Fan Switch Observation

[LannyL81]

Since installing aluminum heads I have noticed the electric fans are running now....never did before with the iron heads. I checked the switch and it is good, not shorted. So just wondering if this is "normal" operation due to the aluminun heads and higher compression or is it perhaps something else about to go really wrong for me?

Water temp is under the 200 mark and I have a 160 thermostat installed.

No other problems.

Comments?

 

[bill81vette]

I wonder if the aluminum heads are giving the sending unit a false(wrong) reading???
or is closing the circuit and running the fan....
the unit is set at about 234 degrees,for the fan to come on.
I don't see a problem with the fans running..

 

[Tim81]

Those new Alum heads conduct heat much better then the iron heads. FWIW my fan comes on around 200 degrees, I really do not see a problem with the fan comming on early as long as the motor is reaching normal operating temps....Tim

 

[LannyL81]

I do not think that their is a problem with the fans running....just something I noticed. The water temp gauge shows the same as always....so not sure how accurate it is since I changed out the original sender....but it shows about the same position as it did with the iron heads, actually two sets of iron heads.

I am assuming that since I bumped-up the Compression Ratio a bit...that engine just runs a bit hotter now...and perhaps I was on the edge of the fans coming on with the iron heads and never new it.

So far so good....I guess.

 

[LLC5]

I do not think that their is a problem with the fans running....just something I noticed. The water temp gauge shows the same as always....so not sure how accurate it is since I changed out the original sender....but it shows about the same position as it did with the iron heads, actually two sets of iron heads.

I am assuming that since I bumped-up the Compression Ratio a bit...that engine just runs a bit hotter now...and perhaps I was on the edge of the fans coming on with the iron heads and never new it.

So far so good....I guess.

What temperature is the cooling fan coming on?

 

[Peer81]

Some things I was thinking about...
Do you have an old (two wire) switch or a lower temp new one wired switch? If it is still the old one, maybe you have a short somewhere between the fans and the switch? Do the fans stay on even when you disconnect the wires from the switch? I don't think it makes any difference if you have iron or alu heads 200F will still be 200F.
If you have a 160F thermostat but the coolant is around 200F I think it's better to change back to a 180F thermostat and I think some cleaning in and around the radiator is in order. When I had a 160F thermostat in the coolant didn't go over the 160F (cold climat overhere, and original low compression) and by that the ECM didn't go into closed loop or it was pending between open en closed. With a higher thermostat your engine will heat up quicker as the minimum coolant temp will still be 200F (I think).

Greetings Peter

 

[LannyL81]

I am not sure at what temp the fan comes on at....just noticed the fan is on when I opened the hood after a short drive. Temp gauge is showing the same as it has always shown....just below the 200 mark.
It is the old two wire style and it is not shorted as the fan does not come on until after engine has run for awhile.

I have no idea if the temp sensor in the head is the one that originally came with the car or not...I would assume not. So it could be possible that the gauge is showing an incorrect temp. I would need to measure the coolant temp with a cooking thermometer and compare against to the gauge.
The radiator is clear....I just had it out for the top end change and it is good. Also it is about 6 years old.

As the air temp is quite hot here all summer and still not cool by any means, there would be little if any difference in the temp gauge reading between a 180 or 160 thermostat. Now with cooler air temps, the gauge should show a slight decrease at cruise..but not in traffic.

Looks like I have a few things to check-out. No Check Engine Lite, so I assume the CCC is going into closed-loop operation. I am going to put my DMM on the O2 output this weekend to check the A/F ratio out and I will attempt to take notice of when the fan comes on and what the temp gauge shows.
I was thinking about making myself a A/F ratio LED bargraph display to drive around with for awhile....to check how the carb is running. Easier to see than the DMM display.

 

[Tom Bryant]

You said that the electric fans never ran before with the iron heads. Was the connector plugged in and making good contact? It could be that you had a problem before but don't now. The last time I changed plugs I either removed the fan plug for access or disturbed it and the fans wouldn't run. They are supposed to run with the A/C on by the way. I pushed on the plug and found it wasn't on tight. Been ok since.

I would expect them to run with the A/C on or in city traffic. Mine cycle sometimes on hot days when I pull into the garage. Stopping the engine stops the coolant flow and heat will build in the heads shortly before the engine starts to cool. Probably more so with the alloy heads.

Tom

 

[Hib Halverson]

If your water temp is under 200, it is not normal for the fan to be running unless the fan switch you have is designed to close at that under-200 value. That would be unusual.

Do the fans run all the time when the key is on?

Is the temperature gauge accurate?