[GMCnet] 25 amp fuse in place of 30?

[michael]

I have a problem with the compressor working then not. today we fired up the coach to run out and get some lunch and the pump ran for a bit then stopped. the level looked good so I figured it was good to go. coming back to the coach from lunch and I noticed that the rear was a bit low. I went to turn the coach on but the pump didnt even make a peep. I could not even manually raise it using the hold position. I looked at the fuse and there is a fuse that looks like this http://www.autozone.com/autozone/accessories/Duralast-20-Amp-at-12-VDC-clip-mounted-clip-mounted-circuit-breaker/_/N-2690?counter=7&filterByKeyWord=3ag+circuit+breaker&fromString=search&itemIdentifier=413282_0_0_

the fuse I have is rated for 25 but on the fuse block it says it needs a 30amp. does this matter? if not the fuse where can I look? i will have to take a picture of the compressor because I do not think it is original. It might be, but it doesnt say GMC on it.
--
1977 Palm beach
Bham AL
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[Charles Boyd]

Sir, that is a circuit breaker that resets itself. It should be a 30 amp. Do not use a glass fuse.


bronevaya wrote on Thu, 14 February 2013 15:19

> I have a problem with the compressor working then not. today we fired up the coach to run out and get some lunch and the pump ran for a bit then stopped. the level looked good so I figured it was good to go. coming back to the coach from lunch and I noticed that the rear was a bit low. I went to turn the coach on but the pump didnt even make a peep. I could not even manually raise it using the hold position. I looked at the fuse and there is a fuse that looks like this http://www.autozone.com/autozone/accessories/Duralast-20-Amp-at-12-VDC-clip-mounted-clip-mounted-circuit-breaker/_/N-2690?counter=7&filterByKeyWor d=3ag+circuit+breaker&fromString=search&itemIdentifier=413282_0_0_
>
> the fuse I have is rated for 25 but on the fuse block it says it needs a 30amp. does this matter? if not the fuse where can I look? i will have to take a picture of the compressor because I do not think it is original. It might be, but it doesnt say GMC on it.


--

C. Boyd
76 Crestmont
East Tennessee

[Richard Andis]

bronevaya wrote on Thu, 14 February 2013 14:19

> the fuse I have is rated for 25 but on the fuse block it says it needs a 30amp. does this matter? if not the fuse where can I look? i will have to take a picture of the compressor because I do not think it is original. It might be, but it doesnt say GMC on it.

The quick answer is that it's OK to use a fuse that's rated lower that what's supposed to be there but,...... unless it was a transient surge that blew the 30 amp, a 25 amp will have little chance of surviving. It's an emergency fix at best. Just avoid putting in a fuse rate HIGHER than what supposed to be there. That's when wires burn.


--
Walküre (1974 VW Thing) Future Toad,
Official GMC Motorhome Lurker and Coveter

[gene Fisher]

did you read this , and add the relay
http://www.gmcws.org/Tech/dsimmons/air_suspension/air-suspension-system.html

prob is just a supply problem
gene

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Sean Kidd]

I'm a licensed electrician, you size the wire to the load, you size the current limiting device (fuse or circuit breaker) to the wire at 125% factor . If you hav 20 amp load, depending on distance and temperature (voltage drop) 125%*20=25 amps, wire size chart says 10 AWG wire. #10 wire has a max ampere rating of 30 amps so use a maximum of 30A fuse. loose corroded terminals, wire length too far, or exposed to heat (above 90c) you need to increase wire size, then recalculate. this goes for ac or dc
--
73 Ex-Canyon Lands 26' #317 "Oliver"
Hubler 1-Ton, soon to have quadrareactiondisc rear.

[Thomas Phipps]

After seeing the Mickey mouse wire that the P.P.O. Installed in my current coach to the pump, I hard wired a relay in to carry the current needed for the air compressor plus ample oversized wire for the load. Used P.P.O.'s small gauge wire to trip a standard 12v automobile style relay. Pump runs much faster with heavier gauge wire. Cost was less than $10.
Dwayne's pamphlet was my inspiration.
Now, if I can just figure out what P.P.O. Did to the rest of the wiring.
Tom, MS II


--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20

[Steve Southworth]

SeanKidd wrote on Thu, 14 February 2013 16:35
> I'm a licensed electrician, you size the wire to the load, you size the current limiting device (fuse or circuit breaker) to the wire at 125% factor . If you have 20 amp load, depending on distance and temperature (voltage drop) 125%*20=25 amps, wire size chart says 10 AWG wire. #10 wire has a max ampere rating of 30 amps so use a maximum of 30A fuse. loose corroded terminals, wire length too far, or exposed to heat (above 90c) you need to increase wire size, then recalculate. this goes for ac or dc


Well those ratings are for premises wiring per NFPA/NEC. Those ratings do not apply to SAE applications at 12VDC. For instance on my '74 GMC the #10 wire to the house panel is breakered at 50 amps. My compressor also is marked for 30A but has a 25A breaker installed.

Ancor wiring has information on 12VDC ratings here:

http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&page=Marine-Wire

Note that they list a #10 AWG as good for up to 60 amps. As per NEC, FPN's do apply.

All that being said, using NEC ratings will give you a safe and very well functioning 12VDC electrical system.


--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

[John R. Lebetski]

If anyone finds a source for GM 30a breakers that fit the fuse holder, let me know. I have been using 30a fuses as I can't find the breaker with the round connector ends. Thought it would be easy as GM used that style in power window circuits for many years. The fuses don't last too long before needing replacement.
--
John Lebetski
Chicago, IL
77 Eleganza II
Source America First

[Thomas Phipps]

Just buy the readily available breaker at the auto parts store. Cut out the fuse holder, apply eyelets to the wire ends, attach breaker and be done with it.

Tom, MS II
--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20

[Mike]

JohnL455 wrote on Sat, 16 February 2013 15:58

> If anyone finds a source for GM 30a breakers that fit the fuse holder, let me know. I have been using 30a fuses as I can't find the breaker with the round connector ends. Thought it would be easy as GM used that style in power window circuits for many years. The fuses don't last too long before needing replacement.

Try Advance Auto:

http://shop.advanceautoparts.com/buy/products/204953-30-amp-circuit-breaker-fuse-clip-glass-by-dorman-conduct-tite-part-85617-relays.html#
--
Mike K.
'75 PB
Southeast Michigan

[Thomas Phipps]

On my GMC, the fuse to the air compressor has an in-line fuse holder. The Dotman will not install inside the connector. I'm not sure that you would ba able to keep it connected, or protected from the elements. JMO

Tom, MS II
--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20

[Steve Southworth]

JohnL455 wrote on Sat, 16 February 2013 14:58

> If anyone finds a source for GM 30a breakers that fit the fuse holder, let me know. I have been using 30a fuses as I can't find the breaker with the round connector ends. Thought it would be easy as GM used that style in power window circuits for many years. The fuses don't last too long before needing replacement.

Waytek Wire:

http://www.waytekwire.com/products/1366/Circuit-Breakers/&Type=Glass-Fuse-Style

I recently ordered some. Their delivery almost matches McMaster-Carr. I believe they are available in better auto parts stores also.

--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

[Robert Mueller]

Steve,

Great find!

Tom Hampton put one of those in Double Trouble when we were troubleshooting a circuit that kept blowing fuses. He noted that it
wasn't a good idea to do that and NOT fix the problem.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

 
-----Original Message-----
From: Steve Southworth

JohnL455 wrote on Sat, 16 February 2013 14:58
> If anyone finds a source for GM 30a breakers that fit the fuse holder, let me know. I have been using 30a fuses as I can't find
the breaker with the round connector ends. Thought it would be easy as GM used that style in power window circuits for many years.
The fuses don't last too long before needing replacement.

Waytek Wire:

http://www.waytekwire.com/products/1366/Circuit-Breakers/&Type=Glass-Fuse-Style

I recently ordered some. Their delivery almost matches McMaster-Carr. I believe they are available in better auto parts stores
also.
--
Steve

[D C _Mac_ Macdonald]

If the fuse-blowing problem is a result of "surge"
you may wish to go to "Slow-Blow" type fuses!

Which circuit is causing you the grief?

As Rob said, however, if GMC said to use 25A fuses
and the 30A blow, you definitely have a problem
that needs to be located and corrected!

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*

[John Wright]

John,
Here is another source for the 30 amp snap in circuit breaker. You should also check the load on that circuit.

http://tinyurl.com/ado8euo

J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan