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  View original topic: radiator fan fuse getting really hot!
karush Mon Jul 09, 2012 7:31 pm

I've got an 81 diesel vanagon with a later model radiator but original fan motor. The fuse #7 got so hot it melted the plastic cover. The thermo switch is working fine and wires and ground seem fine. The fuse that was in there was a 16 amp(it hadn't even tripped) and I replaced it with a 25 amp but still gets so hot after running for a minute or so that a wet finger sizzles upon contact! Could the fan motor be drawing more amps than normal? It runs strong and free. How can I figure out where the problem is? Thanks, Paolo.

AdrianC Tue Jul 10, 2012 1:24 am

I'd start by cleaning the fuse contacts.

If the fuse hasn't popped, then uprating the fuse won't solve it heating up - because it's still not drawing 16A. It's just getting too hot whilst drawing less than 16A.

jptech Tue Jul 10, 2012 2:44 am

Hi Frtend,

If the VW specified fuse hasn't blown then the current isn't excessive. More likely there's excessive resistance where the fuse holder tangs attach to the fuse box internals which generates unwanted heat.

Get a fire extinghisher and loosely connect the negative batt cable for a quick disconnect if needed. You'll also need a good digital multi-meter and the skill to use it.

Contact me when you're ready.

John

MarkWard Tue Jul 10, 2012 6:20 am

Here is the problem. The later fan uses more current than the early fan. If you check the Bentley manual, I believe the radiator fan from the later years takes a 30 amp fuse. The early vanagon fusebox is actually from the Beetle. It is rated for no more than 16amp loads per circuit. So, what is happening is your are exceeding the load of the fuse box, not the fuse itself. The fix is to take the wires off the fuse box from the back and install either an inline fuse or a circuit breaker. This will solve the problem.

crazyvwvanman Tue Jul 10, 2012 7:53 am

Read the OP again, he said it was the original fan motor still.

Quote: I've got an 81 diesel vanagon with a later model radiator but original fan motor.

The idea of moving the fan wiring to an independent fuse is a good one though. I have done that a couple times to 82 DV with the original fan. I powered the fuse with a separate power wire from the battery. That sure made the fan run faster at each speed. In one I used the same large new feed wire to power headlight relays. That sure made the headlights brighter.

The 80-85 fuse panel is marginal, more so with age. I have seen many with heat damage, often at the rad fan fuse.

Mark

rsxsr wrote: Here is the problem. The later fan uses more current than the early fan. If you check the Bentley manual, I believe the radiator fan from the later years takes a 30 amp fuse. The early vanagon fusebox is actually from the Beetle. It is rated for no more than 16amp loads per circuit. So, what is happening is your are exceeding the load of the fuse box, not the fuse itself. The fix is to take the wires off the fuse box from the back and install either an inline fuse or a circuit breaker. This will solve the problem.

MarkWard Tue Jul 10, 2012 10:06 am

Missed that. Either the wiring/ connectors have too much resistance causing the amp draw to go up, or the fan is on it's way out and is drawing too much load. You should verify the amp load with an amp meter when it is running.

Also, I am not sure where you are driving, but my diesel radiator fan almost never came on and when it did, it ran for no longer than a minute max. Seems like yours is running a lot and may indicate another problem.

karush Tue Jul 10, 2012 4:42 pm

Thanks for the replies.
How many amps do the old and new fan motors draw? I'm assuming it's the original motor but it's always possible someone else switched it. What's confusing me is that I've run 30,000 miles with that fan and fuse doing just fine and now all of a sudden it starts getting super hot. I have a good digital meter but don't know where to start exactly. Thanks, Paolo

crazyvwvanman Tue Jul 10, 2012 4:56 pm

More electrical resistance gives LESS amps flowing in a circuit. The problem with the early fuse panel is heat, from slight extra resistance at the fuse tip contact points. That contact heat builds up and can melt the plastic around the fuse holder and even the fuse panel cover. Cleaning the contacts of the fuse holder and putting in a new fuse may help. But the spring tension of the fuse holder can be damaged by the heat, particularly if the plastic melts and lets the contacts spread wider.

The case for motors is different. They can pull a lot of amps while trying to spin up to normal speed and if there is some mechanical reason why they can't fully spin up quickly then the duration of the higher amp flow can heat things in the wiring path up to the point of damage unless the fuse blows. That is also why increasing the fuse size on a motor circuit is unwise.

Mark

rsxsr wrote: ....... Either the wiring/ connectors have too much resistance causing the amp draw to go up,.........
........ or the fan is on it's way out and is drawing too much load. You should verify the amp load with an amp meter when it is running. .......

MarkWard Wed Jul 11, 2012 6:37 am

As far as the rated load, I believe you could use Ohm's law to calculate it. However, the factory fused it with a 16 amp fuse, while the other fuses are 8 amps for the most part. So, the amp draw would be between 8 and 16 amps. On startup the amps could spike somewhat higher.

I managed to overheat my box trying to run a later radiator fan when I installed AC. I did not really think it through completely at the time I wired in the AC. I was using the stock fuse to run the radiator fan on medium when the AC pressure closed the high pressure switch. Just like you, I added a 25 amp fuse, but I knew that the fuse rating for the later fan was 30amps. My reasoning was if the load was too much the fuse would pop. It ended up the weak link was the fusebox and the fuse tangs not the fuse. I have since moved the load off of my fusebox with and am using a circuit breaker now for the medium speed of my radiator fan. I also replaced the fusebox and cover with a new one. Cip1 sells the boxes and covers for the older vanagons for a very reasonable price. It installed easily. I dropped the old box and one by one moved the wires over to the new one. Worked out great. http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC%2D111%2D937%2D505%2DM

arrow Thu Oct 11, 2012 5:49 pm

karush wrote: I've got an 81 diesel vanagon with a later model radiator but original fan motor. The fuse #7 got so hot it melted the plastic cover. The thermo switch is working fine and wires and ground seem fine. The fuse that was in there was a 16 amp(it hadn't even tripped) and I replaced it with a 25 amp but still gets so hot after running for a minute or so that a wet finger sizzles upon contact! Could the fan motor be drawing more amps than normal? It runs strong and free. How can I figure out where the problem is? Thanks, Paolo.
I have an 82 vanagon diesel too, but the heater fan is not working? also my fan on my rad is not working either? I will have the van running for even an hour and the fan by the rad doesnt even come on?? so about the heater fan motor, what fuse controls the heater fan in the van under the dash? thank you Roberto

poppat1203 Sat Jul 20, 2013 7:43 am

I got my'91 vanagon gl westy back from the mechanics after having the ac worked up. Before I took it in to the shop only the high speed fan was working. As the mechanic was explaining to me the work he did he mentioned that he had to "correct" some wiring issues in order for the rad fan to cycle on with the compressor. This didn't automatically spark my concern as the mechaninc made it sound as if he fixed something the previous owner did. But as I turned the ac on the high speed fan automatically kicked on with the compressor and my blinker fuse popped. I thought this to be peculiar and called him to see what exactly they had done to "correct" the problem with the fan. To my dismay, he informed me that they had to bypass the resistor (located behind the D's headlamp) because he "couldn't find the part." So I informed him of what I thought of this stunt (using language I wont reapeat) and told him that I would order the part and I expected him to remedy the situation, and that in the interim I would not use the ac. But yesterday as I was driving (without the ac on) the high speed fan kicked on, which is normal, and my blinkers fuse blew again and the fan cycled off,which again is normal. But, after a few minutes I started to smell faint smoke and I see smoke coming from my fuse pannel. Upon visual inspection, the 30 amp fuse is completely melted and has melted and warped the fuse pannel so bad that I cant get a new fuse in. So my question is this, what if any possible damage could this have done (other than my fuse pannel) to my radiator fan etc... And can anyone explain why my blinker fuse kept popping when the rad fan kicked on? I appologize for the long winded post but I think the back story was necessary. Needless to say, I wont be taking my van back these knuckle heads again.

T3 Pilot Sat Jul 20, 2013 7:54 am

I would take the Van to a qualified auto electrician, call BBB and mention that the mechanic who did the work almost burned your Van down
Tell the "mechanic" that you want your money back.(I know that he will refuse, but it would be fun to enrage him and see if you could get him to foam at the mouth.....)

You should probably check over all the work that they claim to have done on the Van; after all, if they treat your wiring like this, imagine what kind of shortcuts they took with the mechanical part of the job.....

This type of thing happened to me twenty years ago, and it is what prompted me to buy a set of tools and learn how to do it myself. Never looked back.

vandam Sat Jul 20, 2013 11:31 am

I say check the fan motor, it reminds me of when the defrost motor goes bad. It heats the control switch and melts but only in high speed cause no resistor. I am not familiar with the diesel system though. and maybe put the recommended fuse in the fuse box to prevent damage.

poppat1203 Sat Jul 20, 2013 1:19 pm

Syncro Pilot;

I will most definitely be filing a complaint with not only the BBB but, The California Bureau of Automotive Repairs as well.

I have also decided that I will try to do all future repairs that are within my capabilities. Between the Bentley manual and this website I think I'll be fine.

T3 Pilot Sat Jul 20, 2013 1:42 pm

Bad repairs that leave you stranded are one thing, but messing up the wiring, especially to the high speed fan which has a direct feed to the battery is downright dangerous.

After I calmed myself down, I recalled rewiring the crusty connectors when I replaced a Rad fan switch a while back. Not shown clearly in The Bentley, but there is a separate 50 amp fuse for the high speed fan just below the relay. Same area as the grounding "crowns" up behind your now melted fuse/relay panel.

Hey, good luck with the repairs

crazyvwvanman Sat Jul 20, 2013 1:51 pm

For your model van the high speed rad fan does not normally put a big draw on the 30 amp fuse because the high speed relay gets power from a separate power feed on a 50 amp fuse from the battery, not connected through the main fuse/relay panel. It sounds like the mechanic screwed up and made it so the high speed gets power from the weaker lower fan speed circuit.

Mark





poppat1203 wrote: I got my'91 vanagon gl westy back from the mechanics after having the ac worked up. Before I took it in to the shop only the high speed fan was working. As the mechanic was explaining to me the work he did he mentioned that he had to "correct" some wiring issues in order for the rad fan to cycle on with the compressor.....To my dismay, he informed me that they had to bypass the resistor (located behind the D's headlamp) because he "couldn't find the part." ..... after a few minutes I started to smell faint smoke and I see smoke coming from my fuse pannel. Upon visual inspection, the 30 amp fuse is completely melted and has melted and warped the fuse pannel so bad that I cant get a new fuse in. So my question is this, what if any possible damage could this have done (other than my fuse pannel) to my radiator fan etc... And can anyone explain why my blinker fuse kept popping when the rad fan kicked on? I appologize for the long winded post but I think the back story was necessary. Needless to say, I wont be taking my van back these knuckle heads again.

furrylittleotter Sat Jul 20, 2013 2:42 pm

The fuse should not get that hot at less than 15 amps period.

Like someone else said I suspect the fuse is not contacting properly. Try spinning it a dozen times to seat it and see if it stops. If not polish the contacts with emory cloth and try and seat it again.

DO NOT DRIVE THE VAN WITH THIS CONDITION.
A 250 degree fuse is not something you want to drive around with, unless you want to rewire your van.



What's up with the threadjacking?

Neil



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