98 s-10 lights flashing, help

I have a 98 S-10, automatic, 4-cyl, 2WD w/ electrical issues. About 2 months ago I noticed my blower fan would only work intermittently, then last month on 2 seperate occassions my headlights would quickly flash from low beam to daytime running lights. Now today when driving over 70 mph, it's no blower, lights flashing, speedometer neddle going up and down like crazy. I still have power and the engine runs fine. When I backed down to under 60 mph the problems stopped. Any ideas where I should look first?

I have a 98 S-10, automatic, 4-cyl, 2WD w/ electrical issues. About 2 months ago I noticed my blower fan would only work intermittently, then last month on 2 seperate occassions my headlights would quickly flash from low beam to daytime running lights. Now today when driving over 70 mph, it's no blower, lights flashing, speedometer neddle going up and down like crazy. I still have power and the engine runs fine. When I backed down to under 60 mph the problems stopped. Any ideas where I should look first?

Blower motor connections may be dirty, rusty, loose. Especially it's ground wire. Also, if you have one like me, that 4-5 wire plug ontop of airbox needs cleaning after awhile. I used a card board nail file, trimmed to fit, to clean out females of plug and males on box.

Don't use max speed more then few minutes, especially on older fan motors as I found out quick it burns out the brushes and motor dies.

Lights, well, I did have similar prob and found the green ground wire from left light to horn/body screw was loose and rusty. Cleaned and tightened and lights were fine.

Is speedo mechanical or electrical read out ? Again, maybe somethign loose.

Have you been hitting a lot of potholes ? :wink:

Any time you have simultaneous, multiple problems with seemingly unrelated circuits, you will find that a poor ground is the common denominator.

If the starter functions properly, the ground cable from the battery to the engine block, and it's connections, are ok. Check all connections on the body ground cables that are routed from the engine block to the body. On some vehicles, there is a smaller guage wire that is connected with the ground cable at the battery, if equipped, that wire is a body ground. All connections must be tight and free of rust and corrosion.

These are the fisrt things to check. It's also possible that there is a problem with the body computer, or even the ignition switch. If all ground connections are good, it will require more in depth diagnostics to locate the problem. Hope this helps.

Thanks guys. I was thinking the grounds would be a good place to start. Hopefully I can get to it this weekend and let you know what I find. BTW, speedo is mechanical, and potholes prevalent in NH.

Found the problem. After cleaning and securing all the connectors and ground cables, the problem continued to return. Had battery tested, it appears the plates were internally shorting. Replaced battery, problem gone.