troubleshooting rally pack sending units
February 26th, 2017, 04:56 PM
#1
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troubleshooting rally pack sending units
Looking for some help troubleshooting a rally pack sending unit, or maybe its the wiring... anyway:
Working on a 68 442, 455 swap.
Motor came with idiot lights, car came with rally pack.
Sending units are new:
-Temp is Lectric Limited from Fusick and correct for a gauges according to the part number on the box. Has the correct blade as opposed to button terminal.
-Oil is from Fusick.
Harnesses are new from Lectric as well
Refurbished the gauges myself (except for the clock in the tach) using small screws to hold the pins firmly to the printed circuits.
Starting the car after installing everything (next to northing worked before) and everything works but the temp gauge. The needle sits in the mid range of the gauge, pegs to "C" when the key is turned and stays there after cranking. Car warms up to about 200 according to aftermarket gauges but the needle stays pegged. I used teflon tape in the installation, but I get almost 0 ohms between the case of the sensor and the manifold. Any ideas?
Oil seems fine, reads at the center line while after market gauges read about 40 psi, but jumps around a lot. Seem normal?
Working on a 68 442, 455 swap.
Motor came with idiot lights, car came with rally pack.
Sending units are new:
-Temp is Lectric Limited from Fusick and correct for a gauges according to the part number on the box. Has the correct blade as opposed to button terminal.
-Oil is from Fusick.
Harnesses are new from Lectric as well
Refurbished the gauges myself (except for the clock in the tach) using small screws to hold the pins firmly to the printed circuits.
Starting the car after installing everything (next to northing worked before) and everything works but the temp gauge. The needle sits in the mid range of the gauge, pegs to "C" when the key is turned and stays there after cranking. Car warms up to about 200 according to aftermarket gauges but the needle stays pegged. I used teflon tape in the installation, but I get almost 0 ohms between the case of the sensor and the manifold. Any ideas?
Oil seems fine, reads at the center line while after market gauges read about 40 psi, but jumps around a lot. Seem normal?
February 26th, 2017, 05:48 PM
#2
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Location: Poteau, Ok
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Take the sensor back out and remove the tape. Then with the key on ground the wire, the gauge should go to hot, open the circuit, it should to C. The tape is probably keeping the circuit open.
February 27th, 2017, 08:51 AM
#3
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Did not have a chance to take the tape off the sender this morning, but ran the grounding test and something does not seem right:
With key on and circuit open, needle pegs to Cold
With key on and temp sender wire grounded to negative battery terminal, needle rises to just over the gauge's 1/2 way mark
Any insight?
With key on and circuit open, needle pegs to Cold
With key on and temp sender wire grounded to negative battery terminal, needle rises to just over the gauge's 1/2 way mark
Any insight?
February 27th, 2017, 10:16 AM
#5
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But why do you reckon the grounded circuit only makes the gauge read at the 1/2 way mark?
I assume its like the fuel gauge and reads resistance to ground... but...
Busted gauge? bad resistor? wrong resistor?
February 27th, 2017, 10:40 AM
#7
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Also on the pegging on start from another post:
There should be a green wire in the harness that comes down inside the steering column from the turn signal/ignition assembly. There is usually a bracket where the harness emerges from the steering column, just under the dash, and the plastic harness end is hung on that bracket. If you simply disconnect the green wire from the harness and tape it off, that should solve the pegging problem. All of my GM cars have run from the '68 model year to the '72 model year and that's what I did in every case (for '68 it was the green wire from the backside of the ignition on the dash) when I converted from idiot lights to gauges.
You should be able to back the green wire out of the plastic harness without cutting it. There is a metal tab that holds the wire in the harness that you should be able to see if you shine a light into it. With a very small screwdriver, you should be able to push down the tab and back the wire out of the harness.
I've heard a couple of theories on if the pegging is harmful or not to the gauge. One theory was that, with continued pegging, it will eventually damage the gauge. The other theory I've heard is that the pegging won't have any ill effects on the gauge at all.
A car that came from the factory with gauges didn't have the pegging problem. I personally like to keep it that way so that's why I disconnected the green wire in the conversions I did.
Randy C.
You should be able to back the green wire out of the plastic harness without cutting it. There is a metal tab that holds the wire in the harness that you should be able to see if you shine a light into it. With a very small screwdriver, you should be able to push down the tab and back the wire out of the harness.
I've heard a couple of theories on if the pegging is harmful or not to the gauge. One theory was that, with continued pegging, it will eventually damage the gauge. The other theory I've heard is that the pegging won't have any ill effects on the gauge at all.
A car that came from the factory with gauges didn't have the pegging problem. I personally like to keep it that way so that's why I disconnected the green wire in the conversions I did.
Randy C.
February 27th, 2017, 01:22 PM
#8
Randy C.
Join Date: Feb 2009
Location: Albany, OR
Posts: 3,245
My post about stopping the pegging is ALMOST right...I had to change it in follow-up posts for that particular instance. It 's not the harness that comes down the steering column - that harness handles the turn signals and such. The harness where the green wire needs to be extracted and taped off is the harness that plugs into the switch on top of the steering column under the dash. It's a bit hard to get to but it can be done. I did it on my '68 4-4-2 and '70 GTO when converting from idiot lights to factory gauges and it solved the pegging problem.
The only thing I don't understand is that you said the car came with factory gauges. If it did, the check circuit with the green wire shouldn't be there. If it is there, is it possible someone before you swapped out the idiot lights for gauges? If so, then the green wire will be there.
The sending units for both the engine temp and oil pressure definitely need to be changed to accommodate gauges. The gauges won't work properly with idiot light sending units.
Ditto on removing the teflon tape!
Randy C.
The only thing I don't understand is that you said the car came with factory gauges. If it did, the check circuit with the green wire shouldn't be there. If it is there, is it possible someone before you swapped out the idiot lights for gauges? If so, then the green wire will be there.
The sending units for both the engine temp and oil pressure definitely need to be changed to accommodate gauges. The gauges won't work properly with idiot light sending units.
Ditto on removing the teflon tape!
Randy C.
February 27th, 2017, 02:40 PM
#9
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Join Date: Sep 2014
Location: Central Mass
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My post about stopping the pegging is ALMOST right...I had to change it in follow-up posts for that particular instance. It 's not the harness that comes down the steering column - that harness handles the turn signals and such. The harness where the green wire needs to be extracted and taped off is the harness that plugs into the switch on top of the steering column under the dash. It's a bit hard to get to but it can be done. I did it on my '68 4-4-2 and '70 GTO when converting from idiot lights to factory gauges and it solved the pegging problem.
The only thing I don't understand is that you said the car came with factory gauges. If it did, the check circuit with the green wire shouldn't be there. If it is there, is it possible someone before you swapped out the idiot lights for gauges? If so, then the green wire will be there.
The sending units for both the engine temp and oil pressure definitely need to be changed to accommodate gauges. The gauges won't work properly with idiot light sending units.
Ditto on removing the teflon tape!
Randy C.
The only thing I don't understand is that you said the car came with factory gauges. If it did, the check circuit with the green wire shouldn't be there. If it is there, is it possible someone before you swapped out the idiot lights for gauges? If so, then the green wire will be there.
The sending units for both the engine temp and oil pressure definitely need to be changed to accommodate gauges. The gauges won't work properly with idiot light sending units.
Ditto on removing the teflon tape!
Randy C.
I'll look into it, the Dash harness is new from American Autowire, but matched my original (minus the splices and duct tape). Sending units are repros for gauged applications.
I'll ditch the teflon tape and see what happens... does this mean I should take the teflon tape off of the oil sending unit as well?
Randy, I think it was your thread I referenced when I repaired my circuit boards. Does it sound right that my gauge only reads about half when the circuit is grounded? Any idea what the resistance value (ohms) of the temp gauge resistor should be?
February 27th, 2017, 07:48 PM
#10
Randy C.
Join Date: Feb 2009
Location: Albany, OR
Posts: 3,245
I don't know what those readings should be, but it doesn't sound right to me. I'm thinking it should be all the way to the bottom. When I did my wiring for gauges for the '68 4-4-2 (came with idiot lights), '69 4-4-2 (came with gauges), and '70 GTO (came with idiot lights), everything worked as it should after I got done. Maybe I just got lucky!
Randy C.
Randy C.
March 14th, 2017, 08:28 AM
#11
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Location: Central Mass
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update
So I took the gauge back out, I was wrong, readings on the gauge resistors were all close to 90 ohms. Had some oxidized contacts, so used a dremel tool with a wire brush and some steel wool to get ell my contacts nice and shiny. Grounding the gauge moves the needle a little higher, but still only a little over half way. I had hoped to start the car and try things with the motor running, but now the car won't start, hoping its just fouled plugs from all the idling i've been doing as I test out all this new wiring, but lookout for my next thread!
Anyway, back to the gauges, I called John at Redline Gauge Repair who repaired my tic-toc tach (great guy, great work, highly recommend him, give him your business, here's his website: http://www.redlineg.com/redlineg/Welcome.html), and he gave me some free advice, but none of it helped. Seems like its probably in the gauge, which is above my skill/knowledge level.
Anyway, John charges $55.00 per gauge to repair but always sees what is needed and confirms a quote. He'll also calibrate gauges to their sending units (you have to send them with the gauge obviously) for $10.00 per gauge. With all that he'll bead blast the can, clean everything unto make sure the illumination is on point, and acid etch the circuit board to clean up any oxidization. So I'm looking at about $75.00 for repairs/calibrations plus shipping and insurance for a gauge that should be good as new. Feels pretty reasonable and I was very satisfied with my tach/clock.
Hope this doesn't read like an ad for Redline/John, but I like to spread the word, if not for another thread on CO, I wouldn't have found him.
Anyway, back to the gauges, I called John at Redline Gauge Repair who repaired my tic-toc tach (great guy, great work, highly recommend him, give him your business, here's his website: http://www.redlineg.com/redlineg/Welcome.html), and he gave me some free advice, but none of it helped. Seems like its probably in the gauge, which is above my skill/knowledge level.
Anyway, John charges $55.00 per gauge to repair but always sees what is needed and confirms a quote. He'll also calibrate gauges to their sending units (you have to send them with the gauge obviously) for $10.00 per gauge. With all that he'll bead blast the can, clean everything unto make sure the illumination is on point, and acid etch the circuit board to clean up any oxidization. So I'm looking at about $75.00 for repairs/calibrations plus shipping and insurance for a gauge that should be good as new. Feels pretty reasonable and I was very satisfied with my tach/clock.
Hope this doesn't read like an ad for Redline/John, but I like to spread the word, if not for another thread on CO, I wouldn't have found him.
March 15th, 2017, 03:40 PM
#12
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Join Date: Aug 2010
Posts: 771
Not an expert here, but just looked at my 70 with gauges .Are you sure you have the correct sender?
The sender on my 70 is the **** style connector not the spade.
Just a thought, don't know if the connector on the sender is indicative of the use??
The sender on my 70 is the **** style connector not the spade.
Just a thought, don't know if the connector on the sender is indicative of the use??
March 15th, 2017, 05:36 PM
#13
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But you would think that based on what the gauge does that it would read something. I still wonder if they sent me the wrong one... the part numbers check out. Who knows though, its just a number on a box, it could still be the wrong one!
I'll get the gauge fixed and then make sure the sending unit is correct
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