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All kinds of instrument problems!

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1.1K views 9 replies 7 participants last post by  KThaxton  
V
#1 ·
I'm having all kinds of instrument problems!

I took my '78 RC out for a run yesterday. Out of the blue I caught a whiff of smoke . . . .wire smoke! I was right down the road so I made it back to the driveway before smoke actually started rolling pretty good out of the hole where my tach should be and filling up inside the gauge faces. I popped the bezel to see that the positive lead, where it attaches to the Alt meter behind the instrument cluster, was smoldering and melting the housing as well as some pretty important parts of both the Alt gauge and the Fuel gauge. As I disconnected the wire bundle and the positive and negative leads and started to remove the instrument cluster the speedo cable somehow became hooked on the bottom of the cluster. Not knowing the cable was hooked, and being slightly ( if irrationally ) pissed at the truck, I proceeded with slightly more power than necessary. This disconnected the bottom end of the core or the speedo cable and left it freely moving in the cable housing. I had a few backup clusters so I was able to cannibalize them and make one good Frankenstein cluster using housings, circuit boards, and gauges from the bunch. Everything seems to work accept . . . . .

The Alt meter is pinned on charging when ever the truck is running. It seems to read correctly when the ignition switch is turned on, but ass soon as the motor turns over "C". What do you think . . . .bad gauge or something else screwed up?

No Speedo. Where is the bottom end of the cable? Is that it going into the "box" on the transfer case? What is involved in hooking it back up?

The tach has two leads coming off of it. Where are they supposed to go?

Thanks in advance for any help!
-Sam
 
W
#2 ·
I would read this with respect to your ammeter:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml

As for your speedo, unless you have cruise, the cable should screw into the reduction box on your transfer case. Tach hook up is usually one to ground (typically black), one to - (neg) side of coil (typically green). Factory or aftermarket tach? Hope this helps.
william
 
V
#3 ·
Thanks!

The article helped . . . if just to let me know I'm not alone . . .LOL

I'm checking the speedo cable.

I assume the tach is aftermarket. I bought the truck last year and it was just stuck in the dash unwired!

-Sam
 
V
#4 ·
OK . . . .
I have the speedo hooked back up the way I thought was correct. It works like a champ between 0 and about 40MPH. Then it jumps right to 65-70 and dances up between them until I come to a stop. After the full stop, it repeats the same behavior. Where'd I screw the pooch?
-Sam
 
#5 ·
Might be a bad speedo or one of the ends of the cable is messed up or the cable has a kink in it.
My 83 RC had a speedo that bounced around once I got up over about 40 mph. I replaced it with a junkyard model and it cured the problem.
 
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V
#7 ·
OK . . .. back to the amp-meter . . .

According to that article, the direct connection to the meter is a basic design flaw. What is the remedy short of rewiring the dash ( which is an endevor that might be beyond my present abilities . . lol ) ? Bypass the meter? If so, is there a better way to reconnect the amp meter?

-Sam
 
G
#8 ·
You can bypass the meter by just connecting the two wires of the ammeter together. Make sure that it is a solid connection if you do that, since all the power for your vehicle is running through those two wires. If at all possible, find a friend that will solder and heat shrink the wires together for you, if you aren't able to do it yourself. It's not like the rewiring that they recommend in the article, as it still leaves the blade connections intact at the bulkhead connector, but it's a pretty simple fix.
 
C
#9 ·
Shorting out the meter wont solve the problem.
The basic problem is that the entire current for the electricals goes in and out of the cab via the multipoint connector. Thats a lot of current for the connector contacts.
You want to make the splice before that connector.
That MAD electric site gives you exact instructions regarding "why" and "how". Read the information on that site carefully and understand the concept first. Then you will understand what you are doing and why you are doing it.
 
#10 ·
Catsavvy said:
Shorting out the meter wont solve the problem.
The basic problem is that the entire current for the electricals goes in and out of the cab via the multipoint connector. Thats a lot of current for the connector contacts.
You want to make the splice before that connector.
That MAD electric site gives you exact instructions regarding "why" and "how". Read the information on that site carefully and understand the concept first. Then you will understand what you are doing and why you are doing it.
Click to expand...
Agreed.
The ammeter connection is only half of the problem with that set-up. It will only be a matter of time before you have meltdown at the firewall connection too.
 
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