1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Main relay?

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Old 02-19-09, 07:24 PM
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Unhappy Main relay?

Ok i have a 1985 Mazda rx7 GSL_SE and i was coming from lunch today and i nearly got tboned by a car so i ended up sliding sideways and then bringing the car back in control. all of a sudden about 5 seconds later i see all of my dummy lights come on and looks like my radio shorted out./melting. i cut the car off and coast back into work and. i unplug the radio and it smells horrible. i check the lower fuses by the kick panel and about 3 of those where blown. I go to try and start the car back up and it does nothing at all. even the clock doesnt come on. no power what so ever. Im trying to find out where the main relay is on my car so i can replace it asap! I searched and saw people converting to the 2cnd gen fuse box. but i just need to know exactly what im looking at. i see those fuseable links but not sure how to tell if there bad. can anyone please send some pics and knowledge?!!

Thanks
Old 02-19-09, 08:43 PM
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Fusible links are wire covered with a cloth sleeve and a terminal on each end. If they are blown the wire will be burned through. It should be easy to see. I would be real sure your battery didn't shift and short against the body. The fusible link that would cause what you describe (nothing when ignition is turned on) is the middle of the group of three labeled Main. Sounds like a wire behind the radio shorted to ground. Were there any visible melted wires? These are the main relays (black circular relays).


Old 02-19-09, 11:02 PM
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how often do those main relays go bad? i replaced the fusable links with wire,fuses. i got power to my headlights but when i try to put the key in the ignition and start it up. all of the power just dies out. so i will check the battery tomm i guess and redo some links
Old 02-19-09, 11:45 PM
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i've never had a main relay give up the ghost.. definatly check the battery cables. make sure they're secure and clean.
Old 02-20-09, 03:25 AM
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Battery Hold Down Hardware

Is your battery tied down properly? 56-030A-FA54 70-985B-0370
Old 02-20-09, 06:03 AM
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You can use the same fuses that a 2nd gen uses to replace the fusible links. Little snug, but they will fit into the 1st gen link box. Factory link values are 45 amps (I use 50) for the main and 20 amps for the others. I have pictures somewhere here of mine. Never seen a bad main relay either. Seems likely something was thrown around when you had your idiot avoidance moment. Somewhere a 12v wire or terminal was pushed against the body or some other ground point. If smoke and smell came from behind the radio, I'd start looking around there. I've had a not stock height battery shift and the + terminal come in contact with the hood hinge. As I drove around the battery terminal continuously bumped against the hood trying to weld itself there permanently. I found it easily after a couple days. I opened the hood and there was a 6" diameter burn mark on the hood.
Which three fuses blew in the fuse block and which fusible links were bad?

Ron
Old 02-20-09, 07:15 AM
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the 3 that looked bad where from the main box. the (brown,black,brown) wish me luck as i have to ride to work in 25 degree weather on my R1!!
Old 02-20-09, 09:19 AM
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^^^that definatly sucks... keep us updated on what you find
Old 02-20-09, 09:22 AM
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It would be a good idea to locate the source of the short before you go replacing the links/fuses/relay. Otherwise, you've got a good chance of just blowing them all again.

Replacing a fusible link with wire = burning up a lot of more expensive stuff should a short occur.

I don't know the wiring of an 85 that intimately, but one of the worst short points inside the SA console is the cigarette lighter connection - very poorly designed connection, prone to shorts if anything metal should fall down inside there, and as it's designed to provide high current, it can make quite a mess.
Old 02-20-09, 11:53 AM
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I will check the cigarette lighter area then. i really think it was my radio some how. its all burnish smelling inside the cd player.
Old 02-20-09, 01:59 PM
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The radio should be on a pretty lightly-fused line... but if it was an aftermarket install by 'others', sometimes they will take nasty shortcuts in the wiring install, and you'll end up on a high-current hot line or something. Then if the radio shorts, it causes 'collateral damage.'
Old 02-20-09, 03:19 PM
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thats exactly what happened i think it was wired kinda ganky for what i can see. something happen somewhere for it to be smelling like it does. im gonna work on it when i get home. will the car even start if i put like a 50 amp inline fuse to the main even though it needs 60?
Old 02-20-09, 06:33 PM
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There are three wires leaving the fusible link box. Main (middle) is a larger gauge White/red. It goes to the back of the fuse box. The smaller gauge White/red goes directly to the headlight motors and the smaller gauge White/green goes directly to the combination switch and the retractor switch on the dash. If all three of the links blew at once seems like something would have to ground all three. They run together from the fusible link box down in front of the strut tower. The small White/red wire splits off after 12" or so. It runs forward towards the radiator while the other two run back to the firewall. Were all three links burnt in half?

Stock links are 45 amp and 20 amp. I'll post some pics of the fuses you can use when my son gets back with the car.
Old 02-20-09, 06:53 PM
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I replace the stock wire links with Bussman Fusible link. 50 amp PN is FLF-50.
Attached Thumbnails Main relay?-link.jpg   Main relay?-fusiblelinks.jpg  
Old 02-20-09, 09:34 PM
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i had that happen a while back, but it was just the negative battery cable came loose after i turned... it was really loose.
Old 02-21-09, 11:00 AM
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ok so i went out and bought some huge bus 60,40 amp fuses. i didnt end up with the one that74 rx4 had cause they where out of stock. so i ran some new wires with the bus fuses in the line to see if it would start. well it did and the whole time the key was in the starting position i had an annoying beep going on. the car started up and my battery gauge goes nuts and the tach does not work but it looks like my gas gauge worked. i go to rev it up a tad and it pops the wire off of the 60 amp. what would make my tach not work? i will be pulling out the cluster in a few. waiting on a friend to drop off a 2cnd gen fuse box. can anyone tell me if the bussman fuse that 74 rx7 has pictured will just fit into the connectors?
Old 02-21-09, 03:58 PM
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alright well i swapped the ignitors around cause i figured my trailing one was bad since the tach doesnt work and for some reason my buzzer goes off. the car starts up and still no tach. the battery gauge shoots up to about 16v when i rev it up. the alternator is only about 2 weeks old. What in the hell is going on with my car?
Old 02-21-09, 05:11 PM
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Those fuses should fit into the 1st gen link box. I'm assuming the buzzer is the key reminder buzzer. Didn't you have an issue with your ignition switch? There is some type of micro switch in the ignition switch that triggers the buzzer. You might want to try jamming the key in and out a couple times.
Old 02-21-09, 05:54 PM
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thanks, well im on the theory that my alternator might have something to do with all of this blowing up. its a old mazda glc alternator on it. previous owner put it on my car and it went out. so i went to replace it and i couldnt figure out why the one they where giving me wouldnt bolt up or even look the same. only later to find out the previous guy had the glc alternator on this car( the one with the fans on the outside) I noticed when i started the car today that my battery gauge went up to 16 volts. so either the voltage reg. is bad in the alternator or my whole gauge cluster is just shot. an 85 alternator is on order so i will know by tuesday!
Old 02-23-09, 07:23 PM
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Car is back up and running. THanks!
Old 02-24-09, 08:13 AM
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what problem did you find?
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