Question about 740 cooling fan circuit

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geronimo

Re: 92 740 turbo wagon:

Got temp fix on the overheat problem. The fan Autozone sold me as a
replacement for the cooling fan was really not strong enough, not
enough CFMs, to adequately cool the engine. I did a temp fix on the
cracked recovery tank with automotive goop, and pulled the second fan
from my (down for a while) Camry. Installed this fan in the
740....its maintaining mid-scale now with AC on and in hot part of the
day.

I am going to buy a stronger cooling fan for the 740...actually two of
them, on separate fuses. I don't like the stock two-speed fan...its
better for reliability to have two separate ones. The camry fan and
autozone fan draw 8 amps. THe second fan I could wire up so its
switched through a temp switch....there is already some unused temp
switch screwed into the RH side of the fadiator, but its contacts are
open when the engine is up to operating temp. It might be bad, or
might be a N.C. type switch. Anyway I need to know if the coolant is
regulated at 180 deg. on this car or what, (it runs at mid-scale on
temp gauge) and then I can get some sort of temp switch that closes
maybe 5 degrees higher.
I won't be red-lining the alternator in this car just adding
another 8 amps will I? There are no aftermarket accessories installed
that would be pulling more amps that the stock 740 . Thanks Geronimo
 
geronimo said:
Re: 92 740 turbo wagon:

Got temp fix on the overheat problem. The fan Autozone sold me as a
replacement for the cooling fan was really not strong enough, not
enough CFMs, to adequately cool the engine. I did a temp fix on the
cracked recovery tank with automotive goop, and pulled the second fan
from my (down for a while) Camry. Installed this fan in the
740....its maintaining mid-scale now with AC on and in hot part of the
day.

I am going to buy a stronger cooling fan for the 740...actually two of
them, on separate fuses. I don't like the stock two-speed fan...its
better for reliability to have two separate ones. The camry fan and
autozone fan draw 8 amps. THe second fan I could wire up so its
switched through a temp switch....there is already some unused temp
switch screwed into the RH side of the fadiator, but its contacts are
open when the engine is up to operating temp. It might be bad, or
might be a N.C. type switch. Anyway I need to know if the coolant is
regulated at 180 deg. on this car or what, (it runs at mid-scale on
temp gauge) and then I can get some sort of temp switch that closes
maybe 5 degrees higher.
I won't be red-lining the alternator in this car just adding
another 8 amps will I? There are no aftermarket accessories installed
that would be pulling more amps that the stock 740 . Thanks Geronimo
Click to expand...


What rating is the alternator? If need be, you can always pop in a 100A
unit from a 740 Turbo but you should have plenty of headroom normally.
 
geronimo said:
Re: 92 740 turbo wagon:

Got temp fix on the overheat problem. The fan Autozone sold me as a
replacement for the cooling fan was really not strong enough, not
enough CFMs, to adequately cool the engine. I did a temp fix on the
cracked recovery tank with automotive goop, and pulled the second fan
from my (down for a while) Camry. Installed this fan in the
740....its maintaining mid-scale now with AC on and in hot part of the
day.

I am going to buy a stronger cooling fan for the 740...actually two of
them, on separate fuses. I don't like the stock two-speed fan...its
better for reliability to have two separate ones. The camry fan and
autozone fan draw 8 amps. THe second fan I could wire up so its
switched through a temp switch....there is already some unused temp
switch screwed into the RH side of the fadiator, but its contacts are
open when the engine is up to operating temp. It might be bad, or
might be a N.C. type switch. Anyway I need to know if the coolant is
regulated at 180 deg. on this car or what, (it runs at mid-scale on
temp gauge) and then I can get some sort of temp switch that closes
maybe 5 degrees higher.
I won't be red-lining the alternator in this car just adding
another 8 amps will I? There are no aftermarket accessories installed
that would be pulling more amps that the stock 740 . Thanks Geronimo
Click to expand...

No, you have lots of spare current available in the alternator. That
switch in the side of the rad should close when the coolant gets above a
certain temperature, 95 C IIRC, which is above normal operating
temperature.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
 
We got this Volvo from some motorheards who dropped a spare/good
engine into it. No telling if the alternator is even a stock one.
Unless there is some P/N or info stamped on it, I can't really
determine if its 70 amp, 100 amp or what.

If I could be sure that the computer controlled relay can handle 16
amps, I would just wire both 8 amp fans in parallel and let them run
together. There is an initial surge of about 12 amps for 24 amps
total, so its got to be able to handle that as well.
That temp switch is an unknown, it was definitely still open at
mid-scale (normal) operating temp. Its got male spade terminals on it,
its unused because these motorheads put in a radiator from some other
vehicle, and wasn't needed on this car.
I guess I could buy an adjustable temp switch, stick the bulb
sensor into the radiator fins, and set it so it activates the second
fan when the temp starts going a little higher than mid-scale. I guess
this might save a little on gas, by decreasing the electrical load on
the engine, right?


Geronimo
 
geronimo said:
We got this Volvo from some motorheards who dropped a spare/good
engine into it. No telling if the alternator is even a stock one.
Unless there is some P/N or info stamped on it, I can't really
determine if its 70 amp, 100 amp or what.
Click to expand...


Usually there's a big sticker right on it, it'll say something like
Bosch 100A in bold letters.
 
geronimo said:
We got this Volvo from some motorheards who dropped a spare/good
engine into it. No telling if the alternator is even a stock one.
Unless there is some P/N or info stamped on it, I can't really
determine if its 70 amp, 100 amp or what.

If I could be sure that the computer controlled relay can handle 16
amps, I would just wire both 8 amp fans in parallel and let them run
together. There is an initial surge of about 12 amps for 24 amps
total, so its got to be able to handle that as well.
That temp switch is an unknown, it was definitely still open at
mid-scale (normal) operating temp. Its got male spade terminals on it,
its unused because these motorheads put in a radiator from some other
vehicle, and wasn't needed on this car.
I guess I could buy an adjustable temp switch, stick the bulb
sensor into the radiator fins, and set it so it activates the second
fan when the temp starts going a little higher than mid-scale. I guess
this might save a little on gas, by decreasing the electrical load on
the engine, right?

Geronimo
Click to expand...

Relays usually have a voltage and current rating marked on them. If you
have the original relay, it'll have no problem with the 24 amp startup
current.

If there's no sticker on the alternator, then run the A/C and the 2 fans
and whatever else you'll have on, run the engine at 2000-2500 rpm and
see what the battery voltage stabilizes at.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
 
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