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Fan Speed

Right, my 156 3.0 has a small issue with cooling, which I want to do something about before the height of summer. Its got a brand new radiator on, but it does run a touch hot. Obviously when cruising at a steady speed it is fine, but in traffic the temperature rises quicker than I'd like, and the fan comes in to bring it down, which it does (slowly)

But right now, the top resistor has failed and has been taken out, so the fan isn't coming on at a high speed, but a fixed 'medium' speed. Which got me thinking about my options:

1) Replace top resistor, fan speed will be a bit higher and the car will cool a bit quicker.

2) Replace top resistor with a non-temp sensing resistor, so that once the temperature goes over the threshold to activate the fan, the fan comes on at full speed as if the car was fully overheating

3) Do either 1) or 2), and also hardwire in a switch, probably mounted in the ashtray, so I can manually turn the fan on or off.


Any comments?

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Re: Fan Speed

not sure of 1 & 2 as all of my cars have had single "flat out" fan speeds...

But Pud, don't go for number 3 dude, thats just silly! acceptable on a mk 5 cortina, but not on an Alfa

I'd find a more reliable way of running a single flat out speed on the fan via an auto relay/ sensor control

Last edited by alfaspence; 28-04-08 at 14:56.
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Re: Fan Speed

Also looking to fit in an oil cooler, but there is so little clearance between the filter and the bulkhead and I'm worried a sandwich plate, especially one with a thermostat in, would just take up too much room, making oil and filter changes inconvenient and increasing the chances of the filter seal being nicked when the filter is being replaced..
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Re: Fan Speed

best off running a sandwich type remote take off plate, and run a remote filter elsewhere but including a cooler into the circuit at the same time...
Thats what iam going to do with my 75 conversion, the only thing that holds me back is that iam not sure what size fittings i need to order.... bsp, i know what that is, but jic and the rest?
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Re: Fan Speed

I don't know anyone thats done that before.. I know you're familiar with the 24v engine but have you seen its placement in the 156? Access to the oil filter is difficult, but I've never heard of anyone fitting a take off plate and mounting the oil filter elsewhere..
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Re: Fan Speed

At the rear between motor and bulkhead? access ONLY from below? real PITA? similar to the 164 i took my 24v from if it is...
As for space.... well... yup its tight

It is do able, as a sandwich plate and the blanking cover is shorter than a stock filter by itself.
Hmmm, mind working here, std oil cooler is mounted low, n/s front corner behind bumper? (156) but yes i agree the 156 is alot tighter 'bay than the 164... placing remote filter could be a real dog sausage....
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Re: Fan Speed

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Originally Posted by alfaspence View Post
At the rear between motor and bulkhead? access ONLY from below? real PITA? similar to the 164 i took my 24v from if it is...
As for space.... well... yup its tight

It is do able, as a sandwich plate and the blanking cover is shorter than a stock filter by itself.
Hmmm, mind working here, std oil cooler is mounted low, n/s front corner behind bumper? (156) but yes i agree the 156 is alot tighter 'bay than the 164... placing remote filter could be a real dog sausage....
I think that'd be the only way to do it.. The only 156 with an oil radiator is the GTA, and its mounted in the O/S corner. In a standard 156, the power steering fluid cooler is mounted in the O/S corner.. In a GTA, they moved the power steering fluid cooler to the nearside corner so they could mount the oil radiator in the o/s..
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Re: Fan Speed

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I think that'd be the only way to do it.. The only 156 with an oil radiator is the GTA, and its mounted in the O/S corner. In a standard 156, the power steering fluid cooler is mounted in the O/S corner.. In a GTA, they moved the power steering fluid cooler to the nearside corner so they could mount the oil radiator in the o/s..
Oh... the 156 i looked at the other day had a cooler mounted n/s behind front bumper... it was a 2.5 24v tho... could have been a transmission cooler i suppose
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Re: Fan Speed

I would go for the fix and a hardwired fan.Belt and braces never did anyone any harm !!
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Re: Fan Speed

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Originally Posted by alfaspence View Post
Oh... the 156 i looked at the other day had a cooler mounted n/s behind front bumper... it was a 2.5 24v tho... could have been a transmission cooler i suppose
Only the GTA had an oil -> air cooler, 2.5 V6 & T.S. had oil -> water heat exchangers, so the 2.5 you are talking about must have had something done to it.. I'm not sure about a transmission cooler? Trying to remember what mine looks like from underneath, can't remember seeing a transmission cooler. What does it look like? Maybe there is one..
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Re: Fan Speed

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I would go for the fix and a hardwired fan.Belt and braces never did anyone any harm !!
Maybe, think I'll have a word with my mechanic about the feasibility of hard-wiring a switch in
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Re: Fan Speed

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Only the GTA had an oil -> air cooler, 2.5 V6 & T.S. had oil -> water heat exchangers, so the 2.5 you are talking about must have had something done to it.. I'm not sure about a transmission cooler? Trying to remember what mine looks like from underneath, can't remember seeing a transmission cooler. What does it look like? Maybe there is one..
it was quite chunky, about 6 or 7 inches long by b maybe 6 wide. But the thing i noticed most was how thick it was... a good 2 inches and appeared to have its own dinky cooling fan?

(and for those of you who are dirty minded, iam referring to an oil cooler, without alledged over exadurated male sizes )

The car was at auto break in Colchester (scrappy) was an '02 or '03 156 2.5 V6, not sure of transmission tho
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Re: Fan Speed

Maybe it was a Q-system model, my car definitely doesn't have that..

Anyway, as for fitting an oil cooler on a 2.5, I think it would have to be fitted in the N/S wing, like where the intercooler is on a 2.4 JTD. There's a fair bit of space there if I remember correctly
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Re: Fan Speed

if the space is there, brilliant! its the placement of the remote filter which is bugging me now...
but you have the 156, so its over to you
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Re: Fan Speed

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if the space is there, brilliant! its the placement of the remote filter which is bugging me now...
but you have the 156, so its over to you
Ah, but you're the DIY specialist.. I can just about manage to change my own brake pads and clean the air filter out..

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Re: Fan Speed

If you want the fan to only run at full speed, just remove the resistor and connect the two wires together.


But also remember that all 3.0 & 3.2V6 usually run a proper oil cooler instead of the oil/water heat exchanger. So the lack of an oil cooler will be adding additional heat to the coolant.
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Re: Fan Speed

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Originally Posted by alfaspence View Post
Oh... the 156 i looked at the other day had a cooler mounted n/s behind front bumper... it was a 2.5 24v tho... could have been a transmission cooler i suppose
Must have been a Q-System automatic.
They have an ATF cooler on that side.

The GTA ran a power steering cooler in that location and the engine oil cooler on the other side.

Last edited by David C; 28-04-08 at 20:49.
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Re: Fan Speed

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If you want the fan to only run at full speed, just remove the resistor and connect the two wires together.
So as soon as the ECU detects coolant temp reaching 92 degrees it would then trigger the fans, which would run at full speed.. What about the second stage, when it detects temperatures of 97 degrees or over?
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Re: Fan Speed

It will carry on running at the same speed (full speed).
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Re: Fan Speed

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The GTA ran a power steering cooler in that location and the engine oil cooler on the other side.
Yup, I have 2 direct air intakes on either side of the front lower grill.
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Re: Fan Speed

Great, think I might do this then. There is no thermistor in at the moment, just the single resistor, so all I'll have to do is cut out the normal resistor and join it up with a bit of wire. Brilliant!
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Re: Fan Speed

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Ah, but you're the DIY specialist..
Cheers bud, but i can assure you, i don't always get it right tho



Quote:
Originally Posted by David C View Post
If you want the fan to only run at full speed, just remove the resistor and connect the two wires together.
Cheers David! I didn't want to say that as iam not entirely "o fay" with the electronic controls of the later models
Didn't want things to go with a poof of smoke!

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Must have been a Q-System automatic.
They have an ATF cooler on that side.
Cool cool, now i know!
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Re: Fan Speed

Right, I've got everything out now (about time) and have worked out the resistors are actually in series, not in parralel. So there is always a fixed resistance between the fan and a full 12v, even when on hot.

So, as I am thinking about removing the resistors, I thought I better check to see how the fans cope with a full 12v straight from the battery. On thinner wires than what is fitted in the car's loom, the fans ran fine, albeit fast. A fair bit faster than I have seen or heard them before, but not massively so. And the wires didn't get hot, so there shouldn't be any problems there.

Basically, if I connect the two wires circled red together, this means the first fan gets a full 12v if the temp gets over 92. With the two wires circled blue are joined together (notice one of them has no end - this melted on the exhaust and has been since cleaned up), this means the second fan will get a full 12v if the temp gets over the next threshold, I think 97 degrees.

What does everyone think?

Last edited by Pud237; 02-12-15 at 14:12.
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Re: Fan Speed

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What does everyone think?
That is awful carpet!!!

Can't see why it shouldn't work ... although does anyone know what voltage the fan's normally work on? if it's less than 12V then directly supplying 12V (actually don't we get around 14V when the engine is running) will cause the fans to be loaded more than "normal" which may cause their life to shorten ...

... also don't the resistors smooth out any little spikes in the voltage? ... or am I getting confused with capacitors?? (been a while since I did A-level physics ...) ... obviously spikes may cause damage ...


... I can only think that Alfa added those resistors for a reason ...
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Re: Fan Speed

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... I can only think that Alfa added those resistors for a reason ...
The circuit runs via the resistors to produce the low fan speed.
The full speed fan circuit does not run via the resistors.

If the resistor(s) have failed the fan will not run at all until the engine gets so hot that the ECU turns on the full speed fan circuit.
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