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Old 01-12-2018, 10:56 PM   #1
RedBed
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Temp Gauge



I've read all the threads and I guess I'm just not getting it.

Brand new temp gauge in dash. Tested it by grounding green wire, it pegs.

New sending unit, no teflon tape, clean threads - 2 so far, AC Delco 8993146 (probably wrong) and BW WT358 .

Block grounded.

Checked continuity between body of sender and block - good.

Weird - also continuity between body of sender and it's blade...?

Still, it doesn't move.

(Previous owner had an aftermarket gauge in the same spot, it worked fine, I am trying to get it back to stock gauge.)

Any suggestions?
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Old 01-12-2018, 11:41 PM   #2
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Re: Temp Gauge

Maybe both sending units were wrong? AC Delco says OEM for 305 was 213-4792.

?
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Old 01-13-2018, 08:13 AM   #3
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Re: Temp Gauge

Someone did a big right up on this subject awhile back. And it has to do with the temp sensor. The way I understood it, you almost have to have an OEM sensor. The aftermarket sensors don't jive with the gauge.
My truck still had all the original gauges, but the PO had put in an aftermarket sensor & gauge in. I wanted that all out, didn't like the gauge mounted to the dash. Well long story short, I found the correct sensor and installed it. Hooked the wire back up to it, it was still there. The original gauge still worked. Not sure why they ever changed it to an aftermarket on in the first place.

Let me look around and see if I can find the thread.

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Old 01-13-2018, 08:26 AM   #4
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Re: Temp Gauge

Found it: http://67-72chevytrucks.com/vboard/s...d.php?t=703349

On my last post, there is a link to another thread. Rich Weyand & Hatzie are the ones that are knowledgeable in this dept., and they both have links to other other threads or info. This should help you get squared away. I found this thread before I replaced my sensor, so I din't have any issues.
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Old 01-13-2018, 11:49 AM   #5
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Re: Temp Gauge

This is it.

I did order the 213-4792 that ACDelco says is OEM. I guess we'll see.

I see that most are mounted on the side of the block, but this is where mine was mounted when I got it, but like I said, it was an aftermarket.

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Old 01-15-2018, 05:33 PM   #6
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Re: Temp Gauge

Well now I'm just pissed.

3rd temp sensor, and nothing. According to ACDelco, the OEM sensor.

Could it just be from being mounted in the manifold and not the block? It seems to be getting plenty of heat mounted in the manifold, don't see how that would be it, but who knows..?


...help...
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Old 01-15-2018, 06:08 PM   #7
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Re: Temp Gauge

Sounds like you have a wiring issue. In simple terms, all those sensors are is a heat sensitive resistor. The more the circuit is closed (or opened), the more the gauge will move. If you say the block is well grounded to both the body and the chassis, and the sensor is well grounded to the block, then I would be checking continuity from the sensor wire to where it connects to the gauge cluster. If the wire and the circuit board for the gauges checks out OK, check to see if the gauge cluster has a proper ground. I believe this gauge also has a 12V feed, iirc. If the ground and power to the gauge is also good, then the gauge would likely be faulty.
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Old 01-15-2018, 06:47 PM   #8
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Re: Temp Gauge

Quote:
Originally Posted by Nick_R_23 View Post
Sounds like you have a wiring issue. In simple terms, all those sensors are is a heat sensitive resistor. The more the circuit is closed (or opened), the more the gauge will move. If you say the block is well grounded to both the body and the chassis, and the sensor is well grounded to the block, then I would be checking continuity from the sensor wire to where it connects to the gauge cluster. If the wire and the circuit board for the gauges checks out OK, check to see if the gauge cluster has a proper ground. I believe this gauge also has a 12V feed, iirc. If the ground and power to the gauge is also good, then the gauge would likely be faulty.

Ok, but if that is the case, wouldn't that keep the gauge from pegging when I ground the wire that goes to the tab? I did test it that way as well.

Sure wish I could find a pic of the back of the instrument cluster. I dread pulling that apart again. Just had the truck interior gutted for a few weeks and it's almost back together. :-(
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Old 01-15-2018, 07:19 PM   #9
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Re: Temp Gauge

I went out and jammed my phone up behind the dash and took some pics. Anybody know which plug/cluster has the temp gauge wire in it?

1


2


3


4


5
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Old 01-15-2018, 07:27 PM   #10
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Re: Temp Gauge

I'm going to look in my manual here in a moment, but is it possible that you're using a coolant temp SENDER instead of a coolant temp SENSOR? One is meant for an idiot light, the other works with a gauge.

Edit: Manual shows #35 Dark Green at the cluster connector as being the signal wire from the sensor.
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Old 01-15-2018, 07:35 PM   #11
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Re: Temp Gauge

Aftermarket senders are notorious for not matching the OEM resistance curves. Where did you get your new gauge? If it is also an aftermarket, even if it is designed to fit in the OEM cluster, it could also have a non-OEM curve.

The early OEM gauges had a lower resistance curve then the later ones. So a late curved sender paired with a early curved gauge will result in almost no movement, even at full hot.

When you do your ground test, are you grounding to the side of the sender, also testing the sender ground?

I played this game. Finally found a combo that sorta works. A sender O'Rielly's says is for a 89 Suburban paired with a mid 80's gauge works close. Not perfect. Rather sensitive to outside temps. If it is cold out, the gauge will read about 1/4. If hot out, will read about 2/3. But better then I had for years.
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Old 01-15-2018, 07:37 PM   #12
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Re: Temp Gauge

I was going to say the dark green wire too. That's the one that's hook up to my sensor
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Old 01-15-2018, 08:09 PM   #13
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Re: Temp Gauge

Bought a 213-4792 AC Delco. Engine Coolant Temperature Sender

AC Delco website where I got the number:

http://parts-catalog.acdelco.com/cat...log_search.php

Before that, AC Delco 8993146, BW WT358

This is the Gauge - from ClassicParts - https://www.classicparts.com/1973-87...info/24%2D843/


This one, right?
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Old 01-15-2018, 08:26 PM   #14
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Re: Temp Gauge

Yes that's the dark green wire.
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Old 01-15-2018, 08:33 PM   #15
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Re: Temp Gauge

Thanks

I know there are 3 posts on the Gauge. Anybody know what other 2 wires correspond to the other 2 posts? And what they are?
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Old 01-15-2018, 08:39 PM   #16
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Re: Temp Gauge

A wiring diagram is what you need. A member, Hatzie. Has all of them on this link. Find your model year, this should help

http://67-72chevytrucks.com/vboard/s...&highlight=PDF
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Old 01-15-2018, 08:45 PM   #17
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Re: Temp Gauge

This is the description of the BW WT358 sensor you have listed:

Quote:
Temperature Sender With Gauge; In design, BWD specifies custom wax formulations that will expand when heated, activate a snap action electrical contact and transfer the electrical signal to the fan controller. In manufacture, BWD custom form the wax pellets for different temperature range specifications. All units are calibrated & tested to confirm switch actuation at their specified temperature. The switch is designed using a formed bimetallic contact arm. The bimetal contact movement is achieved using the different expansion rates of two metals fused together. This is a creep action device, provides precise performance. In production, all thermal switches are factory-calibrated to make electrical contact at the specified lower-temperature set point. BWD switches feature a robust design with high grade materials to meet the stringent demands of today's service professional. BWD is a global manufacturer of original equipment ignition products, complete quality control is maintained through the manufacturing process from componentry to finished product.
Sounds to me like that specific sensor is intended to control a fan circuit by the way their description is worded.

The 213-4792 AC Delco sensor is coming up as a gauge sensor, but it also shows that fitment is 1985+ Chevys, which may not be compatible with your gauge, and thus why you might not be getting a reading from it.

The AC Delco 8993146 appears to be correct for 1979 and later gauges, and I do realize that you have a 1979, but that was also a crossover year for gauges and you may have late 78 gauges and wiring in your truck. You may need sensor 1513321 if this is the case.
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Old 01-15-2018, 08:46 PM   #18
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Re: Temp Gauge

Quote:
Originally Posted by RedBed View Post
Thanks

I know there are 3 posts on the Gauge. Anybody know what other 2 wires correspond to the other 2 posts? And what they are?
You should have +12V on one post, a good ground (<1Ohm) on another post, and the third post should lead out to the sensor (green wire).
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Old 01-15-2018, 08:59 PM   #19
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Re: Temp Gauge

Ok, when the dash cluster was off and the gauge was out, I did test the posts and did show 12v when I went from hot to ground post.

So I guess the next thing to do is maybe jump into the Dk Green wire at the connector, run it through the firewall and connect to the sensor and see if that works. Yes?

I do know that from the firewall forward, there is continuity to the end of the wire at the sender.
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Old 01-15-2018, 09:06 PM   #20
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Re: Temp Gauge

I would pull your cluster and test the dark green wire with an ohmmeter, one test lead at the cluster connector, and the other at the sensor connector. If there is an issue with high resistance or no connection, then obviously correct it (firewall connection might be an issue), but if there is little to no resistance in that wire, then either your sensor is faulty, the gauge is faulty, or they are mismatched in resistance values. You mentioned earlier that your gauge pegs when the sensor wire is grounded, which indicates your gauge is working. At that point, I would suspect either a bad sensor, bad ground on the sensor (teflon tape can cause grouding issues. Use PTFE paste instead), or the sensor is functioning but has a different resistance range than the gauge and is not compatible with it.
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Old 01-15-2018, 09:35 PM   #21
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Re: Temp Gauge

Well I jumped a wire into the connector under the dash, and out to the sender, and nada. I rechecked continuity between body of sender and manifold and ground is good.

I guess that means maybe I need to try sensor #4 - the 1513321 (aka G1852) ?

AAAARRRRGGGGHHHH

I REALLY appreciate the help.
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Old 01-15-2018, 09:49 PM   #22
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Re: Temp Gauge

I would give it a try if you have one available locally or can get your hands on one easily enough. Who knows what has been changed or altered on the truck in nearly 40 years!

Also, if that gauge is a reproduction part, you might try contacting the manufacturer and find out what they specify the resistance range is to operate the gauge. It might make it easier to find a sensor that matches that value, instead of guessing what works.
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Old 01-15-2018, 11:31 PM   #23
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Re: Temp Gauge

Part of your problem could well be the Classic Parts gauge. There is not a single temp gauge that will work with the OEM sensors across the entire 73-87 range. There are at least two different resistance curves in play. You should call Classic Parts and see if they sell a matching sensor for their gauge.
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Old 01-16-2018, 10:36 AM   #24
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Re: Temp Gauge

The OEM and aftermarket equivalent senders will drive the gauge needle no matter the exact thermistor resistance curve. The differences are exactly where the needle ends up at various temps.

You shouldn't install the sender in the intake coolant crossover. Use the LH or, in a pinch, the RH cylinder head TEMP sender location.

The sender should work in the intake crossover but it will not work properly.

Let's back this train up and look at the behavior.
  • The gauge nails at HOT when you short the sender wire to ground and drops back to COLD when you remove it from ground. This means the TEMP gauge wiring is A-OK.
  • If you want to test the gauge get a 1/2W 100Ω resistor and put it between the TEMP wire connection and ground. This should drive the needle over but roughly near the mid-point... . If it does the gauge works OK.
  • The sender body to engine resistance is 0Ω or darn close so you haven't electrically insulated the sensor from the engine.
  • At operating temp the engine should be between 190 & 220 so the resistance from the wire tang to the sensor body should VERY ROUGHLY be between 130Ω & 90Ω. If it is then the gauge is probably at fault. If it's not even close... The sender is at fault.

You can download both 1979-1984 parts catalogs from the manuals thread and find the "correct" GM sensor part # for your truck in the illustration book. Either of these sensors will work as long as the threads are the right size for your head or you have a 3/8-18 x 1/2-14 brass bushing.
1979-1980 CK...8993106...1/2-14 threads Coolant TEMP exc. 250 & Diesel
1979-1980 CK...8993164...3/8-18 threads Coolant TEMP 250 & Diesel

8993146 is for 1983 G, 1979-1984 P, and 1982-1984 CK. THIS WILL DRIVE THE GAUGE... if it's working.
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Old 01-16-2018, 12:44 PM   #25
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Re: Temp Gauge

Spoke to classicparts.com and asked them if they could tell me what sensor went with the gauge they sent me, and the only info they could give me was for the one they sell, which is their part number.

So I peeled back the sticker on their box, and under it was the distributor of the gauge (counterpart automotive) and called them, and they told me AC Delco G1852 was the right sensor.

So I ordered it and have my fingers crossed.
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