Turn Air Con Off, Engine Temp Goes Up

[rixalex]

For i think perhaps the first time ever, i had to turn off the air con in my car the other day as it was raining hard and quite cool. What i noticed, almost as soon as i did, was that the temperature reading in the dash for the engine started rising from its usual 1/3 position right up to almost 2/3. When i turned the air con back on, it instantly went back down again.My question is, is this normal?

[transam]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

[rixalex]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

Thanks for the idea TM. You could well be right. So based on what you are saying, if i continued on without turning the air con back on, the fan should kick in by itself eventually and the temp would then come back down. Right?

As far as the 1/3 thing goes, actually that is it's usual lowest setting point. More often than not, like when sitting in traffic, it is about the 1/2 point.

[transam]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

Thanks for the idea TM. You could well be right. So based on what you are saying, if i continued on without turning the air con back on, the fan should kick in by itself eventually and the temp would then come back down. Right?

As far as the 1/3 thing goes, actually that is it's usual lowest setting point. More often than not, like when sitting in traffic, it is about the 1/2 point.

Yep, unless the engine temp sensor for the fan is naff and the A/C is cotrolling the fan only. You can test that by leaving the A/C off, lift the hood and see if the fan works. Engine temp should be near constant, though l accept that rides with only electric fans and no mechanical fan do fluctuate a bit whilst turning the fan on and off waiting for temp change..

[rixalex]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

Thanks for the idea TM. You could well be right. So based on what you are saying, if i continued on without turning the air con back on, the fan should kick in by itself eventually and the temp would then come back down. Right?

As far as the 1/3 thing goes, actually that is it's usual lowest setting point. More often than not, like when sitting in traffic, it is about the 1/2 point.

Yep, unless the engine temp sensor for the fan is naff and the A/C is cotrolling the fan only. You can test that by leaving the A/C off, lift the hood and see if the fan works. Engine temp should be near constant, though l accept that rides with only electric fans and no mechanical fan do fluctuate a bit whilst turning the fan on and off waiting for temp change..

Thanks TM. Will check.

[transam]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

Thanks for the idea TM. You could well be right. So based on what you are saying, if i continued on without turning the air con back on, the fan should kick in by itself eventually and the temp would then come back down. Right?

As far as the 1/3 thing goes, actually that is it's usual lowest setting point. More often than not, like when sitting in traffic, it is about the 1/2 point.

Yep, unless the engine temp sensor for the fan is naff and the A/C is cotrolling the fan only. You can test that by leaving the A/C off, lift the hood and see if the fan works. Engine temp should be near constant, though l accept that rides with only electric fans and no mechanical fan do fluctuate a bit whilst turning the fan on and off waiting for temp change..

Thanks TM. Will check.

Any luck, conclusion.

[Tarric]

Just a guess , perhaps if the A/C condenser rad uses the electric engine rad fan, on turning off the A/C the fan stops for a while until a engine temp is reached, you turn the A/C back on, the fan starts up and does it's job. Eeeeeer or perhaps not, just a guess.

PS. 1/3 reading seems a bit low, most stuff 1/2 is the norm, perhaps the thermostat is iffy.

/\ This man knows the score. My car is the same way if you turn aircon and the radiator fan turns on, its a great way to keep the car from overheating if you have a stuffed thermostat

[LeCharivari]

It may not only be the thermostat - the relay for the fan from the thermostat may be stuck off, but the relay from the a/c still works and turns the fan on. Exactly the same test, except the fan (or second fan on some cars) doesn't come on at all. A new relay's a lot cheaper than a new thermostat, so check the relay too!

[OlafStapleton]

or no water in radiator.

[rixalex]

Yep, unless the engine temp sensor for the fan is naff and the A/C is cotrolling the fan only. You can test that by leaving the A/C off, lift the hood and see if the fan works. Engine temp should be near constant, though l accept that rides with only electric fans and no mechanical fan do fluctuate a bit whilst turning the fan on and off waiting for temp change..

Thanks TM. Will check.

Any luck, conclusion.

Thanks for the interest TM, and for everyone else's comments.

OK, well i tried what you suggested - popped the hood, started her up, and waited for the fan to kick in. It didn't. At least not in the five or so minutes i waited. Or would it take longer than that?

Turning the air con on and off instantly however kicked the fan into gear.

I guess all this means either the thermostat or relay is knackered. I'm also guessing that as i almost never drive the car without air con, it should be ok to continue driving her until such a time as she has a visit to the doctors.

[rixalex]

or no water in radiator.

More like, or no brain in head.

[WarpSpeed]

Yep, unless the engine temp sensor for the fan is naff and the A/C is cotrolling the fan only. You can test that by leaving the A/C off, lift the hood and see if the fan works. Engine temp should be near constant, though l accept that rides with only electric fans and no mechanical fan do fluctuate a bit whilst turning the fan on and off waiting for temp change..

Thanks TM. Will check.

Any luck, conclusion.

Thanks for the interest TM, and for everyone else's comments.

OK, well i tried what you suggested - popped the hood, started her up, and waited for the fan to kick in. It didn't. At least not in the five or so minutes i waited. Or would it take longer than that?

Turning the air con on and off instantly however kicked the fan into gear.

I guess all this means either the thermostat or relay is knackered. I'm also guessing that as i almost never drive the car without air con, it should be ok to continue driving her until such a time as she has a visit to the doctors.

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

It may be the relay however the relay is working to some point as it turns on the fan when the A/C is turned on so it isn't completely non-functional and the likelihood it is partially functioning is slim though not impossible as it's only function is to turn the fan on and provide a direct current from the main to accommodate a higher load without blowing fuses.. More and more is pointing to the thermostat..

[Lickey]

Usually by turning on AC it loads the engine, making it run hotter, perhaps your particular model brings it in anyway? you could test it another way, Put AC on, let car tick-over, wth bonnet up, does fan cut in and out or just keep going? should cut out along with AC when cab is cool enough.

[rixalex]

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

I'm fully aware it is not time based but as i don't have a digital readout of what the engine temperature is, it makes it difficult to give that type of information. I assumed that by saying i left the engine running for five minutes, people would have some rough guesstimate of what the temp would have reached and whether it would be hot enough to kick the fan in. Turning over your engine from cold, how long would you guess your car takes?

It may be the relay however the relay is working to some point as it turns on the fan when the A/C is turned on so it isn't completely non-functional and the likelihood it is partially functioning is slim though not impossible as it's only function is to turn the fan on and provide a direct current from the main to accommodate a higher load without blowing fuses.. More and more is pointing to the thermostat..

Thanks.

[WarpSpeed]

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

I'm fully aware it is not time based but as i don't have a digital readout of what the engine temperature is, it makes it difficult to give that type of information. I assumed that by saying i left the engine running for five minutes, people would have some rough guesstimate of what the temp would have reached and whether it would be hot enough to kick the fan in. Turning over your engine from cold, how long would you guess your car takes?

A digital readout isn't necessary, and your ASSumption is in correct as for people to go out of their way and try to give you enough information over an INTERNET forum to help you out they need more accurate info. I.E. I let it run for about 5 minutes and the temp got to overheating, I. E. it boiled over or it just got to half way etc.. But no problem then I'll just let the "pros" here yourself included continue to speculate and guess without having the proper info to do so accurately, I've better things to do with my time then to bother helping people with an axe to grind..

I wouldn't guess or make ASSumptions about how long my car takes to heat up because it isn't YOUR car and EVERY one is different with different quirks, like women...For a relevant example MY car doesn't have the problem YOUR car does..

Edited August 4, 2011 by WarpSpeed

[rixalex]

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

I'm fully aware it is not time based but as i don't have a digital readout of what the engine temperature is, it makes it difficult to give that type of information. I assumed that by saying i left the engine running for five minutes, people would have some rough guesstimate of what the temp would have reached and whether it would be hot enough to kick the fan in. Turning over your engine from cold, how long would you guess your car takes?

A digital readout isn't necessary, and your ASSumption is in correct as for people to go out of their way and try to give you enough information over an INTERNET forum to help you out they need more accurate info. I.E. I let it run for about 5 minutes and the temp got to overheating, I. E. it boiled over or it just got to half way etc.. But no problem then I'll just let the "pros" here yourself included continue to speculate and guess without having the proper info to do so accurately, I've better things to do with my time then to bother helping people with an axe to grind..

I wouldn't guess or make ASSumptions about how long my car takes to heat up because it isn't YOUR car and EVERY one is different with different quirks, like women...For a relevant example MY car doesn't have the problem YOUR car does..

Were you born this way?

P.S. For the record, any future requests for help i may make, just take it as a given will not include you. Thanks, but no thanks.

[transam]

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

I'm fully aware it is not time based but as i don't have a digital readout of what the engine temperature is, it makes it difficult to give that type of information. I assumed that by saying i left the engine running for five minutes, people would have some rough guesstimate of what the temp would have reached and whether it would be hot enough to kick the fan in. Turning over your engine from cold, how long would you guess your car takes?

A digital readout isn't necessary, and your ASSumption is in correct as for people to go out of their way and try to give you enough information over an INTERNET forum to help you out they need more accurate info. I.E. I let it run for about 5 minutes and the temp got to overheating, I. E. it boiled over or it just got to half way etc.. But no problem then I'll just let the "pros" here yourself included continue to speculate and guess without having the proper info to do so accurately, I've better things to do with my time then to bother helping people with an axe to grind..

I wouldn't guess or make ASSumptions about how long my car takes to heat up because it isn't YOUR car and EVERY one is different with different quirks, like women...For a relevant example MY car doesn't have the problem YOUR car does..

[WarpSpeed]

It's not timed it's based on temp so if it reached or exceeded temp in that amount of time is debatable since you don't mention it, only "time" of 5 minutes..

I'm fully aware it is not time based but as i don't have a digital readout of what the engine temperature is, it makes it difficult to give that type of information. I assumed that by saying i left the engine running for five minutes, people would have some rough guesstimate of what the temp would have reached and whether it would be hot enough to kick the fan in. Turning over your engine from cold, how long would you guess your car takes?

A digital readout isn't necessary, and your ASSumption is in correct as for people to go out of their way and try to give you enough information over an INTERNET forum to help you out they need more accurate info. I.E. I let it run for about 5 minutes and the temp got to overheating, I. E. it boiled over or it just got to half way etc.. But no problem then I'll just let the "pros" here yourself included continue to speculate and guess without having the proper info to do so accurately, I've better things to do with my time then to bother helping people with an axe to grind..

I wouldn't guess or make ASSumptions about how long my car takes to heat up because it isn't YOUR car and EVERY one is different with different quirks, like women...For a relevant example MY car doesn't have the problem YOUR car does..

Were you born this way?

P.S. For the record, any future requests for help i may make, just take it as a given will not include you. Thanks, but no thanks.

Yes, I was born very intelligent and learned quite a bit a long the way, shame you weren't so lucky.. And your welcome BTW your attitude is why so many people think most Brits are such knobs and they're correct....

Edited August 4, 2011 by WarpSpeed

[transam]

I

Yes, I was born very intelligent and learned quite a bit a long the way, shame you weren't so lucky.. And your welcome BTW your attitude is why so many people think most Brits are such knobs and they're correct....

With a post like that l think you should sit back and think about what you were really born with.

[saintofsilence]

Just a guess but it would be worth checking if you have a blocked radiator .

[LeCharivari]

It may be the relay however the relay is working to some point as it turns on the fan when the A/C is turned on so it isn't completely non-functional and the likelihood it is partially functioning is slim though not impossible as it's only function is to turn the fan on and provide a direct current from the main to accommodate a higher load without blowing fuses.. More and more is pointing to the thermostat..

Rixalex, I'm sure WS was trying to help.

Either relays work consistently or they don't (they're not fussy about where their power comes from), so if you only have one relay to the fan controlled by both the A/C and the thermostat and it always comes on with the A/C, then its either the thermostat or the wiring (a loose connector?). On many cars the A/C and the thermostat would control different relays and it is probable this is the case with yours - so if you have two relays for the fan that means it could still be either the relay or the thermostat (or a loose connector/broken wire between the two).

Regarding time/temp, its difficult to know how long it would take to get hot; watch the dial and if it keeps climbing past 2/3 and the fan doesn't come on you'll know you've got a problem!

[rixalex]

Just a guess but it would be worth checking if you have a blocked radiator .

Thanks. Will check.

[rixalex]

It may be the relay however the relay is working to some point as it turns on the fan when the A/C is turned on so it isn't completely non-functional and the likelihood it is partially functioning is slim though not impossible as it's only function is to turn the fan on and provide a direct current from the main to accommodate a higher load without blowing fuses.. More and more is pointing to the thermostat..

Rixalex, I'm sure WS was trying to help.

In his own way, he may have been, but he was also telling me what a knob i was (apparently this is connected to the fact that i am British), and how he has much better things to do with his time. Now this might just be me, but when help is being offered in this sort of spirit, i really feel i'd be better off without it, no matter how insightful it might be, or, better still, with the help of people who are actually motivated by no other reason than that of wanting to help, such as yourself.

Many thanks for your comments below. Will look into it.

Either relays work consistently or they don't (they're not fussy about where their power comes from), so if you only have one relay to the fan controlled by both the A/C and the thermostat and it always comes on with the A/C, then its either the thermostat or the wiring (a loose connector?). On many cars the A/C and the thermostat would control different relays and it is probable this is the case with yours - so if you have two relays for the fan that means it could still be either the relay or the thermostat (or a loose connector/broken wire between the two).

Regarding time/temp, its difficult to know how long it would take to get hot; watch the dial and if it keeps climbing past 2/3 and the fan doesn't come on you'll know you've got a problem!

[rixalex]

Yes, I was born very intelligent and learned quite a bit a long the way, shame you weren't so lucky..

You forgot to mention the bit about you being a hero (of the self-confessed variety).

[WarpSpeed]

It may be the relay however the relay is working to some point as it turns on the fan when the A/C is turned on so it isn't completely non-functional and the likelihood it is partially functioning is slim though not impossible as it's only function is to turn the fan on and provide a direct current from the main to accommodate a higher load without blowing fuses.. More and more is pointing to the thermostat..

Rixalex, I'm sure WS was trying to help.

Either relays work consistently or they don't (they're not fussy about where their power comes from), so if you only have one relay to the fan controlled by both the A/C and the thermostat and it always comes on with the A/C, then its either the thermostat or the wiring (a loose connector?). On many cars the A/C and the thermostat would control different relays and it is probable this is the case with yours - so if you have two relays for the fan that means it could still be either the relay or the thermostat (or a loose connector/broken wire between the two).

Regarding time/temp, its difficult to know how long it would take to get hot; watch the dial and if it keeps climbing past 2/3 and the fan doesn't come on you'll know you've got a problem!

Thank you for your insightful post..