2 problems with a 97 GMC Ext Cab

[rusty79beast]

I have a 97 GMC Ext Cab 2wd with the 5.7L Vortec and auto tranny. My first problem is the rear passenger side blinker and brake light! They don't work but the tailight works so my first thought was to replace the bulb but that didn't solve my problem. The blinker indicator in the truck blinks real fast when the right blinker is turned on, so I thought that might be a clue. The front passenger side blinker works fine but blinks real fast. The drivers side blinkers and brake light work fine. Maybe if I add a little blinker fluid it would fix the problem?? LOL OK for real, is this a simple ground problem or what??? My next problem is it seems like the engine is all of a sudden lacking power! It happened about 2 weeks ago, and now the engine makes a lot more noise but doesn't get going good. It almost sounds like the fan is extremely loud compared to usual. There are no check engine lights on, so I don't know what the problem may be. Seems like I lost almost half the acceleration power, but once up to speed you can't really notice anything wrong. Any help would be greatly appreciated Thanks guys

 

[diesel4me]

2 things....

The tailight assembly's on 88-up GM's have printed curcuit boards on the back side of them,that often corrode away,and break the current supply to the bulb..have to pull the tailight assembly off to see them..they fail quite often...of course it could be a bad wire somewhere too,or if you have a trailer hitch,the plug to the trailer is often to blame when someone just hacks into the harness to hook them up..the wires corrode or break..

As for you power loss,it sounds like from what your describing your fan clutch has seized up and now the fan is "direct drive"...you can feel the loss of power when this occurs quite noticeably..you probably need a new fan clutch..at least it wont overheat if its "locked" !..

 

[rusty79beast]

Can you test if it is a bad circuit board?? If so how would you test it? Same thing for the possible fan clutch problem, can you spin it by hand to test it or something?? That does sound like the problem I'm having. Thanks for your info!!

 

[diesel4me]

look at it!

The best way to check the tailight is to remove it--only by looking at the printed curcuit can you tell if its corroded and not letting current get to the bulb--(you could test for power at both of the contacts under the bulb with a test light,but you wont know if its a bad wire or a failed curcuit board without pulling it off and inspecting it..)

As for the fan clutch,I'd just get another one--if it has 100,000 miles its probably due for replacement--I dont know of any reliable "test" procedure for them..a used one from the junkyard will cost less than new,if you are fearful of wasting money on one in case its not the problem..but i'd say yours has locked up by the sound of your description...

 

[sweetk30]

you can get the boards at napa or carquest stores now, not just the dealers. and my 96 was starting to stumble at take off only when dead cold. found oil build up on the mass air flow. cleaned it off with brake clean and no more problems and fells more pepy.

 

[rusty79beast]

Can I just take the circuit board from the working side and swap it to the none working side to see if that's the problem?? Update on the engine lacking power: I drove about 500 miles this past weekend and now the truck has it's power back Maybe it was bad gas and the computer retarded the timing or something, or the fan clutch came unseized?? Anyway any info on the circuit board would be greatly appreciated Thanks

 

[sweetk30]

yes you can flip flop them to test.