[DeTomaso] Pantera Tach Shows 0 at Cold Idle
dennis617 at aol.com
dennis617 at aol.com
Wed Dec 30 09:44:47 EST 2020
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)
* Example of revving the motor when cold
([2]https://youtu.be/kWaRfGfj2HU)
* Warm running and every thing works fine
([3]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. https://youtu.be/yIFtsp0ljzk
2. https://youtu.be/kWaRfGfj2HU
3. https://youtu.be/X1RY4VwmSmA
_______________________________________________
Detomaso Email List is not managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
DeTomaso at server.detomasolist.com
http://server.detomasolist.com/mailman/listinfo/detomaso
To manage your subscription (change email address, unsubscribe, etc.) use the links above.
Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages.
-------------- next part --------------
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][1]https://youtu.be/yIFtsp0ljzk)
* Example of revving the motor when cold
([2][2]https://youtu.be/kWaRfGfj2HU)
* Warm running and every thing works fine
([3][3]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. [4]https://youtu.be/yIFtsp0ljzk
2. [5]https://youtu.be/kWaRfGfj2HU
3. [6]https://youtu.be/X1RY4VwmSmA
_______________________________________________
Detomaso Email List is not managed by POCA
Posted emails must not exceed 1.5 Megabytes
DeTomaso mailing list
[7]DeTomaso at server.detomasolist.com
[8]http://server.detomasolist.com/mailman/listinfo/detomaso
To manage your subscription (change email address, unsubscribe, etc.)
use the links above.
Members who post to this list grant license to the list to forward any
message posted here to all past, current, or future members of the
list. They also grant the list owner permission to maintain an archive
or approve the archiving of list messages.
References
1. https://youtu.be/yIFtsp0ljzk
2. https://youtu.be/kWaRfGfj2HU
3. https://youtu.be/X1RY4VwmSmA
4. https://youtu.be/yIFtsp0ljzk
5. https://youtu.be/kWaRfGfj2HU
6. https://youtu.be/X1RY4VwmSmA
7. mailto:DeTomaso at server.detomasolist.com
8. http://server.detomasolist.com/mailman/listinfo/detomaso
More information about the DeTomaso
mailing list