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electrical mystery 74.5 Gt

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electrical mystery 74.5 Gt
#1
  This topic is about my 1974 MG MGB GT
deadmansreef Avatar
deadmansreef Lawrence Barnett
FL, USA   USA
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1974 MG MGB GT
Tooling along this week and as i checked the gauges , fuel, temp and tach stopped working

I also noted turn and brake lites were NA

ALl fuses under the hood checked good. WOW what fun this is, Ideas.? Thanks

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Re: electrical mystery 74.5 Gt
#2
ex-tyke Avatar
ex-tyke Graham Creswick
Chatham, ON, Canada   CAN
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1976 MG MGB
Try using emery cloth/sandpaper on the fuse holder terminals - fuses are probably not making good contact with the spring clip/terminals...esp the third from the top..

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Re: electrical mystery 74.5 Gt
#3
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
Also the riveted contacts on the back of the fuse box become corroded and high resistance.

Herb


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Re: electrical mystery 74.5 Gt
#4
ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, AB, Canada   CAN
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1971 MG MGB
The voltage stabilizer would explain the fuel and temp gauges, but not the tach. If it was a bad fuse or connection on the green circuit then other green devices (such as the heater fan) would also be off.

I suspect there is a connector under the dash that splits the green power to the tach and voltage stabilizer that has corroded or come loose. Check all the green wire connections near the tach and voltage stabilizer.


Terry Ingoldsby
terry.ingoldsby@DCExperts.com

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Re: electrical mystery 74.5 Gt
#5
Wray Avatar
Wray Gold Member Wray Lemke
., SC, USA   USA
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1956 MG MGA
1958 MG Magnette ZB Varitone
1973 MG MGB
1974 MG MGB GT    & more
As noted above, the 3rd fuse down handles the green wire circuit that powers the gauges and the brake lights. The fuse holder is probably not making good contact. The same problem occurred on my 74.5 GT. Wiggling the fuse would make things work for a while. I replaced the fuse holder and cured it.

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Re: electrical mystery 74.5 Gt
#6
garyd Avatar
garyd Gold Member Gary Dabrowski
Naugatuck, western Connecticut, USA   USA
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1957 MG MGA 1500 "Long Gone"
1970 MG MGB GT
1974 MG MGB
1975 MG MGB
Lawrence;

I had the same problem with my 74' car. Yup, third fuse down was blown/not getting good contact.

A new replacement fuse box (my solution) would cure this or if you're handy you can polish the contacts and get by for a while.

Your car is 43 years old. I'll bet you a coffee that you have similar contact/corrosion issues perking away throughout the wiring harness where there are bullet connectors etc. Especially the grounds. FWIW, Before I put my 74 car on the road after purchasing it, I cleaned up all the grounds and replaced the female sides of all the bullet connectors along with polishing the bullets and intruducing a bit of dielectric greas to keep any future corrosion at bay. This done I have confidence that the harness will properly do its job while the car is under my stewardship. I learned this all the hard way operating my 75' car for four years.


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Re: electrical mystery 74.5 Gt
#7
mowog1 Avatar
mowog1 Gold Member Rick Ingram
Saint Joseph, IL, USA   USA
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1952 MG TD "Nigel"
1969 MG MGC "Vicky"
1972 MG MGB "Mallard"
1974 MG MGB GT V8 Conversion "The V8"    & more
I take off the fuse block and let it soak in some Muriatic Acid for a few minutes....remove...rinse and dry. Reinstall...apply some dielectric grease..takes care of most problems originating at the block.

In reply to # 3455936 by ex-tyke Try using emery cloth/sandpaper on the fuse holder terminals - fuses are probably not making good contact with the spring clip/terminals...esp the third from the top..


1952 MGTD - 1969 MGC - 1972 MGB - 1974&1/2 MGB/GT V8 conversion - 1978 MGB

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