Re 1970 XR7 convertible. While replacing the speedometer cable, I thought it would be good chance to replace the broken cluster connector, printed circuit board, and replace the instrument bulbs with LED lights. All parts came from WCCC. Now I can’t get any cluster lights to work except the right turn signal indicator. I was very careful when replacing the white connector with one lead at a time. Polarity of the LED lights was carefully followed from HiPo’s instructions. With ignition switch on, the temp gauge will go to max. So I replaced the instrument voltage regulator with a new solid state unit, but got the same result. Sounds like a ground fault, but all checks appear to be good. Kinda acts like some of the connector pins aren’t making good contact with the new circuit board. Any ideas what to check next? Maybe Richard Gunn can help me out.
The solid state IVR’s are a nightmare since they take 30 seconds to turn on - so you don’t have any oil pressure indication during startup. Not worth much in my estimation. The originals work well.
thanks Royce, good to know. I’ll put my old one back in and hope it still works.
Some progress. Got the illumination LEDs working and both turn signals, but temp and oil pressure gauges still not working. Temp gauge goes to max. The old mechanical IVR appears dead when tested with the Ford gauge tester (no voltage). The solid state IVR does show constant voltage, but temp gauge still goes to max. Looks like I’ll be ordering an NOS IVR, and hope the gauge isn’t fried. I still think some of the brass pins on the harness connector are not making proper contact with the circuit board, or perhaps not in the correct position. Can anyone tell me the correct wire colors for the harness connector by pin number? I have the classiccarwiring.com sheet but it doesn’t appear to be 100% correct according to my original harness connector.
Your fuel gauge maxing out may be due to a short somewhere between the gauge and the sending unit.
Here’s the pin-out for a 70 XR7.
| Dash Cluster pin 1 | green/black | 34 | high beam |
|---|---|---|---|
| Dash Cluster pin 2 | white/blue | 49 | RH turn signal |
| Dash Cluster pin 4 | green/white | 50 | LH turn signal |
| Dash Cluster pin 5 | red | 655 | ammeter |
| Dash Cluster pin 6 | yellow | 654 | ammeter |
| Dash Cluster pin 7 | yellow/black | 215 | low fuel signal |
| Dash Cluster pin 8 | green/red | 162 | parking brake signal |
| Dash Cluster Pin 9 | yellow/white | 29 | fuel sending unit |
| Dash Cluster pin 10 | red/yellow | 640 | coil run signal |
| Dash Cluster pin 11 | violet | 520 | seat belt signal |
| Dash Cluster pin 12 | black Violet |
484 30 |
CVR input power |
| Dash Cluster Pin 13 | red/white | 39 | temperature sending unit |
| Dash Cluster pin 14 | black/violet | 127 | door ajar signal |
| Dash Cluster pin 15 | white/red | 31 | oil pressure sending unit |
| Dash Cluster pin 16 | purple | 977 | dual brake warning switch |
| Dash Cluster pin 17 | blue/red | 19C | dash lights |
| Dash Cluster pin 18 | black | 57 | Ground |
Thanks a million. I’ll compare this to my harness connector and let you know what I find.
The temperature gauge is maxing out. The fuel gauge hasn’t worked for some time (I need to pull the sending unit out and replace the float).
Your temp gauge is maxing out? Same idea as fuel: a short in the wire somewhere. You can remove the sending unit connector and see if it is the sending unit itself that’s bad (unlikely) or isolate the short by pulling the engine gauge feed plug at the firewall. If the problem goes away, the problem is in that harness.
Something to look in to. Did the cluster get taken apart? If so it is possible the gauges are shorting to the case. You need to check the alignment and look for the insulating pads. If it was not then never mind. Good luck getting it sorted out.
Wiring to harness connector checks out, except pin 10 has two red/yellow leads, and pin 11 is violet with white tracer. A voltage check with key on, has 12 vdc on pins 5, 6, 10, and 12 which looks correct. Pins 1, 2, 4, 7, 14, 17 and 18 have continuity to ground. I’ll have to wait till the new NOS IVR arrives to do further testing.
Cluster has not been taken apart. Not yet at least. Once the NOS IVR arrives, I’ll recheck the gauges. If any of them are toast I’ll have to take everything apart, replace damaged gauges and pay attention to the insulator pads and alignment as you point out. Thanks
BlockquoteWiring to harness connector checks out, except pin 10 has two red/yellow leads, and pin 11 is violet with white tracer. A voltage check with key on, has 12 vdc on pins 5, 6, 10, and 12 which looks correct. Pins 1, 2, 4, 7, 14, 17 and 18 have continuity to ground. I’ll have to wait till the new NOS IVR arrives to do further testing.
Pin 10 is fine, as is pin 11 (violet with white tracer).
Pins 1,2,4, 7,14 and 17 may show continuity to ground because there’s a lamp in the circuit, and it only has about 1 ohm of resistance.
Pins 5, 6, 10, and 12 should show 12V; the first 2 at all times, pin 10 when the key is in RUN, and Pin 12 when in ACC or RUN.
I don’t see any problem with your readings.
Still no luck. Measurements were taken on the harness connector pins with the instrument cluster out, so no bulbs involved. My original IVR tested good on the bench, but pulsing at only 3-4 volts, so I adjusted it up to 5v, but when installed, no voltage reading on the temperature sensor lead, and temp gauge goes to max. I have a new electro-mechanical IVR with same result. Interesting to note that the electro-mechanical IVRs will put out 10-12v for a few seconds before settling down to the 5 volt pulse. The solid state IVR when bench tested started the 5v pulse immediately with no delay, so I guess it might depend on who makes them. But same result with either type. Instrument cluster was working fine when I started the speedometer cable change, so I think the problem has to be the repro circuit board and repro harness connector causing problems. When the cluster is removed, I can see witness marks on the circuit board connector tabs so they must be making proper contact. I don’t know what to try next. What started out as a simple project has turned into a real nightmare!
Badcatt: yes I rechecked the gauge alignment and insulator pads. All gauges were in their proper notches and insulators were good. Continuity testing on all gauge pins confirm no shorts to the cluster.
Further testing reveals infinite resistance on the temperature sending unit, so it looks like I need to replace that. I bench tested all the LED lights in the cluster and they all work fine. I also tested the resistance across the temp, oil pressure and fuel gauges, and got around 13-14 ohms which seems about right to me. However, when rechecking checking continuity and resistance on the cluster printed circuit between each of the gauge’s 5v feed point and common cluster ground, I’m getting 13-14 ohms. This doesn’t seem right to me. Wouldn’t this be essentially grounding the 5v to each gauge (temp goes to max when key is in the ACC or run position)? When cluster is plugged into the harness connector, I’m not usually getting voltage to the temperature sending wire.
How are you measuring the output voltage of the IVR?
With cluster on the workbench, I feed 12v to the IVR’s input, and using common ground, I get 5vdc on the IVR’s output. Same result with either solid state IVR or electromechanical unit (pulsing 5v).
Are you using a multi meter? You should get a constant 5 volts from a solid state IVR but the original puts out pulses of 12 volts. Only a few very expensive meters will do the long term averaging to show that the pulses average to 5 volts over time.
What you can do to bench test is to first use two 1.5 volt batteries in series to create a 3 volt source. Put positive to one leg of the gauge and negative to the other. Polarity is not important. This should after about 20 seconds drive the gauge to full or hot reading. If not the gauge is out of spec. Once you have verified that the gauge is correct you can then adjust the mechanical style IVR. You will need either a gauge tester or a 5 watt 10 ohm resistor to substitute for the sender. On the bench that means you ground one end of the resistor and the case of the IVR, Then run 12 volts to the input of the IVR and the IVR output to the gauge.
If your gauge is off then you can send it to Rocketman who will recalibrate it for just $15.
It isn’t right. What is happening is that one of your gauge’s output pin is grounded to the case, and since all the gauges are tied together via the IVR output line, all gauges will show 14 ohms between input side of the gauge (IVR output) and ground. This is a lucky situation, as now you can measure the other gauge’s output posts to find which one has grounded (0-1 ohm). A gauge that is not grounded should show kilo-ohms. Find the bad gauge and re-set it in the dash cluster housing.
Thanks Randy. I’ll have to take the cluster apart and let you know what I find. I need to replace the temperature sender regardless.
Well the good news is that the temp, oil pressure, and fuel gauges are all working fine on the bench test, and pretty much spot on when tested with the Ford gauge tester. Yippie! Still looking for the ground fault. All the insulators look good though.