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Every lamp lights except backup lamps
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mustanger361
Novice
Nov 1, 2014, 5:56 AM
Post #1 of 11
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Every lamp lights except backup lamps
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2001 Dodge Cargo Van
Ram 2500
This is automatic transmission. Every lamp on the truck is operational except the backup lamps. The gear indicators in the dash light up and accurately show the gear selections. I have located the switch on the transmission. I removed the wiring harness, and the indicator lights went out, and came back on when I put the harness back on. But still no backup lights.
Is the switch bad? Seems like a no-brainer, but the fact that the dash indicator works makes me wonder. I don't want to buy a new one and still have no backup lights. I have seen, here in this forum, references to another switch in the circuit that could be a problem.
Also ... My old van is a carbon copy of this van. I pulled the switch out of the old van, thinking I would install it in the new van. I wasn't prepared for the transmission fluid to run out and make a mess. I see how the switch works now. I put it back in, and now there are no backup lights on the old van. Is there anything special to know about replacing this switch? Sure seems simple -- two screws.
This truck is in nice, clean, tight condition. It is a fleet truck.There has been no wire butchering or wire damage. 150,000 miles.
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Discretesignals
Ultimate Carjunky
/ Moderator
Nov 1, 2014, 6:42 AM
Post #2 of 11
(1770 views)
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Re: Every lamp lights except backup lamps
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There are three sets of contacts in the transmission range switch. One of the contacts is used to open and close the circuit for the reverse lamps. The other two are used by the powertrain control module and the instrument cluster gear indicator.
Using a volt meter back probe the range switch connector with the ignition on, you should have battery voltage on the white wire. You should also have voltage on the violet/black wire with the shifter in reverse. You have to make your voltage measurements with the circuit live. This means having the switch plugged in.
There shouldn't be anything to installing the range switch besides unscrewing and screwing it into the case.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 1, 2014, 6:51 AM)
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mustanger361
Novice
Nov 1, 2014, 6:58 AM
Post #3 of 11
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Re: Every lamp lights except backup lamps
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Having names for these components is really a big help. I will be back shortly.
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mustanger361
Novice
Nov 1, 2014, 9:02 AM
Post #4 of 11
(1751 views)
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Re: Every lamp lights except backup lamps
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OK, Discretesignals.
I tested for voltage with the harness attached, and with it not attached. I tested it with the transmission in park, and in reverse. I tested continuity on the individual pins on the switch, with harness removed. The only wire that has 12v is the one on the opposite end of the harness from the white wire. It appears to be black, maybe brown, with a yellow stripe. The white wire has no voltage. And of course the violet wire has no voltage. Can you tell me which wires do what? I did determine that the pins on the switch for the white and violet wires have continuity, with the transmission in reverse. The pin for the wire with voltage has no continuity with any other pin, in park or in reverse.
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Discretesignals
Ultimate Carjunky
/ Moderator
Nov 1, 2014, 10:09 AM
Post #5 of 11
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Re: Every lamp lights except backup lamps
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dark blue/white 5 volt supply from insturment cluster
black/white ground circuit back to instrument cluster
white power from fuse 12 (20 amp) with ignition on
violet/black circuit that goes to reverse lamps
brown/yellow power from coil side of starter relay with ignition in the start position
The brown/yellow wire is also sensed by the engine computer (PCM). When the switch is closed in the park or neutral position this will allow the starter relay to activate when you turn the ignition to start.
If you don't have power on the white wire with the ignition on, you need to check power at fuse 12 on both sides.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 1, 2014, 10:10 AM)
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mustanger361
Novice
Nov 1, 2014, 11:23 AM
Post #6 of 11
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Re: Every lamp lights except backup lamps
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OK. We are done with this phase. All good. The fuse was bad, although it looks good. I don't know if I would have figured out which fuse it is, although the "PRNDL" is a good clue. Should have proven the power first. Both trucks now have backup lights.
Is there a way to access automotive wiring diagrams?
Thanks a million for your help, or should I say thanks for saving me $60.00.
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Discretesignals
Ultimate Carjunky
/ Moderator
Nov 1, 2014, 12:21 PM
Post #8 of 11
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Re: Every lamp lights except backup lamps
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Your welcome.  Things happen for a reason. If the fuse is blown, you should inspect the wiring back there...especially if someone installed trailer wiring.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 1, 2014, 12:22 PM)
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mustanger361
Novice
Nov 2, 2014, 10:16 PM
Post #9 of 11
(1681 views)
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Re: Every lamp lights except backup lamps
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I know that's right. 20 is a stout fuse. The wiring is really pretty. No butchering or damage, no additions. Sometimes a fuse or breaker just trips or blows, looking for attention. And you don't find anything, and it doesn't happen again. If there is an actual problem, it will re-appear.
This truck has four stereo speakers. Three wouldn't work. I traced wires, tested, etc. Finally determined it was three bad speakers.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 3, 2014, 2:51 AM
Post #10 of 11
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Re: Every lamp lights except backup lamps
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You said fuse looked good? Rare but happens they just have a flaw? Truly blown should appear blown/burned but not always so checking for power on them is always best.
Now you said you found 3 or 4 speakers bad! Really. Has this vehicle been under water or something? That I find more unusual without some common cause,
T
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mustanger361
Novice
Nov 3, 2014, 4:48 AM
Post #11 of 11
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Re: Every lamp lights except backup lamps
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The truck is a clean machine, except for those hail dings. It's clean inside, outside, and underneath.
The fuse is the small blade type. It doesn't have a clear body. But I would still expect to see a black spot, some kind of indication. The meter showed no continuity. The spare worked fine. I just now put a strong light behind it. I saw a deformity at the bend, but couldn't really see daylight. Took it apart -- yes, it is melted. Now I want to know what is on that circuit beside two backup lamps.
The speakers -- I assumed that all three speakers couldn't be bad, so I didn't check them until all else failed. They are all identical. Original equipment. Two in the door, two in the cargo area. All three lost connection where the tiny wires from the coil connect to the flexible wire that leads to the terminals. The coils themselves were good. All three going bad seems like a factory defect. On the day they were built somebody had a hangover.
I am always astonished at how much wire is behind a dashboard.
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