What are these parts on my firewall? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Thundarr · 05-16-2019, 12:55 PM

71 GMC Sierra Grande with a mid 80's SBC 350.
Can you tell me what these electrical parts are on my firewall?

I've unplugged them and don't see anything else not working but my tach has never worked. At least one of these parts (relay/voltage regulator/ac generator/unknown) looks pretty old.

Thanks guys.

Bearhawg · 05-16-2019, 02:39 PM

The one on the left looks very much like the relay that was connected to the transmission spark advance on my '70 It had been disconnected from the trans for years. I finally took it off the firewall when I replaced the engine harness.

rcazwillis · 05-17-2019, 04:26 PM

Both are spark control items. Many people remove them and the associated wiring. Won't affect anything. Look over the wiring diagrams on the forum to see what can be removed.

**rechinca** · 05-17-2019, 08:06 PM

Yep, TSC THINGS THAT ARE NOT NEEDED. If you want you can also remove the sensor in the passenger side head. But drain the block first or you will be wearing coolant and swearing.

**Steeveedee** · 05-17-2019, 10:18 PM

Quote:

Originally Posted by rechinca

Yep, TSC THINGS THAT ARE NOT NEEDED. If you want you can also remove the sensor in the passenger side head. But drain the block first or you will be wearing coolant and swearing.

I thought that the Transmission Controlled Spark Thermal Vacuum Switch was in the manifold just behind the thermostat housing, or in some cases, in the thermostat housing, and the temperature sensor for the gauge was in the passenger side head?

**rechinca** · 05-18-2019, 07:40 AM

The TSC sensor is in the passenger side head and the factory temp gauge sender is in the drivers side head. There was some part of the TSC system in the manifold, but the coolant sensor it hooked to was in the head under the exhaust manifold.

**71CHEVYSHORTBED402** · 05-18-2019, 01:15 PM

TCS Relay and TCS Delay.

Thundarr · 05-18-2019, 04:22 PM

Thanks guys. I'll take those off.

Any ideas on my battery voltage gauge not working. Are there some typical parts to replace or places to start?

**rechinca** · 05-18-2019, 06:19 PM

The factory battery gauge is an Ammeter gauge not a Voltage gauge. It reads charge/discharge arrangement so you will not see a reading like a volt style one reads. There is a member in Oregon who sells a conversion kit to make it into a volt reader.

**Steeveedee** · 05-18-2019, 10:17 PM

Look at your harness for the fuses for the charging system. It only takes one to be blown for the gauge to not indicate charge//discharge.

Thundarr · 05-22-2019, 11:13 AM

Steeveedee,
Are you referring to "inline" fuses along the wiring harness in the engine bay?
Not on the fuse block?

I replaced a few that I found years ago that were blown but I need to go see if I can find any others.

**Stocker** · 05-22-2019, 05:34 PM

This is what you're looking for. There are two in the engine compartment near the front of the truck-- one on the right side near the battery, and one on the left side.

stsalvage · 05-22-2019, 07:16 PM

battery voltage gauge on all cars and trucks Leave them alone or disconnect them. seen more cars and trucks catch fire due to the Voltage gauge. There a fire just waiting to happen. Trust me If you're having a voltage problem you don't need a gauge to tell you your wipers will be slow your lights will be dim your starter will drag. If your not into car's or trucks by the time you get into these old trucks Best off stay with New car's and trucks.

In my 1960 and my 1966 bobtails, I drove while hauling trusses for new housing back in the 80's here in Calif My boss unplugged the voltage gauge wires to are gauges. I found out when I got my own 1965 3/4ton. Rules of driving these trucks Never drive an old truck with old wires connected to the Voltage gauge. If you like your classic car or truck I forewarn you Unplug or tape up the wires you don't need them.

stsalvage · 05-22-2019, 07:18 PM

Quote:

Originally Posted by Stocker

This is what you're looking for. There are two in the engine compartment near the front of the truck-- one on the right side near the battery, and one on the left side.

The fuse is for the side blinker for the 1971-72 chevy trucks It's not for the voltage gauge

stsalvage · 05-22-2019, 07:19 PM

I'm hoping to install something like this on the Rear side markers that don't blink while you making a right or left hand turn

**Stocker** · 05-22-2019, 08:02 PM

Quote:

Originally Posted by stsalvage

The fuse is for the side blinker for the 1971-72 chevy trucks It's not for the voltage gauge

My K20 has an ammeter, not a voltage gauge.... and it has the two 4A fuses for the ammeter. If either fuse fails, the ammeter won't work.

Reference this thread for more info & clarification, in particular post #2 and post #4 by VetteVet. http://67-72chevytrucks.com/vboard/s...d.php?t=714782

**Jiggers72-GMC** · 10-23-2021, 08:46 AM

Old thread, yes I know, great info right here, love this forum and all the great members.

05-16-2019, 12:55 PM	#1
Thundarr Registered User Join Date: May 2013 Location: Coppell, Texas Posts: 176	What are these parts on my firewall? 71 GMC Sierra Grande with a mid 80's SBC 350. Can you tell me what these electrical parts are on my firewall? I've unplugged them and don't see anything else not working but my tach has never worked. At least one of these parts (relay/voltage regulator/ac generator/unknown) looks pretty old. Thanks guys. Attached Images __________________ 1971 GMC C15 Sierra Grande SWB 1972 Chevy C10 Custom Deluxe LWB 2018 GMC Yukon Denali

05-17-2019, 04:26 PM	#3
rcazwillis Registered User Join Date: Aug 2013 Location: Fort Worth, TX Posts: 309	Re: What are these parts on my firewall? Both are spark control items. Many people remove them and the associated wiring. Won't affect anything. Look over the wiring diagrams on the forum to see what can be removed. __________________ Zane's 71 Build

05-18-2019, 07:40 AM	#6
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 535	Re: What are these parts on my firewall? The TSC sensor is in the passenger side head and the factory temp gauge sender is in the drivers side head. There was some part of the TSC system in the manifold, but the coolant sensor it hooked to was in the head under the exhaust manifold. __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

05-18-2019, 01:15 PM	#7
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,385	Re: What are these parts on my firewall? TCS Relay and TCS Delay. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly guide (kit) for restoring this truck from the ground up, complete with details including full hardware descriptions. Much of the info. applies to all 67-72 GM. My build thread, with some info. about the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025

05-18-2019, 04:22 PM	#8
Thundarr Registered User Join Date: May 2013 Location: Coppell, Texas Posts: 176	Re: What are these parts on my firewall? Thanks guys. I'll take those off. Any ideas on my battery voltage gauge not working. Are there some typical parts to replace or places to start? __________________ 1971 GMC C15 Sierra Grande SWB 1972 Chevy C10 Custom Deluxe LWB 2018 GMC Yukon Denali

05-16-2019, 02:39 PM	#2
Bearhawg Registered User Join Date: Feb 2018 Location: Snellville GA Posts: 104	Re: What are these parts on my firewall? The one on the left looks very much like the relay that was connected to the transmission spark advance on my '70 It had been disconnected from the trans for years. I finally took it off the firewall when I replaced the engine harness.

05-17-2019, 08:06 PM	#4
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 535	Re: What are these parts on my firewall? Yep, TSC THINGS THAT ARE NOT NEEDED. If you want you can also remove the sensor in the passenger side head. But drain the block first or you will be wearing coolant and swearing. __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

05-18-2019, 06:19 PM	#9
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 535	Re: What are these parts on my firewall? The factory battery gauge is an Ammeter gauge not a Voltage gauge. It reads charge/discharge arrangement so you will not see a reading like a volt style one reads. There is a member in Oregon who sells a conversion kit to make it into a volt reader. __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

05-18-2019, 10:17 PM	#10
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,928	Re: What are these parts on my firewall? Look at your harness for the fuses for the charging system. It only takes one to be blown for the gauge to not indicate charge//discharge. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

05-22-2019, 11:13 AM	#11
Thundarr Registered User Join Date: May 2013 Location: Coppell, Texas Posts: 176	Re: What are these parts on my firewall? Steeveedee, Are you referring to "inline" fuses along the wiring harness in the engine bay? Not on the fuse block? I replaced a few that I found years ago that were blown but I need to go see if I can find any others. __________________ 1971 GMC C15 Sierra Grande SWB 1972 Chevy C10 Custom Deluxe LWB 2018 GMC Yukon Denali

05-22-2019, 05:34 PM	#12
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,806	Re: What are these parts on my firewall? This is what you're looking for. There are two in the engine compartment near the front of the truck-- one on the right side near the battery, and one on the left side. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

05-22-2019, 07:16 PM	#13
stsalvage Scrapper 1 Join Date: Jan 2007 Location: Riverside Calif Posts: 1,649	Re: What are these parts on my firewall? battery voltage gauge on all cars and trucks Leave them alone or disconnect them. seen more cars and trucks catch fire due to the Voltage gauge. There a fire just waiting to happen. Trust me If you're having a voltage problem you don't need a gauge to tell you your wipers will be slow your lights will be dim your starter will drag. If your not into car's or trucks by the time you get into these old trucks Best off stay with New car's and trucks. In my 1960 and my 1966 bobtails, I drove while hauling trusses for new housing back in the 80's here in Calif My boss unplugged the voltage gauge wires to are gauges. I found out when I got my own 1965 3/4ton. Rules of driving these trucks Never drive an old truck with old wires connected to the Voltage gauge. If you like your classic car or truck I forewarn you Unplug or tape up the wires you don't need them.

05-22-2019, 07:19 PM	#15
stsalvage Scrapper 1 Join Date: Jan 2007 Location: Riverside Calif Posts: 1,649	Re: What are these parts on my firewall? I'm hoping to install something like this on the Rear side markers that don't blink while you making a right or left hand turn

10-23-2021, 08:46 AM	#17
Jiggers72-GMC Senior Member Join Date: Mar 2021 Location: up North Posts: 550	Re: What are these parts on my firewall? Old thread, yes I know, great info right here, love this forum and all the great members. __________________ Gerry, North Bay Ontario 1971 Chevy K10 short stepper, 518 med green & white 1972 GMC C1500 long box, dark Brown, owned since 1977 1969 GMC C2500 manual



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