GV Tail Lights, How To Guide

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GV Tail Lights, How To Guide

December 11, 2015, 09:28:45 am

Topic: 1993 GV Tail Lights, how to refurbish, repair and improve.

I have never been happy with the Isuzu-sourced rear lights on our GV. They are (IMO) too small, too dim, and woefully ineffective. I have often considered the question of how to improve them, but so far it's been "all thought and no action". After our last trip, I discovered that one of the amber turn signal lenses had started to lift up at one end, and was in danger of falling off. This fact prompted me to get off my duff, and finally try to do something to rectify the situation. If you have ever looked into trying to replace one of these GV tail light assemblies, you will know they are VERY hard to find. To my knowledge, no new reproductions are available, so your only source is from the dwindling supply of new old stock (NOS), or from old coaches (or old Isuzu cars) being parted out - good luck with that.

First Step: Remove the light assembly.

If you have never had to replace a GV rear light bulb, you are in for a treat! Working on the rear lights is awkward and can be more or less challenging, depending on the layout of your engine compartment. On our coach, the driver-side light is unobstructed and fairly easy to reach...the curb-side light not so much, due to the coolant reservoir partially blocking my view. To get access the rear of the lights, you first must remove a fiberglass dust cover (photo 1). It will probably be attached with 2 of the typical (Foretravel favorite) square-drive screws, one at each end. There might be some caulking material or a foam gasket holding the cover in place, so you may have to tug a bit to pull the cover off.

Once the cover is out of the way, you are looking at the back side of the light unit (photo 2). The next step is removing the "bulb holder". This is a black plastic cover that incorporates the wiring harness connection on the bottom. It is secured by 3 plastic tabs on the bottom, and 3 hooks on the top. You depress the tabs to "unlock" the cover, then rotate it up and out to free the hooks and remove it (photo 3). It is not necessary to disconnect the wiring harness plug prior to removing the cover.

When the "bulb holder" is free (but still hanging on the wiring harness), you will be able to see a flexible printed circuit inside along with the light bulbs (photo 4). If you are simply replacing a bulb, this is as far as you need to go. Later in this thread, I will go into more detail about the bulbs and possible upgrades, so stay tuned. For now, I'll just note that there are 4 bulbs - 2 single filament and 2 dual filament. The single filament bulbs are used behind the amber turn signal lens, and the white (clear) backup lens. The dual filament bulbs are used behind the 2 red running light/stop light lenses. Note: the GV rear turn signal is a single-function light, as opposed to the front turn signal, which is a dual-function light.

If you want to completely extricate the light assembly, you must next remove 9 nuts and washers...5 along the top of the unit, and 4 along the bottom (photo 5). A deep 5/16" socket (1/4" drive) on a short extension is handy for this task. Try to be gentle when unscrewing these nuts - the associated studs are simply embedded in the plastic lens unit, and can pull out if you are too rough. I managed to dislodge one of them - I will reseat it with epoxy glue (photo 6). When you are sure all the nuts have been removed, attempt to pull the lens assembly outward away from the coach body. Mine were both stuck on pretty good by a combination of old rubber gasket and white caulking material, but they finally came loose with persistent, GENTLE persuasion. The metal backing plate through which the lens assembly was bolted will probably stay stuck in place - mine did on both sides (photo 7). If it does not, no big deal - just note how it is positioned for future reassembly (it can only go on one way).

For the next step, take the light units to your work bench (photo 8.)

Re: GV Tail Light, How To Guide

Reply #1 – December 11, 2015, 09:30:58 am

Second Step: Clean and Repair the light assembly.

As I mentioned earlier, one of my light units was starting to come apart. After I removed the unit from the coach, I could see the problem. Each light is made up of 3 discrete sections, which are bonded together to form a single unit. There is the red lens (with clear backup light insert) which is one piece; the amber turn signal lens which is a separate piece, and the rear reflector/backing section. On one of my lights, the amber lens had broken loose at the inboard seam, and had lifted up about 1/2 inch. (sorry - neglected to get a photo of pre-repair condition) If the other end had also come loose, the lens could have easily fallen off going down the road. (I believe I once read on the Forum about this exact thing happening to another member) In addition, (unlike other older automobile tail lights I've worked on) since the whole thing is bonded into one piece, there is no way to refinish the inside of the rear reflector portion (with silver paint) and improve the light reflectivity. Dumb Design!

The fiberglass "dust covers" on my coach had been only marginally effective, so the back sides of my light units were covered with a thick coating of dirt. Not wanting to risk damage to the fragile printed circuit, I left the bulb holders in place connected to the wiring harness, and just cleaned the loose dirt off them with a stiff paint brush. I gently blew out the bulb holder sockets with my compressor air gun. I was surprised to find the sockets in good condition, with zero rust, so apparently there has been minimal moisture intrusion over the years (photos 9 & 10).

I took the light assemblies in the house, and soaked them in a tub of warm soapy water. I used a soft bottle brush to gently clean out the inner cavities. (Note to self: When you wash filthy car parts in the bathroom, be sure to clean up the dirty bathtub BEFORE the DW sees it) Got the lights all dried off with a towel and air gun, then took them to my bench. I decided there was enough "meat" on the failing amber lens to drill a few small holes through it and the rear reflector. I inserted two 1/8" stainless bolts in the broken end, and another bolt in a third hole on the other (still firmly attached) end of the lens (photo 11). After warming the plastic with a heat gun, I GENTLY pulled the raised end of the lens back into place with the 2 bolts, until it was about 95% restored to proper position. There is still a slightly raised lip (photo 12), but I decided to not push my luck and risk cracking the lens. I think it looks fine, and now I am sure it will not fall off. I then applied the same bolting technique to the amber lens on the other unit, to preclude future problems (photo 13).

With the light assemblies now clean and repaired, my final step was to employ a polishing compound to restore the outer surface of each lens. I used a product called Meguiars #67 One Step Compound (photo 14). I have found this stuff works GREAT on many parts of the coach, including the exterior gel coat, aluminum mirrors and wheels, and plastic lenses! It removes scratches, oxidation, discoloration and dirt from almost any surface (test in a inconspicuous spot before using). A little hand work with rag and polish made 98% of the surface blemishes and haze disappear, and resulted in the lights looking almost like new! (photos 15 & 16). I believe I have now gotten them into as good a condition as possible, so the next logical step will be to upgrade the light source.

Re: GV Tail Light, How To Guide

Reply #2 – December 11, 2015, 09:32:25 am

Third Step: Improve the Light Output.

At this point, most members would probably suggest trying LED bulbs. However, I want to first investigate how much improvement can be made while sticking to incandescent bulbs. Why? First of all, I am (somewhat) Old School, and not yet ready to completely abandon the incandescent bulb. Don't get me wrong - I LOVE LED flashlights! And I just recently used LED units to replace the fog lights on our coach, with excellent results. Even so, I still think old-style Edison bulbs can function very well in many applications. In addition, I have read numerous online reviews of using LED conversion bulbs in auto tail lights, and apparently many customers are disappointed in the results. Some say the (imported) bulbs, although expensive, are poorly constructed and have a very short lifespan. Others say the light emitted by the LEDs is either too dim, or else is concentrated in one bright red central spot on the lens, leaving the rest of the lens dark. So, I will first try to optimize my rear lights using the best currently available incandescent bulbs. Then, if I am still unsatisfied with the light output, I will try experimenting with LED conversion bulbs.

Some of the following information is taken from a post I found online at another forum. In case you want to read the whole post, here is the link:

2357 tail lite bulbs or 1157? [Archive] - For A Bodies Only Mopar Forum

As I mentioned earlier, each rear light assembly uses 4 bulbs - 2 single filament, and 2 dual filament. As you can see in the close-up photo of the back of the bulb holder, the original Koito factory fitted bulbs were 1073 (single filament) and 1034 (dual filament) (photo 17 & 18). That ancient bulb spec was superseded in the early '70s by the 1156 (single filament) and 1157 (dual filament). When I opened up my lights, I found each unit had two of the original Koito brand 1073/1034 bulbs, and two newer 1156/1157 replacement bulbs. All the bulbs, although dirty and somewhat "darkened", appeared to be in good condition, but were barely bright enough to be seen in broad daylight, and not a lot better at night. Hence, my quest for improved performance.

Today, the best (conventional) bulb you can use in place of 1157 is a 3496. Apparently, the only place you can purchase the good ones is from a Honda (auto) dealer. Part number is 34906-SL0-A01. This bulb draws the same amount of current as 1157, but is brighter and more efficient. It also has a nickel-plated base that is more corrosion resistant than the plain brass on the 1157. Beware of cheap rip-off imported 3496 copies. Only one company makes quality 3496 bulbs and that is Stanley, and they are only available through Honda dealers. I ordered mine online from:

OEM Honda Part 34906-SL0-A01 | Bulb (12V43/3CP) (Stanley)

The best replacement for 1156 in all applications except backup lights is a 3497 - also available exclusively from Honda dealers. Part number 34903-SF1-A01. Same benefits and comments apply as described for the 3496 (above). I ordered them from the same online dealer. (see link above).

The best "upgrade" bulb for use in backup lights is a P796 (no particular manufacturer is mentioned). It is a 35W halogen bulb that produces twice the candlepower of a 1156, at only slightly higher wattage. The extra power draw is minor (no problem for stock wiring), and the filament is properly positioned so the reflector works correctly. Should make the backup lights much more effective. I found these bulbs available on eBay from several vendors - here is one:

#796 HALOGEN MINIATURE BULB BA15S BASE, T4 SC BAY 12.8V 2.7A 60CP, 796,...

Armed with this information, I ordered the above mentioned bulbs. While waiting for them to arrive, I reinstalled the now cleaned-up tail lights in the coach. If nothing else, they sure LOOK a lot better! (photo 19 & 20) After the new bulbs arrived (photo 21), I decided to try a "side-by-side" comparison test. I dusted off the (newest) old bulbs (1156/1157) and inserted them in the right tail light. I installed the new higher-performance bulb set in the left tail light. Then I tried them out, both in bright sun light, and after dark. Results of test revealed in next post.

Re: GV Tail Light, How To Guide

Reply #3 – December 11, 2015, 09:33:22 am

Forth Step: Test.

With the old standard bulbs in the passenger side light, and the new bulbs in the driver side light, I tried out the lights in broad daylight. The results were........somewhat disappointing, simply because BOTH lights were now much improved in brightness. I had expected a big difference in perceived brightness, but what I observed was almost equal performance. I think part of the reason for this was the fact that I had cleaned 20+ year's worth of dirt out of the light assemblies. This allowed even the old bulbs to appear much brighter (in daylight) than they had before, and reduced the visual impact of the high performance bulbs.

Next, I waited until after dark, then tried the lights again. This time, the relative difference in performance was much more evident. The more expensive bulbs are noticeably brighter in all positions. The turn signals are greatly improved, as are the brake lights. The new back-up light bulb actually throws some useable light behind the coach. Once again, however, the light output from the old bulbs looked very good, and would be perfectly acceptable in most cases.

The next day I finished replacing the bulbs in the passenger side tail light, and also installed fresh 1157 bulbs in the front turn signal units. I also went around the coach and removed the lens from each of the 14 rooftop clearance lights. I cleaned the accumulation of dirt out of the lenses, and replaced several burned out bulbs. That evening, I tested the complete light package once again, and was totally satisfied with the tremendous improvement. Much brighter and SAFER!

Bottom line: The greatest percentage of improvement was the result of simply cleaning all the dirt out of the light units. This is good news, because all this costs you is a little time and effort. After the rear light units are clean (inside and out), if you want to spend the extra money on the high performance bulbs, they will provide a additional benefit. If not, you could simply use fresh* standard 1156/1157 bulbs, and still get pretty decent lighting performance. Your choice!

*Note: Old bulbs get "dark" inside as they age. Replacing your incandescent bulbs on a regular basis will yield best possible performance.

I do plan to test some LED bulbs, to see if they will work any better. In the Isuzu tail light units, the bulbs are held at a 45 degree angle to the vertical lens face. I think this is not the ideal setup for using LEDs, which generally work best in either a vertical or horizontal position (relative to the lens). If I have any luck with the LEDs, I will report back at a later date. Thank you for your attention, and let the comments commence!

Re: GV Tail Light, How To Guide

Reply #4 – December 11, 2015, 09:49:37 am

Chuck,

EXCELLENT write-up.

I found dust on the bulbs to be the most significant cause of dim tail lights. Pulling the "bulb assembly" every other year and just wiping them off proved to restore brightness. Did not see any sign of corrosion/moisture intrusion.

Re: GV Tail Light, How To Guide

Reply #5 – December 11, 2015, 09:50:18 am

Great write up Chuck!!! I too have been wanting to do an upgrade with the rear lights, Since she is in hibernation right now it looks like this will be my first spring project. Thank you!

Re: GV Tail Light, How To Guide

Reply #6 – December 11, 2015, 10:02:54 am

I agree, Brett. The Isuzu light unit was obviously designed to be installed in a less dusty environment, like the trunk of a car. There are numerous (ventilation?) holes in the assembly that allow dust and dirt to easily enter.

Re: GV Tail Light, How To Guide

Reply #7 – December 11, 2015, 10:12:44 am

Chuck, do the 3496 & 3497 bulbs get hotter than the 1156 & 1157 bulbs? If they do, couldn't they cause issues with the lens and the printed circuits?

Re: GV Tail Light, How To Guide

Reply #8 – December 11, 2015, 10:28:35 am

Nitehawk,

My understanding (based on the linked thread from the other forum) is that the 3496/3497 bulbs do not draw more current, but are simply more efficient. Therefore, I assume (always dangerous) that they will not burn "hotter".

The halogen 796 bulb does draw more current, and will be a "hotter" burning bulb. Whether or not this causes the lens to over-heat is yet to be seen. Since the reverse lights are seldom used for more than a few minutes at a time, I do not anticipate any problem.

Re: GV Tail Light, How To Guide

Reply #9 – December 11, 2015, 10:34:37 am

Great job on the write up Chuck. This kind of step by step helps a lot of folks get up the courage to do these tasks themselves.

LED bulbs will be cooler. They're getting much cheaper too. Most are rated in Lumens. 12.57 x candlepower = lumens. With the bulbs at an odd angle the projector type LEDs may not work as well. Before I had my tail lights redone at Xtreme I had replaced all of the bulbs with LED. Much brighter.

Re: GV Tail Light, How To Guide

Reply #10 – December 11, 2015, 10:43:29 am

Just had a thought (strained something again).(top of my head suddenly got real warm!)
I wonder if one had a complete Isuzu taillight assembly if the black plastic backing board that holds the sockets and circuit could be modified to hold LED bulbs in the necessary orientation required for maximum lighting. Also eliminating the printed circuit and hard wiring instead.
The LED lighting portion is usually smaller than the 1156/1157 glass bulb so it might be possible to change the orientation.
Reason I "wondered" about this is I seem to see more & more circuit failures and the Isuzu sources for the lights are disappearing due to ageing out.

Re: GV Tail Light, How To Guide

Reply #11 – December 11, 2015, 10:45:06 am

Chuck,
An excellent and thorough write up. Good job.
May your star shine brightly!!
Brian.

Re: GV Tail Light, How To Guide

Reply #12 – December 11, 2015, 10:51:42 am

Nitehawk,

Anything is possible....but.....to reposition the bulbs you would have to drill (additional) holes through the (reflector) back portion of the light unit. I fear this would distroy the existing reflective area behind the lens. The LEDs might put out enough additional light that this would not matter - I don't know. You would totally mangle the original design in the modification process, so if it didn't work out, you would be.....

Re: GV Tail Light, How To Guide

Reply #13 – December 11, 2015, 11:09:46 am

I guess I will have to go up in my garage attic and take out my two light assemblies (no lens assemblies tho) and select the bad one. Then see what "might" be possible.

Re: GV Tail Lights, How To Guide

Reply #14 – December 11, 2015, 12:01:08 pm

Chuck

Great write up. You've set the bar pretty high for taillight renovation documentation. Lots of valuable information that will be used in other parts of our coach.

Good job..... Yet another part of your GV that LOOKS LIKE NEW

Re: GV Tail Lights, How To Guide

Reply #15 – December 11, 2015, 12:05:25 pm

Well, I found the circuit boards and I took pictures of the driver's side circuit that a friend of mine "repaired while we were at a campground.
The first one is showing where he soldered a wire in the socket on a contact point and how he routed the wire and anchored it with (what else?) Shoe Goo!!
The second picture you can see the broken circuit to the right of the bulb on the edge of the plastic. It appears as a brown/copper colored section.
He also determined where the wire had to be soldered on the back of the main connector.
The last picture shows how he was able to bend the tabs if necessary. I don't remember if he did, tho.
I do know the repair is still good. I purchased replacements just in case, put them in, and kept the old ones as backups--just in case.
Now I have to think thru and consider the possibility of replacing the incandescent bulbs with LEDs.
Might be a market for the conversions?

Re: GV Tail Lights, How To Guide

Reply #16 – December 11, 2015, 12:50:55 pm

OOPs, I have to correct my previous post.
The break in the light circuit is on the backside of the main connection block, not the bare wire to the right of the light. That is just another reason I bought replacements. Abrasion and corrosion had taken their toll on the entire printed circuit.

Re: GV Tail Lights, How To Guide

Reply #17 – December 12, 2015, 03:36:53 pm

I used these for 3157 replacement with my 99 Ranger (and they are a huge improvement), but they are available in 1157 format too. This link takes you to the 1157: Amazon.com: JDM ASTAR 1200 Lumens Extremely Bright 144-EX Chipsets 1157 2057...
Remember that most LEDs associated with a blinker will need a load resister added in line to operate correctly - and they get HOT.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: GV Tail Lights, How To Guide

Reply #18 – December 12, 2015, 04:35:50 pm

Dave,

Fresh 1157 bulbs in my front turn signal/running lights make them pretty darn bright! I don't think I would require many more "lumens" in that position. I tried using one of the Stanley 3496 bulbs up front, but there was not enough difference to matter, so I went back to a "fresh" 1157.

I might pick up a set of those LED bulbs and see how they work in the tail lights. Thanks for the tip.

I have also installed some brighter Hella bulbs in the headlights, but I hesitate to recommend these on the Forum, since they are technically not "street legal". They DO brighten up the headlights considerably! If you are interested in experimenting with brighter bulbs (Off Road use only), here is the link:

Amazon.com: HELLA HLA-H83155131 HB1 9004 12V 100/80W Off Road Use: Automotive

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: GV Tail Lights, How To Guide

Reply #19 – December 12, 2015, 04:42:32 pm

Quote from: Chuck & Jeannie – December 12, 2015, 04:35:50 pm

Mike, yours may be different, but my amber front turn signal/running lights use the 1157 bulb, not the 3157.

My RV buddy told me the same thing; some use the 1157 and others use the 3157; something about the bayonet fitting, go figure.

Re: GV Tail Lights, How To Guide

Reply #20 – December 12, 2015, 04:51:01 pm

Quote from: mike leary – December 12, 2015, 04:42:32 pm

My RV buddy told me the same thing; some use the 1157 and others use the 3157; something about the bayonet fitting, go figure.

I've taken out that turn signal module, not a lot of fun. Now I'm wondering whether I've got a 3157 or a 1157!

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