The Stovebolt Site Forums The Shop Area The Electrical Bay temperature gauge question.

Hello, I need help. The temp gauge in my 66 gmc is malfunctioning or maybe the sending unit. It reads cold for about 2-3 minutes and then moves rather quickly to the hot side (after starting). I just put a new 283, turbo 400 and painless wire kit. I have 2 gauges and 2 sending units and I get the same results from each. The gauges seemed to pass the test I used. Any help would be appriciated. :confused: Jeffrey.

have you checked the temp in the rad? new thermostst? not in backwards? new engine workin well?

Bill

Well I pulled the thermostat, it was new and installed right, I ran it and it took the gauge a little longer to swing over. I put my hand on the radiator and the intake (aluminum) manifold. they were warm but not hot, didnt burn at all. Mabey its the senders? There after market I guess.

While you have the thermostat out, put it in a pan of water on the stove to insure it is opening correctly. Use a themometer to check the temps of the radiator coolant with and without the thermostat installed. Are you using a 50/50 mixture? Is the guage pegging to hot side or just higher than what you think it should be. What range thermostat are you using? 160 degree should be sufficient for summer driving.

It pegs hot side even when temps are around 120 degrees. It moves the gauge as soon as it just starts to warm, waterpump,radiator,therm all new and working. dosn't matter if thermostat is in or out. thanks for all your guys advice,if you have any more i'll take it. Jeffrey

you may have the wrong resistance sender - the proper sender for a 66 283 should be available from NAPA or similar places, but the GMC gauge may be different than the Chevs, and I only find all 6cyl's listed for 60-66's, so maybe you should try a sender from a 230 or 250 if it'll fit - otherwise it has to be in the wiring someplace
edit - just had a thought - if you have the sender wire in the "stock" clips along the valve cover, make sure you didn't damage the plastic coating enuff that it's shorting as it heats up - the temp circuit all depends on resistance to ground

Bill

Thanks again, I checked resistance on the senders and got 2 different readings. Does .290 ohmk and .563ohm k sound right? :rolleyes: Jeffrey

I have the same trouble with mine, and
I think my sender is wrong.
A little while back I changed the entire coling system (with a 180 thermostat) and installed a mechanical temp guage.
THe truck has been stable at 180 for months, so I reinstalled the electic sending unit.
BAM! Right to full hot when it warmed up.
Off to the parts stores to deal with blank looks from some of tomorrows leaders.
"A what...for a 1965? That isn't in the computer.."

Yep, I threw away the origional sender for the v6 305, I still have the gauge and it used to work, I'm leaning towards the sender not having the right resistance. I saw some on the net that are origional specs.

I'd expect NAPA to have the V6 sender - worth a try - and the 350 as well crowbar

Bill

The next stop , napa or ? I'll let ya know what happens. Thanks jef :confused: frey

I went to O-O-O-O'Reillys last night and picked up a WT230 temp sender.
It was listed for the '65 283.
Cost less than five bucks.
I haven't put it in yet, (darn work gets in the way of fun), but will post up when I do.
Thanks,
Mike

Problem solved, I had to go to wrecking yard and get a temp sender off a 1963 GMC pickup, it works great now i have 3 senders for something else. I called GM and they said they quit making the temp senders for the 60-66 GMC in 1980.

jeffery
Glad you got the problem solved but for others who have replaced their senders and/ or bought all new gauges the senders come w/ the new gauges. When replacing senders the usual standard Chevy thread is 1/2''npt. Many of the (new gauge) senders are 3/8''npt, so an adapter/reducer must be used to fit the new sender. This creates a ''dead zone'' (see my profile) around the sender. A good remedy is to use your lathe (or countersink on your drill and hacksaw) to cut down the length of the adapter threaded end and taper the inside of that reducer end so the sender's end is now in the flow of water. It just takes a couple mm. Also remember to use NO pipetite or teflon tape which causes grounding problems