secondary) tank?
Dash lights not working?
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Dash lights not working?
I have a 1978 f150 supercab 400 ranger. We bought it recently for $1400 in good condition with not much rust. 119k miles. But we have some minor problems with it. The speedometer is not working ( getting new part, a piece that was holding it onto the dash broke off). Here is the first problem i don't understand. 1. the dash lights are NOT working and every light besides them is working, also the fuel gauge, oil gauge and every gauge besides the battery gauge is not working. What do you think could be wrong? I took of the dash and checked the plug in to the dash with a test light and some were not getting any power. Could it be bad grounds or the headlight switch? Problem #2 is that the aux tank(secondary tank) is not working and not delivering any gas to the engine. Could it be the switch or something else? I checked under the truck where it switches between the pumps and it was not getting any power. another ground problem? Please respond as soon as possible. I have already ordered a speedometer cable and new headlight switch.(Cheap). 
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
It's easily replaced, pretty much "plug-n-play"...
Most any parts store should have it for around 50 bucks.
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MSEE
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From: Austin, TX
Be exact in your description of the problem and steps taken to troubleshoot the problem. I should be able to replicate your experiments to a tee on my own truck without having to ask you any questions.
The quality and expedience of the help you receive on this forum depends directly on you, your level of detail, and commitment to providing the information that's requested.
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Bought new part. put it on there with some dielectric grease. Fuel gauge, oil gauge, and temperature gauge are still not working. Blinkers are working. Dash lights are not. We have all the dash lights in. Fasten belts light also works.
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Posting Guru
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From: Burlington, WI
The speedo sounds like it needs a new cable. I think you said you bought a new one, which is good.
The oil gauge is usually broken on most trucks...for some reason not mine though and I don't know why they stop working.
The gas gauge is the same thing as the oil gauge. I think the sending unit may be bad in your tank but don't hold me to that one.
As for the dashlights, I bought my truck the same way. Blinkers worked, bulb that illuminates the "wiper" and "headlights" region worked, brake warning light and seatbelt light worked, etc. Turns out that my bulb holders weren't making good contact with the printed flexible circuit board because my plastic dash was crumbling away and let the bulbs fall out. So I replaced all the bulbs and soldered the bulb holder contacts to the copper on the board with small gauge wire and what do you know...all my dashlights began to work.
long story short, check you connections in the dash itself and try replacing the bulbs if you haven't already. Also check your fuses....always and i mean ALWAYS start problem diagnosis by checking fuses. In the cases of old cars like this I usually just replace all the fuses as soon as I buy the car. Saves time down the road
The oil gauge is usually broken on most trucks...for some reason not mine though and I don't know why they stop working.
The gas gauge is the same thing as the oil gauge. I think the sending unit may be bad in your tank but don't hold me to that one.
As for the dashlights, I bought my truck the same way. Blinkers worked, bulb that illuminates the "wiper" and "headlights" region worked, brake warning light and seatbelt light worked, etc. Turns out that my bulb holders weren't making good contact with the printed flexible circuit board because my plastic dash was crumbling away and let the bulbs fall out. So I replaced all the bulbs and soldered the bulb holder contacts to the copper on the board with small gauge wire and what do you know...all my dashlights began to work.
long story short, check you connections in the dash itself and try replacing the bulbs if you haven't already. Also check your fuses....always and i mean ALWAYS start problem diagnosis by checking fuses. In the cases of old cars like this I usually just replace all the fuses as soon as I buy the car. Saves time down the road
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Had the same problem with the dash lights in my truck, pulled the whole cluster out - totally dry rotted and crumbly. No way the printed circuit board was making good contacts. I found a replacement cluster in the local salvage yard out of an 80's conversion van, matched right up no problem. Cheap too. I'd recommend doing the same, try finding an 80s Econoline, preferably conversion (people seem to take better care of them), in your local wrecking yard and pull the instrument cluster. If you're lucky the yard won't charge you for all the gauges. I got the works for around $25. Ended up replacing a couple of the gauges that were malfunctioning while I was at it. But if they want to charge you an arm and a leg for the works the cluster is modular so you can remove the gauges and just buy the housing with the attached circuit board.
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Yes, i bought a new dash cluster, went to a salvage yard had a 77(i believe) like in brand new condition cluster! back looked complete and nice, no wear and look like they never removed it from the truck! 
but we put it in the dash and the lights worked completely fine.
but we put it in the dash and the lights worked completely fine.
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From: Simi Valley, CA
1975/79 F100/350 - 1975/80 Econoline - 1978/79 Bronco:
The instrument cluster backs were made of a composition material that can TURN TO DUST before your very eyes!
1981: FoMoCo began installing hard plastic cluster backs in Econolines, were the "service part replacements" for the POS cluster backs.
Some of the POS have been replaced with hard plastic cluster backs, some have not.
E1PZ-10848-A .. Hard Plastic Cluster Back-Use with Oil/Amp GAUGES / 1981/91 Econoline, retrofit: 1975/79 F100/350, 1975/80 Econoline, 1978/79 Bronco.
E1PZ-10848-B .. Hard Plastic Cluster Back-Use with Oil/Amp WARNING LAMPS / 1981/86 Econoline, retrofit: same applications as above.
CARPENTER NOS OBSOLETE PARTS in Concord NC has dozens of each = 800-476-9653.
The instrument cluster backs were made of a composition material that can TURN TO DUST before your very eyes!
1981: FoMoCo began installing hard plastic cluster backs in Econolines, were the "service part replacements" for the POS cluster backs.
Some of the POS have been replaced with hard plastic cluster backs, some have not.
E1PZ-10848-A .. Hard Plastic Cluster Back-Use with Oil/Amp GAUGES / 1981/91 Econoline, retrofit: 1975/79 F100/350, 1975/80 Econoline, 1978/79 Bronco.
E1PZ-10848-B .. Hard Plastic Cluster Back-Use with Oil/Amp WARNING LAMPS / 1981/86 Econoline, retrofit: same applications as above.
CARPENTER NOS OBSOLETE PARTS in Concord NC has dozens of each = 800-476-9653.
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