The Stovebolt Site Forums The Shop Area The Electrical Bay '58 Temp Gage Wiring Question

I experienced overheating in my 235 equipped '58 so I decided to start small and work bigger. I replaced the thermostat, had the radiator pressure/flow tested, replaced the sending unit, and bought a new temp gage. While purchasing the temp gage from Chevy Duty, I went ahead and bought a "cluster decal kit" ($6) so that the Amp/Oil/Gas gages wouldn't look like 48 year old gages when compared to the brand new temp gage. I ran into some trouble and once again need to rely on my Stovebolt contacts for help:

The old gage, which was the original I believe, had a single post on the back. Granted, it was broken, and if there was another terminal, it was no longer part of the assembly. The new gage has two posts. I looked at the wiring schematic that is in the shop manual and I'm completely unimpressed. It doesn't show me any real information that I can use, such as wire color. I made a huge mistake and connected a stray red wire to the left (outboard) terminal of the gage, and the previously-connected green wire (from the sending unit) to the other terminal of the gage. As soon as I powered up by turning the key to ign, I got all kinds of smoke, stink, etc. I'm certain I cooked that dang brand new gage as soon as I turned the key. (There are resistors in the new mechanism and I doubt these could withstand such stupidity.)

After messing with it for a while, I finally pulled my head out of my derriere, and disconnected the red wire altogether. Lo and behold, the other gages began working correctly and the arcs stopped.

My question is: given two termimals on the back of the brand new temperature gage, what is connected? I tend to think I should only connect a green to the terminal on my right hand side (closest to the steering column.)

What is the other terminal for?

When I connected the stray red wire to the gage, the Ammeter and Gas gages stopped working and the red wire's insulation melted.

Please help with any experience you may have to offer. My engine is dependent upon me knowing the temperature, and I know that I must order another unit, but I'm reluctant to install it until I know what I did wrong.

A word of caution to those of you considering ordering a temp gage from Chevy Duty: I ordered a gage for a 1958 and coincidentally ordered a cluster decal set to update the look of my Amp/Oil/Gas gages. The gage provided, even though it is labeled '55 - '59 in the catalog, is for a 1955. It has only three dots (low/med/high.) I had to install a '56 - '59 decal over a brand new gage to make it look correct for 1958 (low dot, normal temp line, high dot.) I'm a little miffed at Chevy Duty for using the '55 for all years '55 through '59 without letting me know. I had a fix THIS time, but when I get my new gage to replace the one I fried, I'm going to have to move the decal. If I didn't buy the decal, I'd have an incorrect '55 readout.

Bill

one wire [green] goes to the sender, which is the ground side, the other side [pink] gets power from the ign sw - the pink wire goes to the driver side/green wire to the passenger side - don't know about yer shop manual, but mine has colors, they're just a little hard for poor eyes to follow and are set in odd places with arrows pointing to the wire

the gas gauge also gets power from the ign sw, and the other side to ground thru the sender - ammeter has a black wire to the starter, heavy red wire to the ign sw and the light sw both

that red wire must be a hot wire from the ign sw or light sw or fuse panel that also supplies the other gauges and hooking it to the temp gauge is grounding it [obviously, given the smokey melt ] - sounds like you need to go thru the wiring - try a magnifier on the diagram, it'll all come clear - and find out where the other end of that red wire goes, randomly hooking things up don't work well

also the 3 dot gauge isn't just 55 - of about a dozen gauge sets I have, roughly half are 3 dot, the others are the 2 dot w/ the center line, and I haven't parted but 1 55 - change may have actually been 58/9, and 5-7 was what all the repro parts were made for, 8/9 only recently started getting it's own parts recognized, like the headlite doors/fenders/park lights

if you need a better wiring diagram, I've got a scan of mine I'll send ya

Bill

It seems to me the 235 had the capillary tube type gauge. That might explain the single term. It could have been broken or cut off.

Red58 is correct on the guage markings. I pulled a cluster from a '56 3600 and the guages match the '55. Sounds like a mid-year change to me. I've also seen 235's both ways on the temp guage, the '56 that I took the cluster from had a 235 with the electric temp guage. Maybe they used what they had on hand to keep production up.

My '49 GMC came with an electric temp gauge rather than the capillary tube like Chevys. Power for the temp gauge head is a short jumper from the power side of the fuel gauge. Two related questions... (1)I'm running a '54 Chevy 235 in the GMC and was wondering what the first year was Chevy used electric sending units for the 235, and (2)would it be appropriate to put an inline fuse between the sender and the gauge (and if so what amp fuse)? Thanks in advance.

I believe the 55 1st was electric, but it was by 55 2nd for sure - doesn't metter tho, if you've got an electric gauge, just switch to an electric sender - no on the fuse, will do nothing

Bill

Thanks a million for the informative replies. I know that what I NEED to do is put in a new harness. This information will help me to keep going until I get the nerve to tackle the problem technically and financially.

I think I'll jump power from the gas gage to the temp gage if I can't find a PINK. (Over time, those wire colors have faded- green is pretty dang dark, red has gotten lighter, etc.) That way, I 'll KNOW that it's right, and not a hot. All my other gages work okay, so this is probably a safe option for now.

Good info on the line vs. dot gage appearance. I didn't consider that it could be a supply issue or possibly even a location issue. Maybe my truck's factory (KC) used line when others had dots, etc.

I feel comfortable enough now to order a new gage. I can't wait to get it all in!

Mucho appreciado!

Bill

I have the original temp gage in my 58 and it is all dots, and I have an electric sender. The wiring diagram that came with the shop manual is darn near impossible to read, but I got a better diagram through a link at another sight (Chevytalk.com, I think). If you like, I could send it to you.

Got to checking the shop manuals, the '55 only shows the capillary tube type, '56 and later shows electric. Having said that, I have seen later 6 cylinder trucks with capillary tube guages and electrics. However, I beleive that v-8's may have used electric temp guages on all built after '55. My '55 had the capillary tube guage.

Lumbergh, I'm glad to know that I'm not the only one having trouble reading a shop manual. It isn't the technical things that are hard to make out, it is the size of the text! Sheesh! I've never seen 2pt font before...and I'm not all that sure I'm even seeing it now.

If you don't mind, I would certainly like to have a link or an electronic rendition of a '58 diagram. My email is ksy503 at yahoodot com.

Thanks!
Bill