Hi All, Just purchased my 08 H3 Alpha and love it! As is to be expected have had a few issues to take care of, and since my hobby is taking apart cars and rebuilding them (Restoring) most problems have been no problem thanks to some info from this forum.
But, I just noticed that my Backup lights are inop. Checked fuse and it was blown, replaced fuse, put in reverse and fuse blew...ok, short, removed tail lights, found trailer wiring tap on backup wire, disconnected it, tested for ground, no short in trailer wire. On to the next step.
I'm thinking Backup switch, searched forum, it seems no one has had this problem. Just want to know, before I crawl under or take to dealer, where is the switch. I read somewhere it's on the TOP of the transmission?? Could this be true. If so, can I reach it, or does the tranny have to come out?? OUCH! I'm getting that funny feeling of when my wallet gets thinner....I digress, any help would be much appreciated.

 

FWIW, assuming you have an automatic trans, my service manual indicates the Park/Neutral/Backup switch is on the left side of the transmission. The transmission control cable and an electrical connector attaches to this switch. I attempted to copy and paste the switch replacement diagram/procedure to this post but it didn't paste cleanly.

Does the transmission display indicator on the instrument panel indicate correctly for each gear selected? If so, IMO that would be a good indication the switch is not the problem.

 

Thanks, yes its an auto trans, V8 engine, I do have indicator lights all good. Hope you are right about on the side, will crawl under as soon as the sun comes up. Do visual inspect on wires, pull plug, shift to reverse, check fuse if it blows short before plug, if not, short in switch or beyond would be my troubleshoot. what do you think?

 

Now that I think about it, pulling the plug (thinking the short is before switch) wont work since the fuse only blows when I shift to reverse, it has to be the switch or beyond...DUH!

 

The fuse is before the switch in the electrical diagram, so if you pull the connector plug on the switch I don't believe that will tell you anything. The more informative test might be to pull the plug, and put a jumper between the pins that are closed by the switch. The service manual indicates the wires involved are the Pink (or Pink/Black) and the light green wires. If the fuse still blows, it's not the switch.

I'm trying to find the link where I downloaded the service manuals a few months back. They've been a real help on the few issues I've dealt with on mine.

 

Thanks again Cuc1949, I see you noticed my error...I have a service manual on order. I can't find any help online, if you find that link it sure would be helpful.

 

Looks like there might be a link to the manuals on this forum page:

https://www.hummerforums.com/forum/p...-26304/page11/

 

The link I found that shows the 2 separate switches (one on top of trans) is on page 46 of this pdf document.

http://schwarttzy.com/wp-content/upl...ing-2008-1.pdf

I hope that worked, first time attaching a link.

 

I believe the manual transmission has the switch on top of the trans, the auto uses the switch on the side of the trans for the backup circuit.

 

AHHH, Manual Transmission, different switch location, not 2 switches on diagram...Now that makes sense.