LS Senders for C3 Gauages, err?

V

Vettezuki

Well-known member
Joined
Mar 26, 2008
Messages
141
Howdy,

Well, one of the dangling issues on my C3 is that the coolant gauge reads WAY higher than it actually is. This is apparently because of a mismatch between the sender from the engine and the stock 82 gauge. Anybody have any idea what the correct sending unit would be to use on my Gen III motor so my gauge will read the correct temp???
 
Couldn't you use the stock '82 gauge and buy an adapter to fit the head port? I assume you plan on reading off the passenger side head towards the rear, correct? I don't have any part #'s, but they do exist. LS1tech in the conversions section should have something.
 
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'82 had FI on it, so not sure if they changed the sender size or not, but the '72 gauge I had would not do with ANY sending unit I could reasonable find...so I had already changed heads to L98 aluminum, and went with aftermarket gauges, tired of the old antiquated crap...did my own panel...

:smash:
 
I would make sure that your gauge and wiring to the gauge will in fact read correctly given the correct signal from the sender. Easiest way to do that is go to Radio shack and buy a 2 pack of 70 ohm resistors for $1. Put one between your sender wire and ground and your gauge should read 220 degrees, put the 2 resistors in series making 140 ohms and your gauge should read 160 degrees. If your readings are close then your gauge and wiring is good if not your gauge and wiring might be the reason your not reading the right temp.
 
Thanks for the tips guys. I'll look into into and suck big2bird into helping me. :smack:
 
Is there a part # for an 82 sender that will screw into an LS engine?
 
I believe some have been turning down and re-threading the original senders.
lsisender.jpg
 
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greg75vette said:
That's what I read, but a lot of guys are going to adapters for simplicity.
Click to expand...

I looked hi and lo for a adapter, and found nuttin'....course the L98 heads are a 3/8? NPT thread....smaller then the '72 sending unit, but not the diff shown above...I DON"T THINK....

:gurney:
 
Well from what I understand, LSx's are fully metric, but I'd be damned if I knew the size. I haven't worried about gauges yet because I have bigger fish to fry before then (crossmember mounting).
 
greg75vette said:
Well from what I understand, LSx's are fully metric, but I'd be damned if I knew the size. I haven't worried about gauges yet because I have bigger fish to fry before then (crossmember mounting).
Click to expand...

I think the pic above is 12mm.
 
It would have to be. I'm simply mentioning that there other ways of skinning this cat. If I had the tools, I would probably turn it down rather than buy an adapter. However, I don't so I plan using adapters if the autometer sending units can be bought withthe correct thread and size.
 
Sorry I missed the update.

Apparently equis(?) makes adapter kits. However, some on LS1Tech say that puts the sender too close to the exhaust manifold?

Since I have a machine shop in the family I think I'll opt for that solution.

<begin potentially dumb question>
The sender is only connected to the gauge right? I obviously don't want to "send" a bogus signal to the ECM. I think, the ECM may get it's coolant temp from another sensor and the sender is just for the gauage but I'm not sure.
 
Vettezuki said:
Sorry I missed the update.

Apparently equis(?) makes adapter kits. However, some on LS1Tech say that puts the sender too close to the exhaust manifold?

Since I have a machine shop in the family I think I'll opt for that solution.

<begin potentially dumb question>
The sender is only connected to the gauge right? I obviously don't want to "send" a bogus signal to the ECM. I think, the ECM may get it's coolant temp from another sensor and the sender is just for the gauage but I'm not sure.
Click to expand...

Yes, like the FI on my '72 here with the old L48, the gauge was stock position in the head with the 1/2 npt sender, which I still have BTW...and the FI used it's own temp sender in the manifold....

later heads/engine, and the head hole was too small for the sender, smaller sender would not agree with the gauge, so I doctored the gauge, later went aftermarket, never found anythning to take a small hole into a large sender, no room anyway, headers.....

:bonkers:
 
I don't think the ecu reads temp from there, but I'm not sure where it reads the temp, if anywhere. I don't have a wiring diagram handy, so I couldn't tell you either. Let us know if you find out because I'm curious to know the answer myself.
 
greg75vette said:
I don't think the ecu reads temp from there, but I'm not sure where it reads the temp, if anywhere. I don't have a wiring diagram handy, so I couldn't tell you either. Let us know if you find out because I'm curious to know the answer myself.
Click to expand...

All ECU's I know of use their own temp sender....AFAIK they are/were independent of the gauges......
 
My $0.02........

I put the 68 temp sender (1/2 NPT) in the block plug of my LS motor. It wouldn't fit the small head bosses. I'm also using the 68 gauge. It's reading higher temps than the head, determined by aftermarket gauge and IR temp gun. Could be because of the location close to the headers.
The LS computer reads the temp from the drivers side front sensor. On the 98 camaro, a computer/gauge sensor combo is used. The rest of the years get gauge temp from the computer.
I want to keep the 68 gauge. So the data on the gauge resistance is below, so is my solution.

I got the following temp info for the 68 gauge from Willcox on CF.
temp/resistance
220/70
200/90
180/115
160/140
120/250
100/340
I measured the 98 camaro LS sensor below:
temp/resistance
192/215
181/272
157/428
135/675
105/1225
In addition, I've got an aftermarget (harbor freight) gauge sensor that's calibrated as follows:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98481
temp/resistance
260/70
200/140
185/210
165/280
150/350

A 250 ohm resistor in parallel with the harbor freight sensor gives nearly identical values to the original vette sensor. I used the adapter from these guys:
http://www.speedwaymotors.com/LS1-Water-Temperature-Sender-Adapter,8195.html
The HF sensor bound up on the adapter so I use a 1/8 NPT male/male and female/female to space it out.
 
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