[DeTomaso] Pantera Tach Shows 0 at Cold Idle
Mike Reilly
reillyms at live.com
Wed Dec 30 11:58:37 EST 2020
Hi all. Thanks for the input. I suspect a ground issue somewhere in the circuit which I’ll try to run down. Although I did try giving the tach it’s own ground wire but that didn’t change the behavior. I did install a new fuse box and ignition switch controller (ISC) from Jon Haas so I may have caused some grounding issue as I moved wires around. I did trouble shoot with Jon months ago but all his products seemed to be working as designed. It was doing this before I switch to the new fuse box. I was hoping the new fuse box would help. It hadn’t done it before the ISC was installed but I also had a no start issue then due to a bad ignition switch. So I was touching lots of wiring then.
I’ll have some detective work to do here and may need to trace the circuit and check everything as folks have suggested. I’ll probably reach out to Jon for any further suggestions as well. Fun with decades old wiring : )
Dennis, I have a DuraSpark distributor and electronic ignition system that’s been in the car since 1992 and it didn’t require a tach adaptor. I only recently had this problem come up so I don’t think it’s my ignition system : (
Thanks, Mike
From: dennis617 at aol.com<mailto:dennis617 at aol.com>
Sent: Wednesday, December 30, 2020 6:44 AM
To: reillyms at live.com<mailto:reillyms at live.com>; detomaso at server.detomasolist.com<mailto:detomaso at server.detomasolist.com>
Subject: RE: [DeTomaso] Pantera Tach Shows 0 at Cold Idle
Hi Mike,
I've been having a similar problem with my tach, although, I've never tried the the window switch trick. When my car sits idle for a long period I find that my tach stops working until I drive it for a few minutes or if it gets a chance to really warm up. I haven't solved the problem yet, but I suspect that it is the tach adapter that was installed when the engine was totally redone and I changed over to the FAST EZ 2.0 EFI and a mallory ignition system. I never had any problems with my tach until the adapter was added to the system. Are you using an adapter as well?
Dennis
On Tuesday, December 29, 2020 Mike Reilly <reillyms at live.com> wrote:
Hi all. I've been having a weird tach problem for a few months now.
When I cold start the car the tach sits at zero but will respond when I
give it gas and go to 2000 RPMs for example. When I let off the gas it
goes back to zero yet the car is idling fine at around 900 RPMs. Now
when I push up on both window switches then the tach will respond and
read at idle speed but when I let go of the window switches the tach
goes back to zero. However, once the car is warmed up then the tach
works fine and shows idle speed etc. without ever going down to zero
unless the motor is turned off. If I restart the car when warm the
tack works fine. I think somehow I'm not getting enough voltage to the
tack when the car is cold.
Videos of the problem:
* Cold start and playing with the windows (you can hear me describing
what I'm doing near the end of this video)
([1]https://youtu.be/yIFtsp0ljzk<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FyIFtsp0ljzk&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925781170%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=oArOd%2BUyxza6sQUyDcErITtVE2O1k00C8T9oHGD0N6Y%3D&reserved=0>)
* Example of revving the motor when cold
([2]https://youtu.be/kWaRfGfj2HU<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FkWaRfGfj2HU&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925791167%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=z4RrWM5bC0Wphu7C9mk5Pu%2FtpeTEu7m%2BOBlsF%2BiT3Y4%3D&reserved=0>)
* Warm running and every thing works fine
([3]https://youtu.be/X1RY4VwmSmA<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FX1RY4VwmSmA&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925801158%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=vC6ux7G%2F%2F6JXPilQt1CrS5iMz2rQ9Y3kBC%2BHgruBy68%3D&reserved=0>)
Jon Haas rebuilt my tach as I thought that might have been the problem
but it was doing this behavior both before and after Jon's rebuild.
(By the way he does great work on rebuilds and found some cracked
resistors in my tach that were about to fail). I also converted to his
new alternator to replace my stock rebuilt alternator thinking that
would be the issue but the tach idle problem remained. This new
alternator has a built in voltage regulator.
I measured the various voltages coming to the tach and per my comms
with Jon these are correct voltages when the engine is running:
* Voltage at the tach (+terminal) light blue wire = 14.84V
* Voltage at the +coil wire = 14V
* Voltage at the +Duraspark = 14V
My Pantera is #7366 and is a 74L running a DuraSpark electronic
ignition. My battery is strong, new and kept on a trickle charger
Any ideas as to why when the motor is cold the tach won't register at
idle speed but does once the car is at operating temp? It's also
strange that it will come back to life when cold if I push up on both
window switches when the windows are already closed thus adding some
load to the car's electrical circuit.
Thanks, Mike Reilly
References
1. https://youtu.be/yIFtsp0ljzk<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FyIFtsp0ljzk&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925801158%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=QFW1uIu52STY3da9GrCDzITfmin7O4EzhgPRsfqnMJA%3D&reserved=0>
2. https://youtu.be/kWaRfGfj2HU<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FkWaRfGfj2HU&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925811157%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=C6cjno%2BMdL1SXeJ5%2Bc3Auxl9yz6acZ8oFl3Z46VHkmI%3D&reserved=0>
3. https://youtu.be/X1RY4VwmSmA<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FX1RY4VwmSmA&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925821152%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=djUHBWVGhOozhgSp7CQgd9RXm2Py94EbDzXNAY5mGVs%3D&reserved=0>
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Hi all. Thanks for the input. I suspect a ground issue somewhere in
the circuit which I'll try to run down. Although I did try giving the
tach it's own ground wire but that didn't change the behavior. I did
install a new fuse box and ignition switch controller (ISC) from Jon
Haas so I may have caused some grounding issue as I moved wires
around. I did trouble shoot with Jon months ago but all his products
seemed to be working as designed. It was doing this before I switch to
the new fuse box. I was hoping the new fuse box would help. It hadn't
done it before the ISC was installed but I also had a no start issue
then due to a bad ignition switch. So I was touching lots of wiring
then.
I'll have some detective work to do here and may need to trace the
circuit and check everything as folks have suggested. I'll probably
reach out to Jon for any further suggestions as well. Fun with decades
old wiring : )
Dennis, I have a DuraSpark distributor and electronic ignition system
that's been in the car since 1992 and it didn't require a tach
adaptor. I only recently had this problem come up so I don't think
it's my ignition system : (
Thanks, Mike
From: [1]dennis617 at aol.com
Sent: Wednesday, December 30, 2020 6:44 AM
To: [2]reillyms at live.com; [3]detomaso at server.detomasolist.com
Subject: RE: [DeTomaso] Pantera Tach Shows 0 at Cold Idle
Hi Mike,
I've been having a similar problem with my tach, although, I've never
tried the the window switch trick. When my car sits idle for a long
period I find that my tach stops working until I drive it for a few
minutes or if it gets a chance to really warm up. I haven't solved the
problem yet, but I suspect that it is the tach adapter that was
installed when the engine was totally redone and I changed over to the
FAST EZ 2.0 EFI and a mallory ignition system. I never had any
problems with my tach until the adapter was added to the system. Are
you using an adapter as well?
Dennis
[cid:image002.png at 01D6DE89.F5A25270]
On Tuesday, December 29, 2020 Mike Reilly <reillyms at live.com> wrote:
Hi all. I've been having a weird tach problem for a few months now.
When I cold start the car the tach sits at zero but will respond when
I
give it gas and go to 2000 RPMs for example. When I let off the gas
it
goes back to zero yet the car is idling fine at around 900 RPMs. Now
when I push up on both window switches then the tach will respond and
read at idle speed but when I let go of the window switches the tach
goes back to zero. However, once the car is warmed up then the tach
works fine and shows idle speed etc. without ever going down to zero
unless the motor is turned off. If I restart the car when warm the
tack works fine. I think somehow I'm not getting enough voltage to
the
tack when the car is cold.
Videos of the problem:
* Cold start and playing with the windows (you can hear me
describing
what I'm doing near the end of this video)
([1][4]https://youtu.be/yIFtsp0ljzk)
* Example of revving the motor when cold
([2][5]https://youtu.be/kWaRfGfj2HU)
* Warm running and every thing works fine
([3][6]https://youtu.be/X1RY4VwmSmA)
Jon Haas rebuilt my tach as I thought that might have been the
problem
but it was doing this behavior both before and after Jon's rebuild.
(By the way he does great work on rebuilds and found some cracked
resistors in my tach that were about to fail). I also converted to
his
new alternator to replace my stock rebuilt alternator thinking that
would be the issue but the tach idle problem remained. This new
alternator has a built in voltage regulator.
I measured the various voltages coming to the tach and per my comms
with Jon these are correct voltages when the engine is running:
* Voltage at the tach (+terminal) light blue wire = 14.84V
* Voltage at the +coil wire = 14V
* Voltage at the +Duraspark = 14V
My Pantera is #7366 and is a 74L running a DuraSpark electronic
ignition. My battery is strong, new and kept on a trickle charger
Any ideas as to why when the motor is cold the tach won't register at
idle speed but does once the car is at operating temp? It's also
strange that it will come back to life when cold if I push up on both
window switches when the windows are already closed thus adding some
load to the car's electrical circuit.
Thanks, Mike Reilly
References
1. [7]https://youtu.be/yIFtsp0ljzk
2. [8]https://youtu.be/kWaRfGfj2HU
3. [9]https://youtu.be/X1RY4VwmSmA
_______________________________________________
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[10]DeTomaso at server.detomasolist.com
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References
1. mailto:dennis617 at aol.com
2. mailto:reillyms at live.com
3. mailto:detomaso at server.detomasolist.com
4. https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FyIFtsp0ljzk&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925781170%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=oArOd%2BUyxza6sQUyDcErITtVE2O1k00C8T9oHGD0N6Y%3D&reserved=0
5. https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FkWaRfGfj2HU&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925791167%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=z4RrWM5bC0Wphu7C9mk5Pu%2FtpeTEu7m%2BOBlsF%2BiT3Y4%3D&reserved=0
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7. https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FyIFtsp0ljzk&data=04%7C01%7C%7Cf5ad5439d0804304ac2808d8acd176ac%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637449362925801158%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=QFW1uIu52STY3da9GrCDzITfmin7O4EzhgPRsfqnMJA%3D&reserved=0
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10. mailto:DeTomaso at server.detomasolist.com
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