Autometer gauges help

geostang351 · Apr 1, 2007

Took my Spring maiden voyage today to try out my Winter upgrades (New calipers and slotted discs - GOOD). New 4.11 trac lock rear in place of 3.00 open. GOOD. Front alignment WAY OFF - NOT GOOD! New gauges from Autometer NOT SO Good.

I had the car running for about 20 minutes. Oil guage topped at from initial start of 100 PSI, Fuel showed below empty(a t least 2 1/2 gallons in tank), temp bottomed out at 100* and never moved. All three gauges are set for 12V (remember after market and I "think" they required 12V and not 5V like stock). Why would the oil pressure top out and the other two bottom out? Ground is hooked up; getting power from Black/Green wire direct and not from CVR. Signal is coming from stock wiring. Using the oil pressure and temp units that were used when stock (did not use Autometer supplied sensors; shouldn't effect fuel). Any ideas?

66HertzClone · Apr 1, 2007

The sending units need to match the gauges, if I understand what you've explained, you left the old units in and connected them to the new gauges. If that's true, that's your problem. The senders and gauges work on a variable resistor, not a chance that the original Ford unit is the same as what the Autometer gauages are looking for.

When I installed the AM gauges in my car, I replaced the pressure sender and the temp sender with AM units, the fuel tank sender I did not have to replace. The fuel gauge from AM that I used can be calibrated to read different tank senders.

Did the gauges come with new senders? Mine did and the oil pressure sender has three wires.

bnickel · Apr 1, 2007

yes, you have to use the sending units that came with the gauges. autometer also makes different fuel gauges that will the stock resistance of you factory sending unit, you probably got the wrong one.

geostang351 · Apr 1, 2007

66HertzClone said:
The sending units need to match the gauges, if I understand what you've explained, you left the old units in and connected them to the new gauges. If that's true, that's your problem. The senders and gauges work on a variable resistor, not a chance that the original Ford unit is the same as what the Autometer gauages are looking for.

When I installed the AM gauges in my car, I replaced the pressure sender and the temp sender with AM units, the fuel tank sender I did not have to replace. The fuel gauge from AM that I used can be calibrated to read different tank senders.

Did the gauges come with new senders? Mine did and the oil pressure sender has three wires.

Mine did come with new senders I just did not put them im thinking I might not need to. Thanks for this info!

bnickel said:
yes, you have to use the sending units that came with the gauges. autometer also makes different fuel gauges that will the stock resistance of you factory sending unit, you probably got the wrong one.

I got the right fuel gauge (I think ). Calls for 13 ohms full to 75 ohms empty. This is what I require correct?

Any other ideas on this one?

JamesW · Apr 1, 2007

Autometers

Concur. I had the exact same problem when I installed mine. I was TOLD the OEM senders would be fine. Instead... the Oil Pressure pegged, and the Water never got up there. I had to order Autometer Oil and Water senders.

Are you running the correct Gas Gage for the older Fords? It should be the one that is 10 ohms full, 73 ohms empty.

geostang351 · Apr 2, 2007

JamesW said:
Concur. I had the exact same problem when I installed mine. I was TOLD the OEM senders would be fine. Instead... the Oil Pressure pegged, and the Water never got up there. I had to order Autometer Oil and Water senders.

Are you running the correct Gas Gage for the older Fords? It should be the one that is 10 ohms full, 73 ohms empty.

Yes I am. Still need to figure this one out.

reenmachine · Apr 3, 2007

Everyone's said it already, but you absolutely have to run the Autometer sending units. That will almost certainly fix the oil and temp issues. If you tell me the part number of the fuel gauge I'll tell you if it's what you want or not.

geostang351 · Apr 3, 2007

reenmachine said:
Everyone's said it already, but you absolutely have to run the Autometer sending units. That will almost certainly fix the oil and temp issues. If you tell me the part number of the fuel gauge I'll tell you if it's what you want or not.

The part number is 5815 for Autometer fuel gauge (2 5/16 size) Picture attached (not that this would help)

reenmachine · Apr 3, 2007

geostang351 said:
The part number is 5815 for Autometer fuel gauge (2 5/16 size)

That's the right gauge (2-5/8" actually) so you probably have a wiring issue. The needle only pegs when you're not getting power at all. Check the +12V and the ground. Even without a signal the needle will rise up off the peg a bit closer to the E. I just tried it with a cluster I have here on the bench with the exact same gauge.

geostang351 · Apr 3, 2007

reenmachine said:
That's the right gauge (2-5/8" actually) so you probably have a wiring issue. The needle only pegs when you're not getting power at all. Check the +12V and the ground. Even without a signal the needle will rise up off the peg a bit closer to the E. I just tried it with a cluster I have here on the bench with the exact same gauge.

That's what my gauge does; when power is applied by turning the ignition key, it sits just off the peg but just below E. I have applied 12V power to the S terminal and grounded the other and the fuel gauge topped off over full, so I know the gauge works. The old original gas gauge always worked so I'm guessing the sender is fine (and honestly, there is no way the car is 40 years old, then when I change the gauge, the sensor goes bad. That would be WAY to coincidental.)

reenmachine · Apr 3, 2007

OK, if the gauge is good, it's getting power and ground, and still no dice then there's something with the signal. That's all that's left. Do you have a multimeter you can use to measure resistance? If so, measure the resistance between the signal wire in the dash and ground. It should be somewhere between 76 and 6 Ohms depending on how much gas is in the tank. Make the same measurement right at the sending unit.

How did you wire the cluster? Did you use the original plastic main harness plugs and splice into the wires? Check this connection as well. Basically check the status of the signal wire anywhere you fooled with it.

geostang351 · Apr 4, 2007

reenmachine said:
OK, if the gauge is good, it's getting power and ground, and still no dice then there's something with the signal. That's all that's left. Do you have a multimeter you can use to measure resistance? If so, measure the resistance between the signal wire in the dash and ground. It should be somewhere between 76 and 6 Ohms depending on how much gas is in the tank. Make the same measurement right at the sending unit.

How did you wire the cluster? Did you use the original plastic main harness plugs and splice into the wires? Check this connection as well. Basically check the status of the signal wire anywhere you fooled with it.

I originally checked the signal and was reading 85 ohms at the end of the wire, furtherest distance from the tank as it got to the gauge (I thought the tank was completely empty but it wasn't as I filled it to the top with only 5 gallons). I'll try the resistance as the wire leaves the tank. Maybe the wire is so old it is at a higher resistance now due to age

I used the the original wire loom and did NO splicing. I used the existing pig tail and attached it directly to the back of the gauge (perfect fit). The exisiting wires ends are female and the gauge connections are male. The only splicing I did was to remove the dash lights (blue with red stripe wire) and hooked up the lights using these wires.

Check out wiring:

geostang351 · Apr 6, 2007

I measured the resistance at the sender with power on and it was reading 85 ohms of resistance. SOes this really mean that me float and sensor in the tank is no longer good? I can't believe it stopped working correctly as I made this upgrade. But, I guess that's the nature of the hobby.

reenmachine · Apr 6, 2007

I see the voltage regulator mounted to the back of your tach. Is this an old pic? I believe you said that you were running the gauges off of straight 12V, which would be correct. You don't want the CVR anymore.

The resistance gets higher as the fuel level decreases, so it would seem that either you're totally empty (I think you said you're totally full) or may have a bad sending unit.

Can someone else chime in about sending unit testing? It's been a while since I've messed with a stock one. Also try doing a forum search about this.

DJCarbine · Apr 6, 2007

A week before I got my autometer gauges installed, the fuel sending unit took a crap. Sometimes thats just how it work out

geostang351 · Apr 7, 2007

reenmachine said:
I see the voltage regulator mounted to the back of your tach. Is this an old pic? I believe you said that you were running the gauges off of straight 12V, which would be correct. You don't want the CVR anymore.

You are correct in that you see the CVR, but it is only there so that I don't lose it. It's not hooked up to anything.

reenmachine said:
The resistance gets higher as the fuel level decreases, so it would seem that either you're totally empty (I think you said you're totally full) or may have a bad sending unit..

Yes, I do have a full tank. I just find it hard to believe that the sending unit just went bad as I did this. I still have the stock fuel gauge and CVR. MAybe I should hook it back up and see what happens.

geostang351 · Apr 20, 2007

Ok, put the senders in that came along with the gauges. Oil pressure gauge works great shown at about 60 PSI. Still having no sign with the fuel gauge. I think a new sender is on the agenda.

Water temp - The needle barely moved. My problem (I think) is this; the sending unit that came with the gauge was too small for my intake. I went to Autozone and bought a fitting that would accept the sender AND screw into the intake, but the sender does not protrude into the intake and the bottom of the sender sits flush with the fitting I bought. Does the sender need to sit further down into the antifreeze to get a better temp reading?

reenmachine · Apr 20, 2007

You got it -- that puppy's got to be down in the water to read right. Usually the gauge comes with an assortment of adapters and they are shorter for this reason.

geostang351 · Apr 21, 2007

reenmachine said:
You got it -- that puppy's got to be down in the water to read right. Usually the gauge comes with an assortment of adapters and they are shorter for this reason.

They did come with an assortment of fittings but of course, none of them fit my edelbrock dual plane intake. Back to "The Zone".

Thanks REEN!!!

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