New water temp guage install and problem...
 

I installed an Autometer electrical water temp guage to supplment the stock boost gauge this weekend. I installed the temp sender in the thermostat housing as recommended. If you don't have a 6" extension for your socket driver, just go buy one or you will never get the bolt near the airpump off.

My problem however, is that the temp guage does not appear to be reporting the correct temps. I turned on the car to check it out and it immediately jumped to abour 150 then continued to rise and leveled off at what would have been about 260. The stock guage worked as it always did starting off at 0 and then moving to just below center.

I know the stock gauge isn't the best, but I have a hard time believing it would hang around center with temps at above 250 degrees.

Any suggestions as to what may be wrong here? I wired to the sender using 18 guage wire and spade terminals. The ignition wire is tap spliced into another wire jumpered directly off the fuse box and the ground is tap spliced into the ground wire that I found running along the A-pillar.

Thanks!

Thats what you get for buying a piece of junk autometer guage... I would return it and either ask for your money back to go buy a real guage or ask for a replacement.
I've installed 5 of these at work in the past couple days.. 2 of them came back with problems...
I know try and steer customers away from these crappy products..

Is there anyway to test if the gauge is working appropriately? Before I send the gauge back i'd like to make sure it's not something else.

I am pretty certain I installed the sender appropriately though. It's got contact with the thermostat housing so it is properly grounded there and does extend into the housing enough to get the sender tip into the flow.

The gauge moves as the car heats up, it just looks like it is always +80 degrees too hot. It's a relatively hot day outside, so I wouldn't be surprised if the coolant temps were ~50-60 degrees with the car off which would explain why the gauge started at 140 or so.

When you first start the car, where does the gauge sit?

This is exactly what happened to the other guages... It's almost like they weren't attached properly from the factory or something...

What type of Autometer did you get. What I mean was did you buy their bargin basement guages? Their high end guages have always worked well for me in the past.

I bought the autometer ultra-lite boost and water temp gauge.

I don't think it's the bargain basement line, at least I hope not.

When I first turned on the car from completely cooled down it was reading around 140 and I know there is no way for that to be correct. I believe these gauges work by the varying resistance to current cause by change in temperature so I am wondering if there is anything special that needs to be done for wiring the sender.

I used the manuals instructions for 18 gauge wire and installed some spade clips on the ends to connect with just like I would for any other electrical hookup. I assume thats what everyone else has done (but I couldn't find any instructions on the actual wiring of the sender as it seems like it's just assumed thats how you would do it).

Given SAiamNE is having the same behavior, I am wondering if the gauge might just be broken. I just don't know how to check that.

The boost gauge works just fine.

get the new D"EFI bf gauge man its well worth it and looks stock if you get them in amber, this is a very very good company and fast
http://cgi.ebay.com/ebaymotors/DEFI-...QQcmdZViewItem

Those look pretty trick, but $170 for just the gauge? Maybe after I get the rest of the reliability stuff done. In the mean time I just need to get this one fixed or send it back if it's broken.

Doesn't sound like the gauge is broken (all it does is read signals from the sender). Sounds like either the sender is getting grounded out or the wiring from the sender is damaged.

Can you take a pic of where you mounted the sender?

I agree with Mahjik. Probably wired improperly. You may need to ground the sender.

My autometer water guage did the samething. I called Autometer and they said the sender must be bad or grounding out. They sent me a new sender free of charge and it works perfectly now!

I installed the sender in the same spot suggested on robrobinette.com from this image...

http://robrobinette.com/images/water_temp_hole.jpg

Not where he tapped it, but the red location titled "Or here." It would basically look exactly like that if I took a picture minus the AST elimination work.

When you say the sensor is "grounding out" what exactly does that mean? The instructions I read suggested putting teflon tape around half of the threads but letting the other half of the threads and the sender make contact with the housing in order to ground it. I am 100% positive it is making contact with the housing, which should be ensuring that it is grounded.

If the problem is in fact that the sensor is not grounding, I should be able to fix that by running a wire from the sensor to the engine block or other ground correct? I can give that a try.

My guess was also that I either wired it incorrectly or the sender was bad given that the gauge is functioning and raises temp as the car warms up, it just always seems to be X amount of degrees too high (which seemingly suggests its encountering too much baseline resistance).

Any other suggestions on things to try?

Thanks again for the help figuring this out.

Try using a variable resistor inline with the guage wire and with key on turn the resistor until the guage reads at zero. This is what I had to do after installing a new electrical temp guage in a mach 1 stang to get the needle to sit in the correct position. the guage is probably good, it probably isn't getting the proper resistance or ground that it needs to read correctly.

I have had zero problems with my autometer temp gauge. My bench mark being fans set to come on at 180. Happens everytime the gauge hits 180. I have the classic chrome mechanical gauge. I like to try and keep it close to stock looking (even if the bezell isn't exactly the same).

I third this. Try these and get a new sender if they dont work.

If you do end up sending it back and can choose another guage....FWIW I'm happy with my DEFI 'D' series (~$115). Seems to be reasonably accurate, but I used the TB coolant line for the sender. It also looks nearly stock, especially at night.

^ I second that.

After doing a bit more reading on how coolant temp gauges and senders work, I am almost certain that the sender either has to be poorly grounded or bad, and I am pretty certain it is grounded properly.

I am going to try removing the sender wire and grounding it to the engine block which should drop the gauge to 0. That would eliminate the wiring as a concern. I figure if I remove the sender and ground it directly it should do the same thing, if not it must be bad.

Given that it does not appear exceedingly rare for a temp sender to be malfunctioning, that seems to be the most likely source of the problem.

Any flaws in that line of logic?

Don't listen to all these schmoes telling you it's an Autometer and it doesn't work because it's crap; they don't know wth they're talking about. No matter how much you pay for a guage they all use the same cheaply made senders and $150 gauges do not magically fix wiring problems.

You either have the sender wired wrong or you have the wrong sender.

First make absolutely certain you have the wiring at the gauge end correct. After that verify that the sender is installed correctly. Grab a volt meter and verify that the body of the sender shows continuity to ground. If it doesn't, there's your problem. If that checks ok make sure the signal wire from the gauge is not shorting to the chassis.

It's also possible you have the wrong sender for your gauge. The senders have different levels of resistance and are meant to work with the proper gauge. If you had the wrong sender you could get readings that got hotter and cooler but they would always be out of whack with what the actual degree markings on the gauge face are.

If with a cold motor you turn the key on and get any reading at all on the temp gauge you either have the wrong sender or a wiring mistake.

"If with a cold motor you turn the key on and get any reading at all on the temp gauge you either have the wrong sender or a wiring mistake."

That's definitely the case. Just turning the key to the accessory setting gives back a reading of 110 degrees. So as you stated, something definitely has to be wrong with the wiring or the sender.

I will take a volt meter to it and see if the sender ground checks out.

I've checked and double checked the gauge and the wire running through the firewall so I'm fairly certain the problem is not in the wiring. I can always check again if the sender appears to be O.K.

With any luck it will just be a simple grounding issue, if not it looks like I am returning the sender for a new one.

Thanks DamonB!

I took a continuity tester out and ran some tests on the car.

1. The wiring running from through the firewall is not shorted against anything. It shows no continuity when removed on both ends.

2. The sender installed in the thermostat housing shows a strong circuit where the sender contacts the housing.

3. The sender shows a weak circuit at the tip where the wire connection should be made.

When the sender wire is grounded to the engine block the gauge will pin at max when the key is placed in the ignition and turned to the accessory position. When the wire is placed on the sender tip, it reads at ~150 on a 100-250 gauge. With the sender connection is disconnected at the sender, the gauge stays at min.

This makes sense as the sender housing is insulated from the sender connection point and wired together through a thermister as I understand it. As the coolant heats up the sender the resistance drops and a strong connection is made increasing the reading on the gauge. Thus the gauge pegs when grounded to the engine and a perfect connection is made, and has no reading when no connection can be made.

So the question is, is the sender bad and allowing too much of a connection below 100 degrees, or is the gauge bad and have too low of a voltage threshold allowing it to take a reading below 100?

In either case it appears the wiring is just fine and either the sender or the gauge is bad. Looks like I will be calling autometer

Am I missing something critical here that makes that incorrect?

Onyxjl, I bet you were accidently supplied the wrong sender. Good job troubleshooting the wiring.

That appears to be the case. Autometer should be sending me a new one shortly and hopefully that fixes it right up.

Fortunately, removing the sender is a hell of a lot easier than installing it the first time and can be done in about 5 minutes.

For anyone reading this that is thinking about doing the install, the other guides and FAQs I have found are not exactly clear about the actual process so here is a quick run through...

You don't have to remove the intercooler, battery, AST, or airbox to remove the thermostat housing. Plan on about 3 hours to do it, it took me longer but I ended up taking the long route because I had intially thought to just drill it while it was on the car. That will probably take you longer than removing the housing.

You must have:
Large pair of pliers or vice grips for the pinch clamps.
Flat head and phillips head screw drivers.
10mm socket.
6" socket extension
Socket driver
Coolant to replace what you drain out.
And the appropriate drill/tap for your sender size. I ended up having to get a 1/8 NPT tap from Napa as Home Depot does not carry one by me.

1. Drain the radiator a little bit to lower the coolant level.
2. Loosen screw clamps for intake hose leading from IC to the tube leading to the throttle body and remove hose.
3. Loosen both screw clamps for the coupling connecting the pipe for the turbo to the hose connected to the bottom of the IC. Remove the coupling, not the whole pipe assembly connected to the intecooler. You can, but you dont have too.
4. Loosen the pinch clamp on the water hose running from the Thermostat housing to the AST at the housing and remove hose. Expect some coolant to leak out.
5. Loosen the pinch clamp holding the intake hose to the side of the airbox and remove hose.
6. Loosen pinch clamp holding coolant hose to the bottom of the housing and remove hose. Expect to lose a bunch of coolant. Stuff a rag into the top of this hose to prevent bolts and other parts from falling in.
7. Loosen the screw holding the pipe assembly at the bottom of the intercooler a bit so that you can either remove this whole pipe, or just turn it to the right a bit and get it out of the way.
8. Unclip the wiring for the sensor on the front of the housing.
9. There are 3 bolt holding the thermostat housing onto the engine. Two are on the right side of the housing toward the middle and bottom. The third is on the left side near the airpump and behind the drivebelt. Hard to see without a flashlight. The first two come off fairly straight forward. To get the third you need to push the drivebelt down a little to get the socket back to the bolt. You should be able to get in there with a little patience and the 6" extension.
10. Rock the housing back and forth a bit and it should pop right off. More likely you will end up yanking it off a lot harder than you needed too.
11. The next two steps will get aluminum shaving everywhere. There are two flat round circles on the front of the housing, pick either one as your drill/tap spot. I picked the one that was a bit more recessed. Drill straight through this section, and don't worry too much about drilling too far just be aware of what you are doing.
12. Tap the hole you just drilled.
13. Flush out housing to remove all of the shavings.
14. Install sender into housing. Don't over tighten. Now would be a good time to check that the sender has a good ground to the housing with your continuity tester.
15. Reverse steps 10 through 1 using some liquid gasket to seal the housing back to the engine.
16. Add coolant back to the engine and check for leaks.

As for the wiring, there are already plenty of other good walkthroughs on this so I won't repeat that except to say it will probably be much easier for you to run the wire through the firewall from inside the car before installing it onto the sender. I went through the edge of the large rubber grommet around the steering wheel.

https://www.rx7club.com/showthread.p...ghlight=sender
TB coolant line works well too. :)