Motor overheating, fans starts when pushed only

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MrXantia
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Motor overheating, fans starts when pushed only

Post by MrXantia »

Xantia 1.8 16V 1998. Resently my engine has been overheating when I run idle for a loger period or drives in very slow traffic[xx(]. I opened the bonnet and after the engine had reached 100 deg. C I tried to push-start the fans one by one, then they began turning[:p]. Very slow at first, increasing speed until they almost sounded normal and eventually cooled the engine down and the thermosensor shut down the fans again. After a little while, still in idle, the temperature reached 100 again, and the fans didn't start[V], again. I pushed them, and they started as before[:(].
I unplugged the 3 relays between the two fans and tested them, they are ok. What else can I check?[?].
Any help is most welcome, because I'm driving on vacation this thursday.
Thx.
peter1138
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Post by peter1138 »

Sounds like the fans themselves have seized up...
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Post by MrXantia »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by peter1138</i>

Sounds like the fans themselves have seized up...
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Both at the same time? I guess it could happen... Murphys law and all...
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Post by Homer »

Could be one is sticking and pulling current away from the other?
I'm not an electrician so that could be completely impossible.
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Post by MrXantia »

No Homer, I dont think so, because it doesn't matter which one I start first, the other one doesn't start by itself anyway.
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Post by AndersDK »

Check the voltage feed to the fans !
You've got a typical symptom of too low voltage, making the fan motors too weak to start.
At lo speed the fans would be series connected, at hi speed both are feeded off full +12V.
My bet you have a corrosion problem somewhere in the wiring, causing a voltage drop.
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Post by rabenson »

I agree with Anders - worth checking the earth connections too!
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Post by MrXantia »

Well, as I was going to be driving to England I thought I'd rather have the shop look at it, and their verdict was "shot fans". Of course, I know they have an interest in saying this, so I want to find out if they are right. Where are the fans connected to the power? There are 3 relays between the fans, from there to the powersource I guess, but where should I look for the corroted connector?
BTW, the trip to England went well. No overheating problems, never over 90 deg. C in queues. But the morning traffic in Denmark will kill the engine on a hot afternoon for sure, so I need to get this done soon.
Lars Peter
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Post by bxbodger »

You could try disconnecting the fans, and applying a 12v feed directly from the battery,thereby by-passing all the intervening wiring and connections; that way you will know for definate if they are faulty or not.
If they start straight away, then no problem with them and you should start looking at connections and earths, if they STILL need a push, then they are most likely to be faulty.
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Post by AndersDK »

Hej igen Lars [;)]
First of all - find the wires running directly to the fan motors, these can be seen fairly easy. Then test the fan motors by disconnecting these wires, and feed the motors directly from battery.
This will immediately tell you which direction you must choose on the problem.
In case the fans wont run, problem is obvious.
In case the fans runs perfect with a direct feed, you're facing the worst problem for the average car DIY'er : tracing electric faults.
Best method is simply to follow involved wiring backwards, checking all connections you find, until you reach the earth points and the 12V feed points, and any relays.
Relays are checked by substitution. You can use standard change-over relays from any car shop. But most often the problem is corroded spade connctor pins on the relays.
At times you find the mysterious dreaded black copper corrosion under the cable isolation, which makes even heavy gauge cables trash. Nothing else to do but replacing the cable then.
Using this method, even the first timer DIY'er can find and rectify most electric problems, not having any documentation at hand.
Observe these 2 important points :
1) When tracing a blowing fuse problem, NEVER replace with a heavy wire. Instead use a high wattage (headlamp) bulb instead. This will VERY clear show WHEN the problem is present, not burning out the circuit wiring.
2) When testing a wire carrying +12V feed, NEVER rely solely on a voltmeter. Test the 12V feed in fact can feed power, loading the +12V feed with a headlamp bulb.
This means your first job is to fiddle up a headlamp bulb with some good long testwires terminated in spade (male) connectors. Then you have a simple and very handy testgear.
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Post by MrXantia »

Thanks to Anders and bxbodger. You were helpfull pointing out the most obvious way (as always) to find the fault. In fact the fans act in exactly the same way, so they must be shot. New (used) ones are around 56£ each, so I guess its just changing them next weekend.
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