No gauges, no reverse lights

[WahooSteeler]

So the PO on my truck had several questionable electrical connections. He had fog lights and an external stereo amp to my knowledge, and a hard-wired electric fan, which remains. (it comes on as soon as you turn the key to the "on" position). Fog lights are gone, he kept the amp and I replaced the stereo with just a new head unit. My truck has the heavy duty cooling option so I assume this electric fan is factory and was supposed to be thermostat controlled. I don't mind the "always on" electric fan, just giving as much detail for any feedback. I want to remove all of these excess connections as I believe they may be causing other problems. Truck is an 88 4.0/AW4. 

 

Other info.....gauges work with, I think, a 15 or 20 amp fuse. Don't want to do that. It pops 7.5's and 10's. So not sure what to look for on that, I assume if it was a short it would pop any size fuse, not just the small ones. That's what's making me think the panel is overloaded somehow with the PO's wiring crap and asking for some direction.  

 

I am also working on the no reverse light situation. It was losing all interior lights and no tail lights when I pulled the headlight switch. Rear brake lights and turn signals worked. When I pulled the tail lights recently to start looking for the problem,  I noticed the pass side reverse socket had a rusted out connection on the hot lead inside the socket. Once I disconnected that and put in a new fuse (proper size too), I now have all interior lights and tail lights. Still have brake and turn signals, but after replacing the socket still no love on the reverse lights.Traced the wire loom best I could and did not see anything obvious. Need to check the connector behind the driver rear tire as Pete often suggests. Has a trailer harness, will check over those connections again also. Hoping I don't have to mess with the NSS. Have not tested for power at the sockets yet. I searched and read lots of "no reverse light" threads last night, so I think I have good direction there.

 

Thanks in advance............. 

[87MJTIM]

The reverse light may be the back up switch on the trans.  Test the switch by turning the ignition on, not running, put the gear lever in reverse.  Using test light or multi meter, see if there is power going to the rev. lights.

 

Do you have the 88 electrical wiring manual?  

 

[WahooSteeler]

I see references to the "back up switch" and the "NSS" in a lot of the searches I looked at. I'm aware of the NSS, is the "back up switch" the same or another part, for my clarification. 

[mjeff87]

Holy *%#$& Greg.....you got a real butcher shop going on there in your fuseblock

 

The dash light circuit is tied into the rear lighting circuit, all controlled by the 5 amp "INST PNL" fuse in the block...check that first.  The genius engineer theory back in the day was that if your rear lights went out you wouldn't know, so they tied the circuit to the dash panel.  If your dash lights died, you would then know your rear end was dark.  Heh.

 

Not sure if the backup lights are on the same circuit, but that would be a start.

[WahooSteeler]

8 minutes ago, mjeff87 said:

Holy *%#$& Greg.....you got a real butcher shop going on there in your fuseblock

 

The dash light circuit is tied into the rear lighting circuit, all controlled by the 5 amp "INST PNL" fuse in the block...check that first.  The genius engineer theory back in the day was that if your rear lights went out you wouldn't know, so they tied the circuit to the dash panel.  If your dash lights died, you would then know your rear end was dark.  Heh.

 

Not sure if the backup lights are on the same circuit, but that would be a start.

Yeah, notice the 2 fuses he had jumpered in. For some reason I think one of those is wired for the radio. Since I am not running any kind of accessories I am going to pull both of those and hope that nothing stops working LOL. 

[Ωhm]

Many names for reverse lamps/backup lamps/rear lamps/rear backup lamps. Many names for Gear Selector Switch/Neutral Safety Switch (NSS)/Backup Lamps Switch. Auto or Manual makes a difference for the switches.

[87MJTIM]

The back up switch is a separate part on the trans.  It has a two wire connector. The switch closes the circuit to feed pwr to the reverse lights.  If the switch is bad, then no rev lights.

[mjeff87]

I *think* I still have a spare NSS in my parts pile in the shed, from an 88-89 XJ (I just saw it hanging off an AW4 in the junkyard one day and grabbed it...all my junk was manual but I couldn't just leave it there, lol).  If you need it, I can see if I still have it (likely) and send it to ya

[SVPete]

Check the 7.5 amp fuse marked TRANS. The reverse lights run through that fuse.

[WahooSteeler]

Problems solved. Reverse lights are working, gauges working. 

 

Scratching my head on the reverse lights though. Last night while working on them it seemed clear they were not getting power. Trans fuse was good, all other fuses were good except for gauges fuse. At the end of messing with it last night, having been popping 7.5's and a 10 on the gauge fuse slot, I brought them inside to look closer if the all popped because some of the ones I used had really dark red plastic and it was hard to tell if they popped unless I shined an intense flashlight on them. I guess I pulled the trans fuse too but that one was good. So tonight I start probing with a test light and I'm not getting anything. Then I remember, duh, I pulled the fuse last night and took it inside to double check it. I also realized at that point that last night I never heard the electric fan running and I planned on upping the amps to see which fuse would "hold". I put in a 15, my fan came on and the fuse held. So now I know the PO wired the electric fan through the gauges fuse, which explains why 7.5A or 10A wasn't enough juice. Now that I know it's the electric fan that is requiring that slot to have a 15A in it, I'm reasonably comfortable it's not going to melt the block. So then I also put the 7.5 back in the trans slot and......reverse lights! Not sure how they suddenly worked, but for now I'll let it be and just be happy they do. I DID rake the gear selector through all gears and jiggled it between park and reverse a few times, but I'm not convinced that did anything.  

 

I'm still going to begin the process of cleaning up the rats nest of unnecessary taps, but after I get it to pass inspection next week! My son was pretty stoked tonight that it's ready to get inspected and should pass. He'll be eligible for his license next Thursday. 

 

 

 

[WahooSteeler]

So now my reverse lights will come on, but only if I pull the shifter back enough and hold it to where I can feel it getting ready to go in to neutral. They do not come on with the shifter just sitting naturally in the reverse position. Would this be more likely to be the NSS or the backup switch as the culprit? 

[HOrnbrod]

Shift cable out of adjustment at the tranny. Try adjusting it to get some of the slack out.

 

http://www.lunghd.com/Tech_Articles/Transmission_and_Transfer_Case/Transmission_Automatic_Shifter_Adjustments.htm

 

https://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c152800a9e62

[WahooSteeler]

That makes a lot of sense Don, shifter definitely has plenty of slack between gear selections.