypass the switch and then blew a pipe you'd void any warranty etc.- however me personally- I'd probably do it- as long as I had the condenser fan wired so it would always run when the A/C clutch is engaged. (The pressure builds rapidly with the compressor running and no flow through the condenser.)
Atleast on my model (GQ)there is both a low pressure switch and a high pressure one. (The low pressure switch avoids it running with low gas which would stuff the compressor due lack of oil circulation)
(Somebody is sure to jump down my throat and say how dangerous that is- but as an engineer I do have some idea what we are talking about here!!! The biggest risk would be blowing a pipe off which is highly unlikely!!!)
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FollowupID: 11953

Reply By: Member - Wherethefugawi - Saturday, May 03, 2003 at 12:35

Saturday, May 03, 2003 at 12:35
What type of refrigerant does it have...is it r134a or has your system been converted to another refrigerant. however on the face of it , it sounds like its either too much refrigerant (especially now that it apppears to cut out earlier), non condensibles and or either both, faulty HP safety switch and at last resort wrong type ie too small, condenser coil. A good mechanic should be able to sort it out and select a company who do a lot of servicing of airconditioning. Try having the refrigerant removed, system evacuated and recharged with new refrigerant...and there shouldnt be any need to replace the drier but is good practice if your not short of a $$. Also try a good airconditioning mechanic and i underline GOOD.

I might add that a retroifitted system, one that has been converted to a refrigerant that the auto industry seems to be pushing (other than R134a) may require a larger condenser at higher speeds. Cheers all
AnswerID: 19053

Reply By: Bob Y. - Qld - Saturday, May 03, 2003 at 15:30

Saturday, May 03, 2003 at 15:30
Allan,

You don't say whether your GU gets hot when this occurs. My experience with tojos is they'll shut the a/c down when the engine temp gets too high.

Have you checked radiator and condensor for insects, mud, grass seed etc, even to extent of removing radiator to give both a good clean. Blow out with air is best. Know from experience, well 30 years ago, that it gets bloody hot up that way.

hooroo...

AnswerID: 19059

Follow Up By: Member - John- Saturday, May 03, 2003 at 22:16

Saturday, May 03, 2003 at 22:16
Allan,
We have a Tojo 100 series wagon and two GU 4.2Td coil cabs in our work fleet based in Derby. We do a lotta miles on the highway in bloody hot weather. The Tojo aircon fades away as soon as you sustain >110km and that is normal, but the GU's seem to keep going OK unless it is really hot and the engine radiator starts working hard. We are meticulaous about keeping the radiators & condensors cleaned of grass seeds and bugs, usually have to remove the GU radiator every 20,000k and do it properly. Turbos do not like a degraded cooling system and that will pass on the the aircon over temp cutout as well.

Look for other defects, eg. electric fans not working properly, main viscous coupled fan not working propoerly, loose fan belt, etc. Do you have fine mesh screen in front to stop bugs & grass seeds? If so, they can cause more problems than they solve (use only temporarily when really needed)

JohnS
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FollowupID: 11974

Reply By: Allyn (Pilbara) - Sunday, May 04, 2003 at 00:04

Sunday, May 04, 2003 at 00:04
Get rid of it and get an 80 series !!!
AnswerID: 19075

Reply By: Wim - Sunday, May 04, 2003 at 11:11

Sunday, May 04, 2003 at 11:11
Allan.
A few thoughts on A/C problem.
1. Keep cond coil as clean as possible.
2. DO NOT bypass safety (HP) switch. Damaged valves on you comp = many $$$$.
3. At the speeds you are talking about, you may be getting too much capacity out of the comp in relation to the cond & evap coils. You may consider a pully change to slow the comp at high speed if you spend a lot of time at that speed..

RegardsWim
AnswerID: 19083

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