hi all,

on my 86' SDL every time the aux fan comes on (high speed) fuse #1 will blow.
I've tested the fan with 12v direct to the battery and it works.
the car is running hot and will get to 105 in traffic (southern cali 95-100F ambient temps) I've replaced the temp switch (105/115 green) that trigger the high speed fan but still fuse #1 will blow.
any ideas? thanks in advance ,Eric.

Check the grounding points, and other possible cause for short circuit.

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Can you spin the fan freely by hand ??? ..and what size fuse ??

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A Dalton

Disconnect the fan and see if the fuse blows. If it does not, connect a DC ammeter in series with the fan to see how much current it draws if it will run momentarily before blowing the fuse. If the current being drawn is higher than the fuse rating, it is likely the fan causing the problem.

If the fuse blows with the fan disconnected, then there is indeed a short circuit somewhere. You will probably find it by visually examining all portions of the wiring route.

thanks for all the info. guys, ill keep troubleshooting per your advice. Arthur for your questions: yes i can spin the fan freely by hand and the fuse is 16A red.

OK
The early '86 had a problem with the wires under the fuse holder burning up and shorting, so you may want to look there first.
The Benz Remedy was they added an aux fuse holder in parellel with that one outside the F1 box and that eliminated the problem.

As posted , you want to know if the fuse is blowing due to load or short.
If you do not have an amp meter, just run the fan direct with a 16A fuse in- line and see if it holds..that will eliminate the fan draw as suspect.

Then you know wiring or connections are bad upstream..also look at the teminals on the R15 pre-resistor. Another common problem spot.

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A Dalton

Thanks again Arthur, ill do all the testing tomorrow.
I've just found the aux fan amp draw specs, that got me really confused the tech data for the aux fan: Auxiliary fan(max.speed)---approx 17.5A at 13V. the red fuse is only 16A, did i get it all wrong?