Tac light goes out when lights turned on

Swansen · 07-15-2008, 08:01 PM

88 PU, its an aftermarket tac, but this just started happening after the fuse blew for the running lights and dash lights. So when the lights are off the tac works, but when i turn the lights on, it doesn't illuminate and stops working.

rowdy235 · 07-15-2008, 08:28 PM

something internally in the tach? Only thing that makes sense to me.

4Crawler · 07-15-2008, 09:47 PM

Check your wiring, most after market gauges are wired to have a positive wire for the light and the bulb is grounded to the case of the gauge (i.e. tied to the vehicle ground). The dash lights are wired with a floating ground which goes through the dimmer (rheostat) to let the dash light intensity be adjusted. If you tie a hard grounded device into the dash lights (with a floating ground), things like that can happen. Best bet it to tie the tach into a separate circuit (that switches on and off with the ignition) and if you want the back light to turn on and off with the lights, hook it to something like the parking lights, not to the dash lights. It won't dim, but you can add an in-line resistor if the light is too bright.

Swansen · 07-16-2008, 05:43 AM

parking lights??? i don't know if i have a circuit for that, as its a manual, unless i'm mistaken what you mean by parking lights. It said in the manual to have a good clean ground. So i just ran a separate ground straight to the battery. Everything else is wired in with the head unit. On that, it has an illumination, positive, negative, and signal leads.

ozziesironmanoffroad · 07-16-2008, 06:21 AM

ok to turn on your headlights you twist the lever so it clicks twice, right? turn it once. when your brakelights and marker lights are on. thats what hes meaning. wire it into those lights.

zlathim · 07-16-2008, 06:33 AM

Quote:

Originally Posted by ozziesironmanoffroad

ok to turn on your headlights you twist the lever so it clicks twice, right? turn it once. when your taillights and marker lights are on. thats what hes meaning. wire it into those lights.

Fixed it for you.

4Crawler · 07-16-2008, 07:06 AM

Quote:

Originally Posted by Swansen

parking lights??? i don't know if i have a circuit for that, as its a manual, unless i'm mistaken what you mean by parking lights. It said in the manual to have a good clean ground. So i just ran a separate ground straight to the battery. Everything else is wired in with the head unit. On that, it has an illumination, positive, negative, and signal leads.

Parking lights pr running lights is what I think you called them. The orange ones up front and the red ones in back that come on before the head lights.

What is the head unit "illumination" circuit hooked to?

Swansen · 07-18-2008, 04:59 PM

Yes, so i am thinking it might just be the tac. I haven't jumped very far into the wiring, but my head unit it wired into the illumination lead that comes from the trucks wiring harness for the radio. On that, i noticed while driving today that it was stuck at 2,000 RPMs, so thats why i am guessing its the tac??? but i just check and it went back to rest. I don't know, but its weird that the tac is reliant at all on the illumination lead, i shouldn't even have to have it hooked it, all it should need is a signal, power and ground. hmmm... i wonder if i'm not getting a clean 12v, i guess i'm going to have to invest in a volt meter.

4Crawler · 07-18-2008, 05:21 PM

Tach may have a backlight but should work without that hooked up (just hard to read it at night). Volt meters are inexpensive (under $5):
- http://www.harborfreight.com/cpi/cta...emnumber=92020

Swansen · 07-19-2008, 11:59 PM

Right, well, haven't gotten a volt meter yet, but i observed something weird. When the lights are turned off the tac is illuminated ????? thats confusing to me. So, what i am confused about right now is, why it worked fine before the fuse blew, but now the illumination is backwards??

Swansen · 07-22-2008, 06:29 PM

Turns out, it was a bad ground, the connection was loose, on a side note there should be a "solved" button for threads.

07-15-2008, 08:01 PM	#1 (permalink)
Swansen Registered User Join Date: Jan 2007 Location: Michigan Posts: 381	Tac light goes out when lights turned on 88 PU, its an aftermarket tac, but this just started happening after the fuse blew for the running lights and dash lights. So when the lights are off the tac works, but when i turn the lights on, it doesn't illuminate and stops working.

07-15-2008, 08:28 PM	#2 (permalink)
rowdy235 Registered User Join Date: Sep 2007 Location: Sweet Home, OR Posts: 1,375	something internally in the tach? Only thing that makes sense to me. __________________ Daily Driver: 1982 Toyota Pickup Base 2WD 22R, TRD Cam,5-sp Manual, Toyota Truck Nation High Miler- 300k+ MPG: 25/32 Off-roader: 1990 Honda H3011SA Riding Lawnmower, 11hp OHV engine, Carlisle SNOW-HOG Tires MPG: 1 Day of "Wheeling" per gallon Come to the 2nd Annual Oregon Yotatech Meetup! June 26-29, 2009: Browns Camp OHV Park http://www.yotatech.com/f5/oregon-yo.../#post50902592

07-15-2008, 09:47 PM	#3 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,259	Check your wiring, most after market gauges are wired to have a positive wire for the light and the bulb is grounded to the case of the gauge (i.e. tied to the vehicle ground). The dash lights are wired with a floating ground which goes through the dimmer (rheostat) to let the dash light intensity be adjusted. If you tie a hard grounded device into the dash lights (with a floating ground), things like that can happen. Best bet it to tie the tach into a separate circuit (that switches on and off with the ignition) and if you want the back light to turn on and off with the lights, hook it to something like the parking lights, not to the dash lights. It won't dim, but you can add an in-line resistor if the light is too bright. __________________ 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

07-16-2008, 06:21 AM	#5 (permalink)
ozziesironmanoffroad Contributing Member Join Date: Sep 2007 Location: Spring Valley, CA Posts: 4,167	ok to turn on your headlights you twist the lever so it clicks twice, right? turn it once. when your brakelights and marker lights are on. thats what hes meaning. wire it into those lights. __________________ The 22r series engines are made from the fires of hell, and will fight tooth and nail to not be sent back. 1988 Toyota P/U 4x4 22RE 258,000 miles on original motor pioneer CD deck 31x10.50x15 BFG A/T BAJA 100W lights on prerunner bumper KC Daylighters 100W rancho rs5000 MUD IS A VALID PAINT JOB! If not living life to the fullest, why live it? my trucks official buildup thread

07-18-2008, 05:21 PM	#9 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 6,259	Tach may have a backlight but should work without that hooked up (just hard to read it at night). Volt meters are inexpensive (under $5): - http://www.harborfreight.com/cpi/cta...emnumber=92020 __________________ 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

07-16-2008, 05:43 AM	#4 (permalink)
Swansen Registered User Join Date: Jan 2007 Location: Michigan Posts: 381	parking lights??? i don't know if i have a circuit for that, as its a manual, unless i'm mistaken what you mean by parking lights. It said in the manual to have a good clean ground. So i just ran a separate ground straight to the battery. Everything else is wired in with the head unit. On that, it has an illumination, positive, negative, and signal leads.

07-18-2008, 04:59 PM	#8 (permalink)
Swansen Registered User Join Date: Jan 2007 Location: Michigan Posts: 381	Yes, so i am thinking it might just be the tac. I haven't jumped very far into the wiring, but my head unit it wired into the illumination lead that comes from the trucks wiring harness for the radio. On that, i noticed while driving today that it was stuck at 2,000 RPMs, so thats why i am guessing its the tac??? but i just check and it went back to rest. I don't know, but its weird that the tac is reliant at all on the illumination lead, i shouldn't even have to have it hooked it, all it should need is a signal, power and ground. hmmm... i wonder if i'm not getting a clean 12v, i guess i'm going to have to invest in a volt meter.

07-19-2008, 11:59 PM	#10 (permalink)
Swansen Registered User Join Date: Jan 2007 Location: Michigan Posts: 381	Right, well, haven't gotten a volt meter yet, but i observed something weird. When the lights are turned off the tac is illuminated ????? thats confusing to me. So, what i am confused about right now is, why it worked fine before the fuse blew, but now the illumination is backwards??

07-22-2008, 06:29 PM	#11 (permalink)
Swansen Registered User Join Date: Jan 2007 Location: Michigan Posts: 381	Turns out, it was a bad ground, the connection was loose, on a side note there should be a "solved" button for threads. Last edited by Swansen : 07-22-2008 at 06:31 PM.

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