Need help with some electrical questions.

[dj_alto]

See, I got this 88' Civic DX HB and its all fine n' dandy, but when i bought the car I failed to realize that the cooling fan never turned on. I've done some diagnostic work (checking switches, relays, and wiring) but to this day, i still can't figure it out...I've changed the thermo fan switch and the temp. sending unit...and still nothing...

If anyone knows anything that could assist me in this, please reply or email @ dj_alto@shawca...


Thanks a bunch...

Alan

[ivymike1031]

have you pulled the plug off of the fan and checked to see whether it ever gets power?

[dj_alto]

i did do that but the fan never turned on so there was no voltage...i disconnected the fan swith from the back of the engine and the jumped the two wires together. When I did that, the fan turned on...so i know that the fan does work, i've checked the relay switch and its working fine...

n e thing else?...

thx

Alan

[dj_alto]

and there is no plug on the fan....

[ivymike1031]

Originally posted by dj_alto
[b]i did do that but the fan never turned on so there was no voltage...i disconnected the fan swith from the back of the engine and the jumped the two wires together. When I did that, the fan turned on...so i know that the fan does work, i've checked the relay switch and its working fine...
n e thing else?...

So you're saying that you've identified the only thing that's keeping the fan from turning on, but you want to know something else that could be the problem?

Sounds to me like one of two things:
1) the switch that you jumpered is the problem
2) there is no problem with the fan circuit

I've got an 88 dx hatchback too, and I don't recall the fan being hardwired to the car - I remember being able to unplug it.

Since you said that you changed the temperature sending unit, presumably it's because your gauge says that the car is overheating?(sending unit is what moves the gauge & doesn't affect the fan) Have you considered the possibility that the gauge itself is bad?

[dj_alto]

im pretty sure that it works...would the temp gauge make a difference if the fan went on?...cus while i was driving the car, the needle moved until my engine got hot...but when it did, the needle just shoots up...

thx

alan

[b16a3sol]

replacing the switch that was bypassed during troubleshooting should solve the problem like ivymike said. the test would be to warm the car up and put a voltmeter on the wire to see if the fan is getting any power. just keep moving up the wire until a charge is found and assume that whatever you passed is the problem. replace the faulty part and you are done.

im kind of curious as to how you are not running hot without a fan cooling the car down. it sounds to me that the gauge works fine because the car should be running warmer than normal because of the lack of forced airflow from the fan.

[dj_alto]

the engine does get hot, thats why i don't drive it now...the only plug on the fan is the one that comes from the relay switch next to the air filter which makes the connection...i think i should just take it to a diagnostic place...


if n e one else gots n e more suggestions...plz reply...thx

[ivymike1031]

The engine is supposed to get hot! The thermostat doesn't even open until the coolant is about 180degF (so it doesn't use the radiator until then). There's no way you can hold your hands under the hood and accurately say "oh, it's too hot." Does steam come out of the overflow tank when the gauge goes to the top? Does the radiator cap start spraying coolant?

If you want to know what I think the problem is, it's the gauge. If you don't believe me, think about this:

How long does it take for the engine to get warm enough that the gauge starts to read in the normal range? About 10 minutes? How long until it gets a little bit higher than it's supposed to be? Another 5 minutes? How much longer until the gauge hits the top? Like 30 seconds, right? Does it seem reasonable to you that the engine is suddenly dumping a whole lot more energy into the coolant? Of course not. The gauge is going up too fast.

Still don't believe me? Try the following:

* Get a cooking thermometer
* Get a multimeter
* Suspend your thermostat in a pot of hot water (hang it from a string)
* Heat the water until the thermostat starts to open. The temp should match the temp on the box (you just replaced it, right?).
* Set the multimeter to measure continuity, and attach it to the two leads on the fan switch
* Heat the fan switch until the dmm reports continuity (switch closed). The temp should be a little higher than the thermostat opening temp (I don't have a spec here, but I can look one up later)
* Heat the sending unit and track resistance vs temperature. I'll look up the spec on that later

When you've done all of the above, I expect that you'll find that all of the aforementioned components are working just fine, yet somehow that pesky gauge still indicates "too hot." You can replace it, learn to ignore it, or do what I did (my '88 dx had the same problem). I put a variable resistor inline with the temperature sending unit, and dialed-in the correct reading on the gauge when the engine warmed up. It kept the gauge reading fairly accurately for another year after I started having trouble. Then the gauge finally quit altogether. Currently it will read the right temp until the car is almost warmed up, then it will drop to zero and won't turn on again until the car is cold & re-started.

If you don't feel like dealing with it, you can sell the car to me (for the right price).

[dj_alto]

thanks a lot man...really appreciate it...i'll try all that stuff this week...


Alan