70 Roadrunner Gauges and Fuse block problems

[Joeyms]

Good morning, I have a 70 Roadrunner with some new electrical issues. First, the gauges started acting up on a rally dash. Temp would run correct and then peg out. Same as oil pressure. Gas gauge worked fine. I changed out the voltage limiter, then the problems really started. Took the car out for a test drive and the three gauges went to half. The gas tank was full. After three miles all three gauges went dead. I checked the fuse box and have no power to the Accessory block, the heater block, and the instrument block. Checked with a test light from the back of the fuse box. No power coming in. I also have no instrument lights, ( bulbs are good). Headlights and taillights work, as does the dome light. Were do I look for the loss of electricity to the fuse box. Appreciate any help from you guys with the electrical knowledge.

Thanks

Joe
70 rr
71 Satellite
07 Dodge 1500

 

[mmissile]

These old dashes are junk. I've messed with mine for 2 years, and the problems keep changing. The fuel-level gauge is my worst head-ache. It worked when I got the car, quit, and now....after changing the sending unit and ground, it reads about 1/4 when it's over-flowing. My temp gauge will quit working for awhile...then work perfectly. I bypassed the amp gauge, altogether. The tach works fine, though LOL. The speedo gear in the trans is wrong, and reads fast. When I turn my parking lights on, both turn indicators light up.
The fuse-block was changed, completely. It had loose riveted connections, and was fairly grungy looking. That helped some of the initial electrical issues. If I cared enough, I'd order a whole,new dash harness for the car.

 

[Shorthorse]

I looked at the electrical drawing. Gauges and dash lights are separate form each other and a loss of power at the fuse box would make other non-dash things quit also. For instance, the heater switch is fed via the "switched" fuses while the dash lights are fed via "unswitched" power and are only fused after the light switch & dash dimmer switch and before the lights. It doesn't make sense.
When things don't make sense, look at grounds. I don't know whether the 70 dash grounds via a strap or mounting screws but it's a place to start.

http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerA.JPG
http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerB.JPG

 

[Joeyms]

I looked at the electrical drawing. Gauges and dash lights are separate form each other and a loss of power at the fuse box would make other non-dash things quit also. For instance, the heater switch is fed via the "switched" fuses while the dash lights are fed via "unswitched" power and are only fused after the light switch & dash dimmer switch and before the lights. It doesn't make sense.
When things don't make sense, look at grounds. I don't know whether the 70 dash grounds via a strap or mounting screws but it's a place to start.

http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerA.JPG
http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerB.JPG

Thanks,
the 70 dash grounds through the mounting screws. I need to look at it carefully.

 

[Joeyms]

I looked at the electrical drawing. Gauges and dash lights are separate form each other and a loss of power at the fuse box would make other non-dash things quit also. For instance, the heater switch is fed via the "switched" fuses while the dash lights are fed via "unswitched" power and are only fused after the light switch & dash dimmer switch and before the lights. It doesn't make sense.
When things don't make sense, look at grounds. I don't know whether the 70 dash grounds via a strap or mounting screws but it's a place to start.

http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerA.JPG
http://www.mymopar.com/downloads/1970/70BelvedereGTXSatelliteRoad RunnerB.JPG

Thanks for the diagram. I traced the wires from the cigar lighter, heater, ashtray light, and radio. I have a plug behind the fuse block that is short. I can't find it on the print. It has two yellow wires with tan tracer, red, blue with white tracer. Do you know what it plugs into?

 

[Shorthorse]

Thanks for the diagram. I traced the wires from the cigar lighter, heater, ashtray light, and radio. I have a plug behind the fuse block that is short. I can't find it on the print. It has two yellow wires with tan tracer, red, blue with white tracer. Do you know what it plugs into?

I believe that's the "key in" buzzer.

Here's another good link. you can get the entire service manual.
http://www.mymopar.com/index.php?pid=109

 

[Joeyms]

Thanks so much. The manual will be a big help. I need to find the other pigtail for it. Going to look now.

 

[Shorthorse]

I don't think there is another pigtail. That's where the buzzer plugs in.

 

[Joeyms]

I don't think there is another pigtail. That's where the buzzer plugs in.

View attachment 403492

That looks like the horn relay located under the dash on the left side of the steering wheel. I need to look for another one in the vicinity of the plug due to the length of the plug. That makes sense. The car is almost finished and I am just starting on instruments and electrical. I have had it for 15 years.

 

[Joeyms]

What is the part called?

 

[Shorthorse]

What is the part called?

Sorry, I just don't know enough about that year model. I have seen them on Ebay advertised as headlight/key warning buzzer, part number 4320085. Maybe someone on here will know the correct unit. Personally, I can't stand annoying warning buzzers.

 

[Joeyms]

Sorry, I just don't know enough about that year model. I have seen them on Ebay advertised as headlight/key warning buzzer, part number 4320085. Maybe someone on here will know the correct unit. Personally, I can't stand annoying warning buzzers.[/QUOTE

Found one on ebay along with a new headlight switch. I now have everything working except horn and windshield washer. Ordered a new horn relay on ebay also. The problem with the cluster lights is between the headlight swith and the dimmer. I will pull the dimmer out and clean it. Once I pull the cluster again, I will check the gauges with a six volt battery. Appreciate your help. I am starting to understand the electrical system now.