HELP!! 79 f150 dash lights
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Junior User
Joined: Apr 2005
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HELP!! 79 f150 dash lights
My 79 is having an elecrical problem in my gauge cluster and I am stumped. It is mainly the left turn blinker light. When the headlights are off it works fine. If you turn them on, the left blinker light will stay on sometimes bright sometimes dim and the blinker will cycle very slow or not at all. What would cause something like this? Also the gauge lights on the far right of the cluster dont work. Changing the bulbs doesnt seem to help either. Any advice would be greatly appreciated.
Cargo Master
Joined: Aug 2003
Posts: 3,237
Likes: 3
From: Belleville, Ontario
How well do the left turn bulbs (front & rear) light up? Is one of them dull? Is there any difference with the left turn signal and the brake lights on at the same time? If so, go to the left taillight. Take the turn/park light fixtures out & make sure the ground to body connections are good & clean.
AL.
AL.
Cargo Master
Joined: Oct 2004
Posts: 2,148
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From: Seneca, SC
ok my 77 has the same problem so I'm gonna give you what I've already thought of. Haven't fixed it yet, but there's one of these problems in the turn signal circuit.
1.) the parking lights and turn signal are crossed at the bulb, this means that the turn signal will try to use the parking lights, which won't flash, or that they are intermittantly corssing, which means that the thing won't light at all. Change out the light housing.
2.) there's a ground messing up in the circuit, if any of your dash lights are messing up other than the turn signal, then this might be a problem. gonna have to chase this one down the old fashioned way, test light (or multimeter) and time.
3.) the flasher is worn out, this one's unlikely for me, but might not be for you.
Good luck, hope it helps, and if it was one of these things, then let me know and I'll try that one first. Sorry to guinea pig you like that, but right now the beater is busted and the rear axle needs swapped out in the truck, the turn signal's gotta take the back burner.
1.) the parking lights and turn signal are crossed at the bulb, this means that the turn signal will try to use the parking lights, which won't flash, or that they are intermittantly corssing, which means that the thing won't light at all. Change out the light housing.
2.) there's a ground messing up in the circuit, if any of your dash lights are messing up other than the turn signal, then this might be a problem. gonna have to chase this one down the old fashioned way, test light (or multimeter) and time.
3.) the flasher is worn out, this one's unlikely for me, but might not be for you.
Good luck, hope it helps, and if it was one of these things, then let me know and I'll try that one first. Sorry to guinea pig you like that, but right now the beater is busted and the rear axle needs swapped out in the truck, the turn signal's gotta take the back burner.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
Something in your headlight circuit is shorting into your turn signal.
I'm going to take a guess here, and suggest that one of the turn signal/parking light fixtures has a bad ground causing the parking light to feed back through the turn signal circuit. It could even be a dual filiment bulb where the filiment are touching. Take the lenses off and look at the bulbs with the parking lights turned on. If you see one of your turn signal filiments glowing, that's the bad fixture or bulb.
I suspect that the dash light problem is most likely right there in the cluster. Maybe the printed circuit.
I'm going to take a guess here, and suggest that one of the turn signal/parking light fixtures has a bad ground causing the parking light to feed back through the turn signal circuit. It could even be a dual filiment bulb where the filiment are touching. Take the lenses off and look at the bulbs with the parking lights turned on. If you see one of your turn signal filiments glowing, that's the bad fixture or bulb.
I suspect that the dash light problem is most likely right there in the cluster. Maybe the printed circuit.
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Junior User
Joined: Apr 2005
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OK, I removed the gauge cluster again and cleaned the all of the light connections. The lights on the right of the cluster work now. After work tomarrow I will inspect a few things and hopefully find my problem. I will let you guys know what happens. Thanks for the pointers.
Moderator
Joined: Jan 2001
Posts: 56,984
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From: Virginia
I can almost guarentee your blinker problem is with the left front marker/turn bulb out at the front of the truck. If you haven't got it fixed yet, take the left front marker/turn bulb out and clean up the connections in the socket and the brass part and connections on the bulb. That will probably fix it. If it doesn't, then I would follow the wires up from that socket and check for a broken or corroded ground wire.
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Ok, here is the update. I went out to work on the blinker problem after work today. The first thing I noticed was that the front drivers side blinker/running light is way dim compared to the passenger side. I removed what I think is the ground (on the radiator support) wire for the front blinker, to make sure the connection was clean; but the blinker still blinked even though the ground was removed. Is there another ground that I missed? When the front blinker bulb is in, with the blinker off, and you pull on the light switch, the blinker light in the dash will turn on and glow dim. However, I noticed that if I remove the blinker bulb in the front, you can trun on the light switch and the in-dash blinker light will not glow at all. SO, where should I look next? Thanks again for your help guys.
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Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
You are in the right spot. The parking light circuit is shorted into the blinker light circuit. It's probably corrosion, but if not it could be the bulb itself. Take a close look at the filiments to see if one filiment is touching the other. Or just take the bulb from the other side an plug it in there to see if it works.
Another possibility, it could be in the socket where the springs push the contacts out against the bulb.
Sounds like the mounting screws for the light housing are acting as the ground.
All this is assuming that you are using a 1034 or an 1157 type double filiment bulb.
Another possibility, it could be in the socket where the springs push the contacts out against the bulb.
Sounds like the mounting screws for the light housing are acting as the ground.
All this is assuming that you are using a 1034 or an 1157 type double filiment bulb.
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Moderator
Joined: Jan 2001
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From: Virginia
And it still can be a bad ground and corrosion in the socket like Bdox mentioned. You checked the radiator ground, but you didn't say if you cleaned the socket and the outside part of the bulb.
The parking light circuit current will run up backwards through the turn circuit if it can't find a good return path to ground. Running backwards up the turn circuit will cause the indicator to glow in the dash.
The parking light circuit current will run up backwards through the turn circuit if it can't find a good return path to ground. Running backwards up the turn circuit will cause the indicator to glow in the dash.
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