AC causing temp gauge to rise???

[MV99]

Ive noticed recently while driving intown that after the AC is on for about 20 minutes, the temp. gauge starts to rise. It gets a little too close to the red for my comfort level, so I keep turning it off at that point, This always makes the gauge move back down to normal. I keep it off for a few and then turn it back on, and the temp. begins to creep back up again....and it sure is hot outside these days... Any ideas what could be causing this???

[carlosz]

let us start by steps, of course the compressor puts load on the engine when
compressor is on. that said, do your auxiliary fans came on at any time during use of the a/c?... what about when temp is rising? they should.
on a classic those relays (a/c and fans) are located behind the washer fluid
container on the passenger side under the hood, also there is a thermoswitch on the uppper side of the thermostat housing, is you jump this wires you make the engine ECU think it is too hot and it activates the fans.
if the electric fans work normally, check your cooling fan clutch.
if your cooling fan clutch is working fine (a little drag if tunned by hand or a loud humm inmmediately upon start), check your thermostat, it should open fully at 190 degrees, this is done by feeling the upper radiator hose, after the gauge shows the normal operation temp be careful to feel the hose as it will be hot or better yet use a laser temp gauge.
if this is found to be normal we are getting into rough territory.
how old is your radiator, does it have too much scale, have it profesionally cored and or cleaned to make sure it flows normally.
too old replace it (ouch about 300 to 700 bucks depending were, remember we said "Rover" they hear "money").
if at all possible do an engine flush before sending the radiator to the shop, that way you have cleaned the inside of the motor and the radiator will have to be cleaned or replaced anyway.
by now you should have everything pretty clean and running cool.
during the flush of couse check to see if the water pump is working properly.
that is to say that water should create a a swirl when engine is revved or a movement could be seen when at idle..........................

how old is your motor, is it a tired unit, are you asking more than it can give?
what are your driving habits? do you expect the same pick up as when A/C is off.
what grade and weight motor oil Do you use? normal is 5w30 after 100k miles or so 10w40. heavy oil increases drag to the crank this in turn translates to heat.
Are you running too lean?, the leaner the hotter are you running with a vacuum leak this may be too rich also creates heat.
have you off roaded in a muddy area? have you made sure you do have a free flow of air thru the radiator and condenser?
do you have a winch or other equipement blocking the front grill.
these an many more assesments are the ones we make at shops when a customer comes in with your complaint.
in school they are quick to tell you that overheating or cooling problems on an engine are by far the most difficult and expensive to repair, quite often because the customer has neglected to recognise in time when they have a
problem or because they forget to tell you "it only happens when I tow".

sorry for the long post but rather than going back and forth on the forum I thought I would touch all bases to keep you occupied for a while.
if you have any Q's or concerns drop me a line
good luck.......
Carlos Zaragoza

[MV99]

Carlos,
thank you so much for all your information. Starting from the beginning of all that you wrote: I have not owned this car very long. So far my driving has been limited mostly to intown-stop and go. As far as the auxillary fans you were talking about: I have no idea if they are coming on or not. Is it an obvious sound that I should hear? Is this an easy fix??

thanks,
monika

[carlosz]

You are quite welcome......
Normally they are very quiet but then again nothing is normal in a land rover I should know I am dealer tech........
if you stand infront while everything is runing (grill area) there is a slight humm, if you run your hand on the grill you will feel a very cool soft vacuum pull. or of you spray a soft mist (water bottle) in to the grill you seeit dissapear, or simplt remove the grill and see.
all of these little tactics, simply because I do not know if you have any equipement infront of your grill which in turn may hinder ease of removal thereoff. I/E winch, offroad ligths brush guard etc.

[MV99]

Hey Carlos,
I tried putting my hand in front of the grill to feel for the air pull. I did feel it when the AC was on. I noticed a difference between when the AC was turned on and turned off....does that narrow things down a little?

[carlosz]

yes some what,
this shows at least 1- we have auxiliary cooling, 2- they work in junction with the a/c.
now it get a little trickie because we need to find if we are actually pusshing that air thru the radiator and condenser to the motor.
with the motor off ignition switch at position two and a/c on the fans should be running, place your hand inside the shroud infront of the cooling fan.
you should feel the push towars the motor. depending on radiator temp of course it will be warm or cold air.
while you are at it test the cooling fan cluth it should not turn freely rather it should have a little resistance.
if you can shine a light to the radiator check for leaves or mud blocking the cooling fins. if at all possible spray water to the radiator the engine side to the bumper side and see if you get clear water.
if water is not clear keep on spraying until you get clear water.

[p76rangie]

The reason that your temp rises when the air-con is on is that the air-con core in front of your radiator heats. Therefore it raises the air temp going through the radiator and reduces its cooling capacity. So any cooling system that is just surviving in normal temperatures will overheat when running the air-con. You do not say what year your Rangie is, but as already suggested, I would check that the electric fans in behind the grill and in front of the radiator are working. Depending on the model, there should be two fans. One should work whenever the air-con is swithed on, the other should come on when the car is hot.

The next I would check is your air-flow through the radiator and air-con core. I would preferably take the grill off to do it properly, but get the garden hose and force water through the radiator and air-con core from the front first and the from the engine side. Also a lot of garbage can build up between the two cores, which you can't see. Try and get into the gap between the two and hose any garbage out of the cavity.