365 GT 2+2 overheat fuse melt problem

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michaelbalk330
Posts: 130
Joined: Fri Feb 06, 2015 8:28 am

365 GT 2+2 overheat fuse melt problem

Post by michaelbalk330 »

Please advise.
Friend asked me to help as his car was over heating and fans not turning on.
Here are the diagnostics:
1) #4 fuse melted but still conductive. #4 drives the fans and is supposed to be a 50A fuse ( per the cover) but looked like it was a 16A red fuse
2) both fans work when externally powered.
3)The thermostatic fan switch at bottom of radiator works correctly and activates at 183 degrees, but only the right fan turns on.
4) When AC turned on, No fan turns on at all.
5) No power to the left fan feed when wire checked with ohm meter.
6) Fuse box was rebuilt a decade ago and is similar overall to stock. when the AC turned on, a Bosch relay on the board clicks but I dont know if that means it is actually good.. The AC compressor clutch DOES work when AC turned on, and there is another new relay in the engine compartment for the clutch.
7) after replacing the fuse, it seems to me the #4 fuse and the relay are warmer than they should be.

My plan is to replace that relay and the fuse with a more correct amperage fuse, but not sure where else to look for why the Left fan wont come on. I guess I am perplexed why the fuse overheated but didn't blow..

Michael
Michael
1967 330GT #9693
1960 190SL
1967 Ducati 350 Sebring #04783
1959 Moto Guzzi Galletto #GNR93
1973 450SL
1988 Mercedes 300CE 5 spd
Timo
Posts: 216
Joined: Thu Apr 13, 2006 8:56 pm
Location: Riverside, California

Re: 365 GT 2+2 overheat fuse melt problem

Post by Timo »

Couple of suggestions:

First, when attempting to diagnose & correct any automotive, especially electrical problems involving multiple components as potential culprit, DO NOT just replace (or rebuild) any parts until absolutely sure they're broken (or malfunctioning) and more importantly, DO NOT replace multiple parts at same time. Problem may appear to get fixed, but can have other underlying causes.
Work systematically to check/eliminate each potential component or part in the entire system, even after finding one believed to be the cause.

Second, most common cause for electrical problems in older/vintage vehicles is usually grounding, often due to corrosion/oxidation, especially on wiring contact points.
Always start by checking that all wiring contacts are clean/tight and each component has a good ground.
Timo
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michaelbalk330
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Re: 365 GT 2+2 overheat fuse melt problem

Post by michaelbalk330 »

Those are good points and that's exactly what I always do. You can see from my notes that everything has been checked systematically. I did think of one thing this morning which was that the Bolt holding the ground from the fans has both ground terminals attached to it. While the boat itself has a good ground I did not undo it to see if each individual ground wire was in good condition .perhaps the left ground needs cleaning up.
Michael
1967 330GT #9693
1960 190SL
1967 Ducati 350 Sebring #04783
1959 Moto Guzzi Galletto #GNR93
1973 450SL
1988 Mercedes 300CE 5 spd
Timo
Posts: 216
Joined: Thu Apr 13, 2006 8:56 pm
Location: Riverside, California

Re: 365 GT 2+2 overheat fuse melt problem

Post by Timo »

EDITED REPOST: Usually these types of problems are very difficult if not impossible to advise on or help solve remotely (via i-net), but here's another thing to consider:
Were any or all of these symptoms known to be present before fusebox rebuilding, immediately after or have they developed just recently ?
Timo
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michaelbalk330
Posts: 130
Joined: Fri Feb 06, 2015 8:28 am

Re: 365 GT 2+2 overheat fuse melt problem

Post by michaelbalk330 »

fuse box rebuilt a decade ago and all was fine for last 10 years. I really think ground issues are paramount in these old cars, but am perplexed by the melted fuse plastic that didn't cause the metal part of the fuse to blow--- seems like a current problem causing heat, but it is was a 16A fuse in a 30A circuit, and it should have blown if there was a current issue.
Michael
1967 330GT #9693
1960 190SL
1967 Ducati 350 Sebring #04783
1959 Moto Guzzi Galletto #GNR93
1973 450SL
1988 Mercedes 300CE 5 spd
Jimmyr
Posts: 447
Joined: Thu Aug 19, 2004 11:20 pm
Location: Scottsdale, AZ

Re: 365 GT 2+2 overheat fuse melt problem

Post by Jimmyr »

Good contact between the fuse and the mounting tabs is critical. Be sure the clips are clean and hold the fuse tight. Also, the fuse end should be clean and bright. Any resistance in these high current areas will cause heat and relax the fuse fitting clips causing loss of power in that circuit. These areas should be inspected and serviced offten. This is a common problem whith this type of design. Jim
mdempsey
Posts: 183
Joined: Thu Jun 07, 2007 10:08 pm
Location: Huntingtown, MD

Re: 365 GT 2+2 overheat fuse melt problem

Post by mdempsey »

You can now get a new fuse block. I suffered similar issues with my 365 GT. Replaced the fuse blocks and all electrical issues vanished. I think there are a few posts on Tom's blog of me fixing issues on the fly while on the road. Fuse blocks were not cheap but some things are worth the $.
srslusso
Posts: 25
Joined: Fri Aug 04, 2006 5:35 pm
Location: Encino,Ca.

Re: 365 GT 2+2 overheat fuse melt problem

Post by srslusso »

Mark where can you get the new fuse block you mentioned ?
I may be looking for another 365GT 2+2 and you remember what happened to 11727 (bills old car).
Former owner
Several Vintage Ferraris
Incl T de F Zagato 0515
Lusso 33 years
2 Queens 11727 & 11835 looking for another now !
2004 575M 135175 now
mdempsey
Posts: 183
Joined: Thu Jun 07, 2007 10:08 pm
Location: Huntingtown, MD

Re: 365 GT 2+2 overheat fuse melt problem

Post by mdempsey »

I got my set from Rutlands. So I guess I would check with Motion
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