Strange Coolant temp issue

[Matt 4.3 TBI]

I've noticed since I installed my new speakers the temp gauge will read 10* higher when they're at a highway volume (ie loud enough to hear over wind noise at 70 mph). If I turn off the power to the stereo it will drop back down 10* within a few seconds. What the heck is going on with this? I got a little worried tonight since it was reading about 210-220* on the gauge after a 10 min highway trip at 60 mph. Coming back I kept the radio off and it was still 10* higher than normal, and it's only 45* out. I haven't hooked the laptop back up to see what the ECM is reading, but I'll take a trip tomorrow and get some data.

So, any ideas? I haven't found anything that was jarred loose after my unplanned trip off the road, anything I should take a look at? Also, what's going on with the speakers relation to the temp gauge? Is it just a voltage issue, am I gonna need to change the alt or put in an amp? Btw, the alt is a 100amp re-man unit from Advance Auto. Roughly 2.5 yrs old.

[bvr775]

sounds like a ground or your gauge may be going out of calibration. if you can get a cheap gauge to hook up under the hood it'll give you something to test against.

I have 3 backup(oil/temp/tach) gauges under the hood of my old 1st gen.They have saved me allot of headaches and my engine a couple of times. i have them so I can quickly mount them on the cowl because I have so many issues with the old wiring constantly breaking connection to the gauge cluster in the dash. It mostly just age(corosion,rust, losse connections), but I have some issues due to the prevous owners wireing skill. I'll fix it someday when to swamp between me and my shop drys up.

[T Man]

I would recomend some cheep aftermarket ones too. My buddy was having oil pressure problems, so we tore the engine apart, removed the front axle, oil pan, checked the oil pump, etc. Put it all back together, found out all it was was a bad gauge. 40 bucks later at autozone and he has good oil pressure

[Matt 4.3 TBI]

I've yet to see any aftermarket (much less CHEAP replacements for this dash:

http://www.h-a-s-t-e.com:81/albums/Interior/NewDash.jpg

:D

I'm not really convinced it's a gauge problem, it's never read wrong for me before, but I will go double check against what the ECM is seeing with its sensor tomorrow.

[rlith]

I would check the sending unit, not so much the gauge... As to replacements for the stock digital dash, this one is a direct bolt in...

http://www.dakotadigital.com/cartimages/STR6D-92C-PUlarge.jpg

[T Man]

go to autozone, they have a 3 pack of gauges, just hook those up under the hoood like you dont have a dash at all.

[extreme gmc]

since you installed your speakers? subs or small speakers? sound like you are having a voltage interference (emf) problem. GET IT UP TO OPERATING TEMP AND HAVE SOMEONE SIT IN THE CAB AND WATCH THE GAUGE WHILE YOU MOVE THE NEW WIRING THIS WAY OR THAT AND SEE IF IT DOES ANYTHING. IF NOT IT COULD BE A COWINCEADINCE (SPELLING)

[extreme gmc]

opps, didnt realize the caps lock was on...

[jjwalker]

Hell, since we got a temperature thread going...

When my truck is first started cold, as I drive it, it will get up 250* then shoot down to about 180, then go up and down slowly between 210 and 180.

The past 2 195* stats I have had did the back and forth between 180-210. The stock one in the original engine stayed at 210 all the time. My hypertech 160 stayed at 160 at all times. What the hell is the deal?

[bvr775]

my old s-10 has issues like that with the gauges. I had it tracked down to the gauges, but riped the dash out and put in a custom dash instead of fixing it.Thee brake peddle assembly had a brase on it that rubbed through and was makeing an itermitant short to ground. I should have replase the whole wiring harness, but shortcut the job. I'm dealing with awhole new set of problems now, but it's ok my engine still isn't finished.

[Maxx]

since you installed your speakers? subs or small speakers? sound like you are having a voltage interference (emf) problem. GET IT UP TO OPERATING TEMP AND HAVE SOMEONE SIT IN THE CAB AND WATCH THE GAUGE WHILE YOU MOVE THE NEW WIRING THIS WAY OR THAT AND SEE IF IT DOES ANYTHING. IF NOT IT COULD BE A COWINCEADINCE (SPELLING)


Yeah this is what i think it is except it could be from the speaker magnet. A magnet will induce a voltage in a wire as they passes back and forth across each other. Bouncing lose wire around new unprotect (unsheilded) magnet.

Solutions if this be the problem:
put a shield around the magnet
or use shielded wire that the magnet is inducing the voltage in.

[Matt 4.3 TBI]

There's very little room around the magnet, it rubs against the rear of the digital dash module slightly. What's good to use to shield the harness? I think you're right on with the magnet being the problem, since I faded it to the rear for the past few days and haven't seen the temp gauge fluctuating.

[bvr775]

copper mesh or tin foil will work. You can build a small cardboard enclosuer and glue the sheilding to outside of the enclosure.


i've also heard ductape makes a good sheild.I don't know how true it is, but i know for sure it makes great enclosures.

[Maxx]

make sure you ground the shield.

[Matt 4.3 TBI]

I'm going to get a new sensor today and swap this one out. I ran it on the highway a few nights ago with my laptop and WinALDL. The ECM was seeing a steady 176*, then when I turned on the stereo and the gauge read 210*, it saw 177*. It stayed there even after I turned off the stereo and the gauge dropped 10*.

Last night when I parked and shut it off, the gauge went up to 260* and stayed pegged. I opened the radiator cap (with gloves of course) and it was certainly NOT 260, or it'd be boiling! I unplugged the gauge's CTS, checked the wiring and plugged it back in. Then it read 200*. I think the headers may have cooked the sensor?

[rlith]

Definatly sounds like the gauge sensor.