my 85PU no backup lights

nomiss05 · 08-03-2008, 10:57 PM

i have a 85PU but my backup lights dont work. brake, blinker and running lights are fine. i am wondering where the short probably is, i found that the red wire is my reverse light but i dont see open wire when i trace is. since its both lights i figure its a short in the main line before it splits. can anyone give me some suggestions to finding it, or maybe where it starts to see if it pulled out or anything. also any fuse relating to lights is fine.

4Crawler · 08-04-2008, 08:20 AM

Check the reverse light switch in the transmission if you have not already done so. Where is it? Usually driver's side of the transmission, down by the oil fill plug. Or in short, the only thing with wires attached to it on the transmission.

nomiss05 · 08-04-2008, 09:59 AM

sweet man thanks. i woulda never looked there, if its bad how can i replace it? is it an easy fix or something to just take into a shop and let them do? also how do i disable that dang buzzer, people talk about doing it but i dunno what they did... disable the actualy pressure switch or just find the buzzer and cut the wires?

4Crawler · 08-04-2008, 10:06 AM

Well if you think about it, where is reverse gear located? In the transmission, thus that is where the switch needs to be. I think the switch just screws into the transmission housing, so easy to replace if needed.

Not sure what buzzer you are referring to.

nomiss05 · 08-04-2008, 10:20 AM

that makes complete sense.. i appriciate it.. nice thing is since iv done a good job rebuilding this truck and putting money into it my parents are going to let me bring my second truck home to start rebuilding in my back yard

nomiss05 · 08-04-2008, 12:09 PM

so i pulled the switch apart, the wires are fine on both sides so there is no short there, i used a voltage tester on the switch coming out of the transmition.. i had nothing, so does that mean that its bad and i need a new one? or would there be no voltage coming from it anyway? i did it in and out of reverse and still had nothing..

4Crawler · 08-04-2008, 12:17 PM

A voltage tester will show you nothing at the switch. Why? It is just a contact that opens and closes. You would want to use an ohm meter (resistance) or battery powered test light to see if there is continuity inside the switch contacts while in reverse (and no continuity when in any other gear).
http://www.4crawler.com/4x4/CheapTri...oUseAnOhmMeter

nomiss05 · 08-04-2008, 01:20 PM

okay i am getting a reading with it while in reverse and not in any other gear.. so if the swich is okay whats the next plan to go to?

4Crawler · 08-04-2008, 01:25 PM

Switch sends power to the backup lights. The switch may give you a reading on a meter (micro-amps of current) but it may not flow enough current to light the light bulbs (several amps of current). Or the 12 volt source at the plug may be bad. So check the connector for 12 volts (one pin should be hot). Then try a jumper wire in the lug to tie the two pins together like the switch would do. If none of that works, check voltage and ground connections at the bulb sockets. If still problems, trace the wiring looking for an open or short circuit.

nomiss05 · 08-04-2008, 01:32 PM

im going to replace the switch just because its old and then ill see if they work after that, if not then ill look at the plug. if the swtch is bad then i wouldnt get the 12 volts at the bulb connector anyways right? so i kinda have to make sure the switch is working 100% before i can narrow down other possibilities..

4Crawler · 08-04-2008, 01:38 PM

Easy check of the switch is to plug in a jumper wire into the plug connecting the two pins the contact together. How to make a jumper wire? Take a paper clip or piece of wire and bend into a "U" shape and shove it into the plug making contact with both pins, something like this:

If backup lights light, switch is bad. If not, something else is the problem.

nomiss05 · 08-04-2008, 01:40 PM

sorry if i sound ignorant, but the u shaped wire is going to go into the plug that comes down, not the one thats connected into the trans right?

4Crawler · 08-04-2008, 01:44 PM

Quote:

Originally Posted by nomiss05

sorry if i sound ignorant, but the u shaped wire is going to go into the plug that comes down, not the one thats connected into the trans right?

You have the switch screwed into the transmission. Then you have the connector that plugs into the switch and is what has wires connected to it. Unplug the connector and shove a jumper wire into the connector that you just unplugged. What you want to do is connect the one pin in that connector that has 12 volts on it to the other pin that that sends power to the backup lights.

nomiss05 · 08-04-2008, 01:53 PM

okay i made the wire from the plug that comes from the truck and made the u into its self and god nothing, so i guess its not the switch

4Crawler · 08-04-2008, 01:59 PM

Well in that case, you take the "divide and conquer" approach. You are currently about in the middle of that circuit. You need to find out if you have a solid 12 volts at that plug. If so, then the problem lies between that plug and the backup lights. If you do not have 12 volts at that plug, then the problem lies between the plug and the battery:
- http://www.4crawler.com/4x4/CheapTri...leshootingTips

nomiss05 · 08-04-2008, 02:01 PM

i can just use my normal voltage tester on the plug side like i did on the ohm tester on the switch side? do i need to have it in reverse to test and see if it has 12 volts?

4Crawler · 08-04-2008, 02:09 PM

To measure voltage you use a volt meter voltage tester). To test resistance you use an ohm meter. So to test voltage, set meter to volts and check the pins. Note there is no ground in that connector, so put the black probe on some bare steel of the frame and the red probe on the connector pin. One should be hot (i.e. reads 12 volts with the ignition on) and one is not hot (i.e. has no voltage).

nomiss05 · 08-04-2008, 02:15 PM

i dont have 12 v to that plug, so now comes the fantastice world of fallowing wires and hoping to see a short...

nomiss05 · 08-04-2008, 02:35 PM

okay so where does the wire start to trace it from the start to the plug? i figure ill just keep testing it every so often to see if i have 12 v still and ill narrow down my short location

4Crawler · 08-04-2008, 03:43 PM

A Factory Service Manual will have the wiring diagram in it with wire colors, etc. There are PDF versions on-line that you can down load. That power comes from the ENGINE fuse circuit, then runs to the switch and back to the lights. You can follow the wires from the transmission up to the main wiring harness up in the engine.

And unless you have blown fuses, you are probably not looking for a short circuit. Rather it would be an open circuit (i.e. a broken wire or bad connection some place) that is preventing current from flowing.

nomiss05 · 08-04-2008, 04:15 PM

found the problem.. whoever owned the truck before me had a while plug thats just above the starter plugged into a green plug.. once i plugged the two while backs back tgether.. perfect.. now if only i knew what the green plug went to

08-03-2008, 10:57 PM	#1 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	my 85PU no backup lights i have a 85PU but my backup lights dont work. brake, blinker and running lights are fine. i am wondering where the short probably is, i found that the red wire is my reverse light but i dont see open wire when i trace is. since its both lights i figure its a short in the main line before it splits. can anyone give me some suggestions to finding it, or maybe where it starts to see if it pulled out or anything. also any fuse relating to lights is fine.

08-04-2008, 08:20 AM	#2 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	Check the reverse light switch in the transmission if you have not already done so. Where is it? Usually driver's side of the transmission, down by the oil fill plug. Or in short, the only thing with wires attached to it on the transmission. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 10:06 AM	#4 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	Well if you think about it, where is reverse gear located? In the transmission, thus that is where the switch needs to be. I think the switch just screws into the transmission housing, so easy to replace if needed. Not sure what buzzer you are referring to. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 12:17 PM	#7 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	A voltage tester will show you nothing at the switch. Why? It is just a contact that opens and closes. You would want to use an ohm meter (resistance) or battery powered test light to see if there is continuity inside the switch contacts while in reverse (and no continuity when in any other gear). http://www.4crawler.com/4x4/CheapTri...oUseAnOhmMeter __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 01:25 PM	#9 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	Switch sends power to the backup lights. The switch may give you a reading on a meter (micro-amps of current) but it may not flow enough current to light the light bulbs (several amps of current). Or the 12 volt source at the plug may be bad. So check the connector for 12 volts (one pin should be hot). Then try a jumper wire in the lug to tie the two pins together like the switch would do. If none of that works, check voltage and ground connections at the bulb sockets. If still problems, trace the wiring looking for an open or short circuit. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 09:59 AM	#3 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	sweet man thanks. i woulda never looked there, if its bad how can i replace it? is it an easy fix or something to just take into a shop and let them do? also how do i disable that dang buzzer, people talk about doing it but i dunno what they did... disable the actualy pressure switch or just find the buzzer and cut the wires?

08-04-2008, 10:20 AM	#5 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	that makes complete sense.. i appriciate it.. nice thing is since iv done a good job rebuilding this truck and putting money into it my parents are going to let me bring my second truck home to start rebuilding in my back yard

08-04-2008, 12:09 PM	#6 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	so i pulled the switch apart, the wires are fine on both sides so there is no short there, i used a voltage tester on the switch coming out of the transmition.. i had nothing, so does that mean that its bad and i need a new one? or would there be no voltage coming from it anyway? i did it in and out of reverse and still had nothing..

08-04-2008, 01:20 PM	#8 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	okay i am getting a reading with it while in reverse and not in any other gear.. so if the swich is okay whats the next plan to go to?

08-04-2008, 01:32 PM	#10 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	im going to replace the switch just because its old and then ill see if they work after that, if not then ill look at the plug. if the swtch is bad then i wouldnt get the 12 volts at the bulb connector anyways right? so i kinda have to make sure the switch is working 100% before i can narrow down other possibilities..

08-04-2008, 01:38 PM	#11 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	Easy check of the switch is to plug in a jumper wire into the plug connecting the two pins the contact together. How to make a jumper wire? Take a paper clip or piece of wire and bend into a "U" shape and shove it into the plug making contact with both pins, something like this: If backup lights light, switch is bad. If not, something else is the problem. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 01:40 PM	#12 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	sorry if i sound ignorant, but the u shaped wire is going to go into the plug that comes down, not the one thats connected into the trans right?

08-04-2008, 01:53 PM	#14 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	okay i made the wire from the plug that comes from the truck and made the u into its self and god nothing, so i guess its not the switch

08-04-2008, 01:59 PM	#15 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	Well in that case, you take the "divide and conquer" approach. You are currently about in the middle of that circuit. You need to find out if you have a solid 12 volts at that plug. If so, then the problem lies between that plug and the backup lights. If you do not have 12 volts at that plug, then the problem lies between the plug and the battery: - http://www.4crawler.com/4x4/CheapTri...leshootingTips __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 02:01 PM	#16 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	i can just use my normal voltage tester on the plug side like i did on the ohm tester on the switch side? do i need to have it in reverse to test and see if it has 12 volts? Last edited by nomiss05 : 08-04-2008 at 02:02 PM.

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08-04-2008, 02:09 PM	#17 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	To measure voltage you use a volt meter voltage tester). To test resistance you use an ohm meter. So to test voltage, set meter to volts and check the pins. Note there is no ground in that connector, so put the black probe on some bare steel of the frame and the red probe on the connector pin. One should be hot (i.e. reads 12 volts with the ignition on) and one is not hot (i.e. has no voltage). __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 02:15 PM	#18 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	i dont have 12 v to that plug, so now comes the fantastice world of fallowing wires and hoping to see a short...

08-04-2008, 02:35 PM	#19 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	okay so where does the wire start to trace it from the start to the plug? i figure ill just keep testing it every so often to see if i have 12 v still and ill narrow down my short location

08-04-2008, 03:43 PM	#20 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,261	A Factory Service Manual will have the wiring diagram in it with wire colors, etc. There are PDF versions on-line that you can down load. That power comes from the ENGINE fuse circuit, then runs to the switch and back to the lights. You can follow the wires from the transmission up to the main wiring harness up in the engine. And unless you have blown fuses, you are probably not looking for a short circuit. Rather it would be an open circuit (i.e. a broken wire or bad connection some place) that is preventing current from flowing. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs. r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

08-04-2008, 04:15 PM	#21 (permalink)
nomiss05 Registered User Join Date: May 2008 Location: cali Posts: 46	found the problem.. whoever owned the truck before me had a while plug thats just above the starter plugged into a green plug.. once i plugged the two while backs back tgether.. perfect.. now if only i knew what the green plug went to