Im amazed that some guys don,t look at the clues


Staff member
I was over a friends house to help him test and isolate a problem on his 1995 lt1 corvette, it seems it recently started running like crap, for seemingly no reason.
well AFTER HEARING IT RUN I SUGGESTED WE DO A TUNE UP, AND PULL TROUBLE CODES , I also strongly suggested we get out a multi meter and do a few tests,
this infos bound to be helpful at times
Sensor Locations


Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

Sensor Outputs:

Measured Value

Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

but like many guys would have, he decided to drive the corvette to the local NAPA store with me as a passenger, before we did any testing.

and anyone who says they have not done something that came back to bite them later in a similar manor is obviously lying as we all do this.
as were driving I'm watching the dash voltage gauge and notice the volts while were driving are slowly dropping and the engine rpms have zero effect , that's a very good clue that the alternators not working or the battery is defective or the engine grounds are loose etc. and sure enough while hes in the store he left the engine idle as he stated it has a tendency to quit or stall,, or be hard to re-start, the battery voltage dropped to 9 volts and the engine stalled and would not restart.
I'm betting its time for a new alternator. (further testing to follow) he got the car towed home !

get out a multi meter and test, its really easy, measure the voltage at the battery terminals before you try to start the engine, it should be 12 + volts but might be a bit less, if the batterys been run down , cranking the engine over, hit the key, if the engine starts when it spins over with or without a jump, it should read between 13.5 and about 14.8 volts once the rpms exceed about 2000rpm, and the car jumping its cables are disconnected (if you jumped the car) if the battery is reading less than 13 volts, with the engine rpms at 1700-2000rpm, or so the alternators a strong suspect , as the defective component, but the battery may be defective, if the battery won,t take an over night trickle charge to 12 plus volts its most likely trash, and pulling the alternator voltage down.

do some research, ask detailed questions, make sure what you buy is a direct bolt in version,for YOUR APPLICATION, but if you need to replace the alternator do yourself a favor, and yes pay a bit more and get a 150-200 amp alternator (you might have to upgrade the gauge of one or more wires in the car between the alternator and battery, to get the full benefit)
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Staff member

he just called me and said he talked to the guys at summit racings tech dept, he did a few tests, and found the alternator was as I suspected dead, and ordered this 200 amp alternator as he found the original factory alternators dead (keep in mind its 20 plus years old now) and he has noticed the 200 amp alternator in both my corvettes and has heard me talk about why I chose to upgrade



so the story continues

Ive purchased several 200 amp alternators from the guys at ... ageSize=60 ... -1993.aspx ... t-101.aspx's/PMappGuideEbook.pdf

and Ive also had several minor NON_RELATED electrical issues with alternators and electrical drains that they were very helpful in diagnosing, the main thing youll want to do is install a new direct connection, 4 gauge power lead from the new alternator to the batter positive terminal.
youll very likely find that your engine runs cooler and your fans run much more efficiently once they can get all the current they want, youll also find the ignition spark is much brighter if you get the same results Ive seen every time.
Youll also want to make very sure your electrical grounds are solid and think thru your ignition instal, most MSD control boxes fail due to heat or moisture, mounting them in a reasonably cool dry location helps and that ELIMINATES inside the engine compartment,mounting the controller in the upper most possible location in pass side foot well as far up under the dash as you can mount it is a frequently suggested and used location

Vaughn said:
You want to mount it using these criteria:

1. It needs to be relatively cool.
2. It needs to be away from road debris.
3. It should be relatively close to the coil.
4. The wire harness needs to be relatively short.
5. It should have an EXCELLENT ground and power supply. Ground and power supply are CRITICAL for best performance.

You have to make certain that the grommet is in place and is unlikely to allow wear on the wiring harness. If it is mounted inside the passenger compartment, make certain that it has sufficient airflow around it to make sure it won't overheat.













I make this info stuff easy to find ... -Coil-Tech
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solid fixture here in the forum
what would constitute a tune a up in an lt1? i mean theres only so much adjustment to be made in the way of idle characteristics... just plugs and wires and some filter changes? im sure my 96 could benefit from that and more


Staff member
well his alternator arrived from summit yesterday, and he called, too tell me, I asked if he needed help
(its a rather simple job, just remember to disconnect the battery before you install the alternator to reduce the chances of it being damaged during the install of course!)
and I got the answer I expected, that he would love to have me stop by for a few beers or coffee but he was not 100% sure he was up to getting involved with the alternator install yet!
while I and I'm sure everyone else has days when working on the car seems to be more of a P.I.T.A. than its worth, its such a quick and simple process I don,t think Id be that reluctant too jump in and get it done! but I'm fairly sure he will install it later today


The Front Frame Rails on C4 Corvettes do swallow bolts if dropped Grumpy.


Staff member
I just got a call I was rather expecting, it seems the current owner of a certain corvette is really shocked at how much smoother the engine runs now that theres a 200 amp alternator installed... a common reaction I hear a good many times but it seems you need to experience the difference before most guys notice that the old alternator BARELY worked to provide the cars electrical needs
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