For newer Civics I am finding that Mugen, Mishimoto, and it seems
Spoon make fan thermal switches that turn the fan on at a lower
temperature. It seems these are for racing, hence I have some hope
that you can find one for your generation. See for example
Mugen for one says to get a thermostat that matches up with the
I gather yours screws into the bottom of the radiator. The late 80s
ones screw into the back of the engine block. Still, it seems the
interchangeability is likely from looking for aftermarket thermal
switches. See for example
I think I might go over to the junkyard, forage for the switch on
various generations, and check to see if the mechanical fitting of the
later generation thermal switches works on your older Civic.
Exactly what I want to do.
The Gen II Civics had two sensors (on some models), one in the head near
the thermostat side and the on the lower radiator.
Oh, not many Hondas from 1980's in junkyards around here...
The issue is that the later Civics had a higher operating temperature
for emission control reasons. I'm just wondering if there is some sort
of coding to determine when a sensor will close the ground circuit.
I'm just trying to shorten the range between the thermostat and sensor.
That said, the current heat wave here will end today so this will be
less of a concern. The car is not overheating but the temp indicator
rises when idling until the fan kicks in. Needless to say, temperatures
indicators particularly on old cars are not exact by any means.
you can get aftermarket fan control units that have variable fan speed
outputs - will do what you describe perfectly.
however, i'd question your rationale for this. honda tested their
vehicles at extreme temperatures and if the cooling system is
functioning correctly, there should be no need for augmentation. no
point monkeying with fan control if the coolant circuit is blocked.
I'll probably swap out the sensor in the radiator.
Cooling system is in top condition including a nearly new radiator. It
just seems that the gap between the thermostat opening and the sensor
kicking the fan on is too wide. This only occurs in heavy traffic
waiting for a light. Even so, the temperature does not go into the
danger zone just a little too high for my liking. My other Civics don't
have these symptoms.
You mean the GAUGE goes up and down? Or does the IDLE go up and down?
Simply swapping temperature sensors is not the answer here. There is
something else going on.
The dashboard temperature gauge (like the gas gauge) has a damper component
that is supposed to prevent short-term fluctuation. If that component
starts to go bad, the needle will follow every movement of the thermostat.
The thermostat is opening and closing all the time, especially at idle.
What's the amplitude and frequency of the "modulation"?
The gauge will creep upward until the fan kicks in when waiting at light
No sudden movement(s). Simply a creep when stuck in traffic until the
fan kicks in.
Temperature gauges are not super accurate but I figure the temperature
modulates upward as much as twenty degrees when it occurs...
It's likely the switch is simply faulty and in need of replacement with one
exactly like it.
I've seen those switches fail three ways:
1) no power to fan
2) fan comes on too soon
3) fan comes on too late.
I suspect you have the third.
Could well be. I'll probably get around to "switching" it out maybe
next week. (After all, it's been doing this ever since I put it on the
road last September). why rush... (Oops, in retirement mode again).
Do you have a Honda workshop manual (OEM) for that Civic? The manual
should have the specs for the fan switch in it. With an ohm meter, a
good thermometer, and a pot of water that you can boil, you can check
whether the switch functions to the spec (including checking a new switch).
Looks like the problem may be #3). Maybe an IR thermometer (pointed
at the body of the switch) might tell you that.
These are the specs for a 1986 Accord in the OEM Canadian market manual.
(I don't have a Civic manual).
Fan-to-core clearance, 23mm (0.90")
Thermoswitch "ON" temp., 87C---93C (188F---199F)
Thermoswitch "OFF" temp., 83C (181F) or more (hysteresis 2C (3.5F) or
Looks like the above switch has a 'go, no go' spec (replacement context).
Regarding the '[sic]', it actually said '(hysteresis 2C (35F)'. They forgot
the decimal point. Why it has what appears to be a redundant 'or more'
beats me, but there was a transmission diagram, in the manual, that showed
a 'Frange' (the instruction text said 'Flange'). Jap to English translation
in manuals can sometimes be 'hysterical'.
snipped-for-privacy@FreeNet.Carleton.CA (M.A. Stewart) wrote in
Hopefully,he's replaced the thermostat already.(with an OEM model,and
the right temp)
I had the creep up/down temp gauge problem with my Integra,it was the
thermostat. temp climbed up at stops,dropped when moving.
Get the OEM specs and test procedure for those stats, and test them.
Make sure they're good. Test with the 'pot of water etc.' method. Record
your results. Hang the stat and thermometer in the pot with wire. Use an
The stats are from Honda for those, (Gen II), years. I put one in my
other '82 and it solved an overheating problem in it. I have high
confidence in the Honda labeled product.
The boiling pot test is way to involved for me.
I expect that your specs for the later Accord probably are the same as
my earlier Civic. Canada, (I believe), never had the complex carburetor
as did we as mandated by the good ol' EPA.
Gotta luv them thar' Japanese instructions though...
Don't make that assumption. Get the OEM specs for your car.
Canada, (I believe), never had the complex carburetor
Maybe identical. The emissions stuff was a little less (not much) than a
USA market Accord of the same year. Canada at that time lagged about
3 years or so behind USA re emission controls.
The 3Gee carbs are actually simple inside. The complex stuff was bolted/
attached to the outside of the carb. For example, the power valve (inside the
carb) is actuated by an external vacuum hose connected to the intake
manifold. Most other carbs incorporate that circuit inside the carb with
Some Datsun manuals called the passenger "the assistant driver"... what
the hell?... don't they have mother-in-laws in Japan, and know
that mother-in-laws should not assist in driving?
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