80 series AC stops as temp rises????

G'day Brett,
I've heard a lot of blokes (mostly Toyota owners having a "shot" at my Nissan when I've been talking about this topic) say emphatically that their temperature gauge NEVER moves off normal.
Now I'm not disputing this in any way.......not one little bit.
However, here's what happened on my truck. It would do the same thing, except the Nissan's gauge would actually go up to just over half way and the air conditioning would switch off. I decided that I wanted to know what the ACTUAL temperature was at any time....not just some needle pointing somewhere in between a "C" and a "H".
So, I've now fitted a VDO gauge in addition to the normal gauge. The sender unit for this new gauge is mounted in a piece of stainless steel pipe which I've located half way along the top radiator hose. The results are quite an eye-opener and I would encourage all owners to fit one of these gauges.
What I have decided is that vehicle manufacturers design their temp gauges in a way that the owner will not worry about fluctuating temperatures. As such, my VDO gauge will be showing about 60oC when the Nissan's gauge reaches it's "normal" position of just under half way between C & H. The Nissan gauge will sit on that spot almost all the time when I'm driving.....almost never moves......
The VDO gauge will continue to rise from 60oC as the truck warms up and will go around 80oC around town. When I go on the highway and get up to 110k/h, the VDO gauge will rise to about 95oC, but if pushing into a headwind or going up a long hill, it can rise to 105oC.....All this time the Nissan gauge is still on "normal". It's not until the VDO gauge gets to about 110oC that the Nissan gauge starts to go the half way and beyond. So the "NORMAL" position of the original gauge could mean that the REAL temp is somewhere in a range of about 50 degrees Celcius.

So all those other vehicle owners who say their vehicle's temperature NEVER changes are kidding themselves......it's just that their gauge has been designed NOT to show them that the temp is changing.

As for the air cond turning off, I'm not sure if the 80 series has the same set-up as the Patrol, but my truck has a couple of switches screwed up into the bottom of the radiator. They are set so that one triggers the air cond to turn off at a certain temp. The other one is set to activate at a slightly higher temp and it turns the air cond's FAN back on (in front of the condenser/radiator) in an effort to force more air through if it is still getting too hot.

Hope this helps a bit,

Cheers

Roachie

Hi Brett,

Dead normal, I'd say. Just about all factory air-cond vehicles will have at least two shutdown switches built-in to the a/c system: a coolant temp high switch and a compressor head pressure high switch. That is, if the engine coolant temp gets too high or if the a/c compressor head pressure is excessive, the a/c will be shutdown.

The former obviously occurs if the engine is too heavily loaded while the a/c is on and the latter can occur for several reasons - but a clogged condenser is a high probability (which will also lead to high coolant temp, since the condenser is in front of the radiator).

Now, have you previously towed 2+ tonnes (Rocky + tandem trailer) in hot weather? If not, please realise this is very hard work for any vehicle and will show-up any problems which might never appear in solo work. (You say you have a Mike Vine turbo - so it's a reasonable bet you're in Qld or somewhere else pretty hot??)

About the 'almost not moving' temp needle, this is also common. Vehicle manufacturers (except maybe Nissan, Roachie?), generally build the coolant gauges not to move from 'normal' unless things are getting REALLY hot.

I put a thermocouple into my thermostat housing a few months ago and found that the standard gauge sits in the 'normal' position (just below half scale) while the actual coolant temp is anywhere between 88C (where the thermostat opens) and about 110C. From the few times it's done it, despite quite a bit of towing 2.2 tonnes in 45C+ ambients in the last couple of months, the a/c cuts out when the coolant temp exceeds about 114-115C - and that's when the standard coolant gauge JUST starts to move above the 'normal' position...

Overall, I'd say your 80-series was doing exactly what it should be doing in the circumstances. But, if you feel it should be handling the load you had on without dropping off the a/c (to reduce the cooling system load), I'd suggest looking at your a/c condenser and radiator for external fouling (bugs, grass seeds, etc.) or checking your radiator for internal clogging, etc.

Hope this helps.
Ian

Hi Brett the 80 series has a plug on the water inlet passinger side of engine if you unplug it it will fix your problem The 100 series dosent have it fitted .

Quite moprmal for a 1HZ in either an 80 or 75, as has been said there is a temp switch on the pass side front, high up that turns the a/c off if the engine gets too hot, I wouldn't bypass it it is there for a reason to prevent you overheating the motor.
On a 74 it is directly opposite the rod that holds the battery down, on mine they cable tied it to the rod which eventually led to the wiring breaking due to the engine movement. That is how I know where it is ;-))
Peter

As said above check out that switch or might pay to fit an electric fan in front of condesor to give it extra airflow,will also keep air con cooler when sitting in traffic. If it happens to do it again take a 2 inch piece of electrical wire with you strip back either end of it about 10 mm and locate your hi & low pressure switch for the air con either around the condesor or behind near head light and when in the same situation again pull up and quickly disconect the wireing loom connceted to the switch and insert the piece of wire you prepared into the connections of the high & low pressure wiring loom to bridge it out (wont blow any fuses so dont worry) and see if your air clicks back on if it does its the hi &low pressure switch doing it's job but also could be because you not getting enough air flow to cool the gas on the condensor. Sounds stupid that your getting enough for the radiator and not for the condensor but thats what happens, air con runs alot higher temp especially if you have prior to 94 model and the air con system is running the new gas in the original pump they run ahigher temp than the old gas,thats why you really need an electric fan for in traffic, sitting at lights etc. As I said in a previous post they dont fit electric fan to diesel motors only petrol. The only diesel I have ever seen with electric fan in front or the grille is on the 80 series Sahara and for 120k when I was working for toyota they bloody wel would want to fit one, but these also had climate air,makes you wonder these days if to get even an electric fan you have to buy top of the range even when its really required. If it has nothing to do with high & low pressure switch then I would also be looking at what has been said above. Everyone here to try and help. Have a great weekend. Regards Steve

Bret came in late on your question but had exactly the same problem on my 94 80 series with aftermarket turbo. AC would switch of under load with boat trailer behind. When temp dropped a little on less demanding roads the AC would cut back in again. Found problem was the viscous coupling fan hub. Fitted new hub problem solved. May help Eighty