Temp gauge issues after high output alternator install

[crotchss]

Hey guys, hope someone can give me some help. After installing a high amp alternator on my SS it seems my temp gauge is reading funny. At idle it's fine and reads 180* and I can let it sit and run for 20 minutes and it stays the same. Once I pull out on the highway even after 200 ft because the RPMs are up and the alternator is spinning faster the temp jumps to 220* and stays there and makes me nervous. I know the temp can't be that high with a 4" thick Griffin rad, Victor Jr water pump and dual 12" fans. I can get out and grab both top and bottom hoses and both are warm, but can easily be held, I get out my temp gun and they read 140* and 170* respectively. So what gives could the 275 amp alternator be messing with the gauge. I've changed out the sender with no luck. The alternator has alot of amps to run the cooling fans, vacuum pump for the brakes, 1600 watt stereo, etc. Anybody know what could be causing my issues? I know I'm asking the right group of guys, I'm sure someone has the answer. Thanks.

 

[pontiacgp]

are you running stock gauges?. I would check the ohm reading you have at the sender when your idling at operating temp and then rev the engine to see if the ohms drop which would send a higher temp to the gauge. If it doesn't drop them the problem is in the wiring and i would go back to checking the wiring to the alternator.

 

[crotchss]

Yes I have the stock gauges still. As far as the wiring to the alternator being bad or wrong, I think that is ruled out, since the only wire there is is the 8 gauge wire I upgraded to that runs to the battery and that's it. I just wandered if anyone knew if the extra amp output could screw with the magnetics in the gauge. The weird thing is none of the other gauges seem that affected, the tach twitches every now and then, and the oil gauge has always read a little off then on then off(which is why I run a mechanical oil gauge also). Hell maybe the printed circuit is bad(IDK), I have a new one I could install to check. It all just doesn't make sense to me and it's drving me nuts trying to figure it out.

 

[565bbchevy]

I'm curious who makes your 275 amp alternator and was it their recommendation to use an 8 awg wire to supply your alternator, it seems very small for the amperage capabilities of your alternator.
By comparison I was running a 200 amp Powermaster 1 wire alternator and used a 2 awg to supply it but it did not put out enough amps at idle
so I ordered a DC Power 180 amp and they told me my 2 awg would work but 1/0 would work best so that's what I put in

 

[crotchss]

565bbchevy, you were right, I just double checked and I have a 2 awg wire on my SS now. 8 awg is what I had on before with my Stinger 150 amp alternator. My 275 is from DC Power also and yeah the cable is a little small. But I still can't figure out the gauge issue.

 

[wrenchbend1]

I would like to touch on a few of Items that might shake something loose:
Engine cylinder heads factory or aluminum ?
the annoying grounds at the back of the cylinder heads ...connected ?
temperature sending unit is it wrapped in teflon tape ? is it screwed into an adapter thats wrapped in teflon tape ? are they both wrapped in teflon tape ?
Did the dashboard get any modifications due to a kickass stereo in the same timeframe as the gauge problem ?
Are there any electrical grounds disturbed under dash ?
Does the gauge wiring share the alternators conduit ?
Let us know mabe your answers give us more to go on !
Thanks !
Dave

P.S. Winter is mother natures way of saying "polish" 😀

565bbchevy, you were right, I just double checked and I have a 2 awg wire on my SS now. 8 awg is what I had on before with my Stinger 150 amp alternator. My 275 is from DC Power also and yeah the cable is a little small. But I still can't figure out the gauge issue.

 

[crotchss]

I have AFR aluminum heads on the engine, ground straps are on, temp sender is directly in cylinder head with no teflon tape. No modifications were made to the dashboard or grounds, just unhooked Stinger 150 amp alternator and replaced with the DC Power 275 amp, that's it. Still trying to figure it out. I have been wandering still if the alternator is supplying too much amperage and is messing up the magnetics of the gauge. My volt gauge reads normal at about 14 or 14+, but that is volts not amps. IDK what to look at next.

 

[pontiacgp]

Have you tried warning it up and then taking the alternator belt off to see how the temp gauge reacts when you fire it up without the alternator?

 

[wrenchbend1]

Pontiacgp makes a great point here , By removing the belt the alternator belt everything is battery with no alternator assist.
We are assuming that you dont have one of those fancy serpentine aftermarket set-ups , So Im going to try a couple of things more here that will require your assist. I belive your concern is that the high output alternator is not supplying so much current that it is causing "windings in the gauges" to create an electromagnetic interference in your readings.(especially the temp gauge)
I am sure you understand that these are analog gauges and they are aged and are in no way shape or form designed to be able to be "Precise" even when they were new ! But the difference here is the new high out put alternator.
It takes on average an engine with a good thermostat 15 minutes to reach temperatures close to thermostat opening.
So if you did your test with a cold engine you shouldnt be able to see 220 until after 10-15 minutes of running........Agreed ?
She should read cold till she heats up.If it reads hot while you know the engine is cold we are looking at a possible electrical anomaly.
The other area that might help is to put a DIGITAL voltmeter across the battery and rev the engine to see what output is doing at higher rpms. wouldnt hurt to put the positive lead of the DIGITAL voltmeter on the alternator battery lead also to see if there are differences.
Time for a stupid question : No possibility of a reverse rotation water pump here is there ??
Let us know ! its getting closer to that printed circuit board , but lets see what you come up with !!
Were watching ! your move !
Regards
Dave

I have AFR aluminum heads on the engine, ground straps are on, temp sender is directly in cylinder head with no teflon tape. No modifications were made to the dashboard or grounds, just unhooked Stinger 150 amp alternator and replaced with the DC Power 275 amp, that's it. Still trying to figure it out. I have been wandering still if the alternator is supplying too much amperage and is messing up the magnetics of the gauge. My volt gauge reads normal at about 14 or 14+, but that is volts not amps. IDK what to look at next.

 

[crotchss]

Thanks guys for the ideas. Well as far as taking of the alternator belt, can't as it runs the Victor Jr. water pump that has been on for years and is regular rotation. But I can just unhook the 2 gauge wire that runs from the alternator to the battery. The more things you guys come up with for me to check the more it is starting to point me towards maybe the printed circuit. I think at about the same time this all started was close to the time that I had removed the cluster to replace bulbs and paint the shadow box. At this time I also cleaned the printed circuit and reinserted it because my new one hadn't arrived yet and that weekend was our annual Cruise Nite, but if I remember correctly it was giving me some fits before that. Now that I have the new printed circuit maybe I should just tear it apart and slap in the new one. Yeah, I know these gauges were not the most accurate even when new, I have been contemplating even making a custom aftermarket set-up to fix any issues, it's just not in the budget right now. Again thanks guys for all the help, I'll post my findings after checking your suggestions.