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Old 10-25-2000, 10:10 AM
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Just wondering if anyone knows what I could (or should) check before taking my car to the mechanic for my aux fan. I keep replacing the fuse (25A) whenever it blows (pretty bad I might say, torn back from the porcelain) and it just blows again when the engine gets hot in stop and go traffic.

The fan is not seized up as it moves freely by hand, and I haven't had any overheating problems as yet (I turn on the interior heat to cool the engine if nec.) but these electrical problems are always difficult to diagnose, and I'd rather spend the time than the labour of a shop.

Please advise, thanks.


1976 230(.4)
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Old 10-30-2000, 03:47 PM
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Anyone ???
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Old 10-30-2000, 03:57 PM
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Join Date: Jul 2000
Location: Toronto, CANADA
Posts: 1,193
Is the aux fan the only thing on that circut? I'm not familiar with your model, but on my 1986 420SEL, most of the circuts run several different things, most of the unrelated to each other and at different ends of the car. Check to see if anything else is running on that circut, maybe that is blowing your fuse. Other than that the only thing that should blow your fuse that violently (if it is not your fan) would be if the wires are borken or bare somwhere and the live is in contact with either the ground or neutral. This could evn be inside the switch maybe.

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Old 11-03-2000, 03:22 PM
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Yes, I do know that my rear defrost dosn't work as well it appears that my blower fan dosen't work either. (To get air, I have to turn on the A/C to use the fan settings) I wonder if there is a relay that controls them all that might be fried. I can't seem to locate the electrical info that would tell me either way what is the case.

1976 230.4 W115
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Old 11-05-2000, 07:39 PM
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Join Date: Jan 2000
Location: New Bedford, MA USA
Posts: 1,583
Aaron, does the fuse blow every time the fan activates. Not sure on your car, but a 25 amp fuse is pretty hefty. Although the control circuit should have at least one relay, if that's baked, then it wouldn't work at all. The fuse is protecting the secondary side of the relay-power circuit. It's possible your fan is drawing too much current when it starts up. All the items you mention are high current systems. I would be surprised if they were all on the same circuit. Try and find out exactly what is on that 25 amp circuit. The blower thing sounds unrelated, even if the climate control system is funky. I think that it's a pretty safe bet if all that stuff comes on at once, 25 amps is about half what you might need to get past the startup current draw. Good luck..

Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
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Old 11-05-2000, 09:17 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Pretty simple electricals on that old guy. The aux fan should have its own fuse. The TWO inside fans will be separately fused also. There are separate fans for A/C and heating/ventilation, your problem there could be the heater fan or the switchover system.

The A/C and aux fan were special versions on those cars and they had separate fuse boxes (two fuses). The aux fan was turned on by a thermal switch on the receiver-drier or the 212 deg switch on the T-stat housing. To see if the fuse blows with the fan try jumping each switch (one at a time)to turn on the fan. If it blows with either switch then try it with the fan disconnected and the wires insulated.

The relays and fuses are on the passenger side firewall if I recall. Switch relays as the next step. After that you should inspect the harness to the fan and if none of that works get a bigger stick (bg).

[This message has been edited by stevebfl (edited 11-05-2000).]
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Old 11-05-2000, 11:48 PM
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Thanks,guys I'll take a look at it tomorrow. As I remember, there are no visible switches on the stat housing (unlessyou mean below the top) The A/C fuse is on the passenger side, but the aux fan fuseis on the driver's side between the battery and the brake master cyl. There are two separate fuse boxes containing two fuses each there. the one closest to the master cyl, I beliive is for the sliding roof. The other box contains the aux fan fuses. Only one of these fuses keeps blowing.

It's the one on the outside of the engine. I'm not sure if I should mess with this myself, but it will be great to pass this on to my mechanic to take a look.

I haven't noticed any overheating at all, however my temp gauge jumps up and down like it's possessed once the engine warms up.

Thanks again,

1976 230.4
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Old 11-07-2000, 02:51 PM
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I took a look on the thermostat housing and I can't seem to find anything that looks like a switch to me. Are they electrical switches, or are you refering to the wire that extends off the top of the temp. sensor ?

1976 230.4 W115
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