Are the original Oil Pressure gauges mechanical - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ZEKE68 · 01-21-2018, 12:10 AM

I am wanting to add gauges to a warning light truck and wanted to use sending unit gauges for the oil pressure and water temp. Did all of the original gauge trucks have mechanical oil pressure gauges with the tubing running to the engine? From the pictures of the replacement gauge panels I have seen for sale they appear to have mechanical oil pressure and sending unit water temp gauges.

Rich69shortfleet · 01-21-2018, 12:11 AM

The oil pressure gauges are mechanical, requiring an oil pressure line off the engine to the gauge. The water temp is electrical using a sending unit. It is VERY important to use the correct sending unit or the readings on the temp gauge won't be accurate.

**LockDoc** · 01-21-2018, 12:23 AM

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Not sure if you have checked into it that far yet but you will also have to swap some wires around in the wiring connector so you don't fry your fuel gauge. There are a few threads on the procedure....

LockDoc

Rich69shortfleet · 01-21-2018, 01:04 AM

Quote:

Originally Posted by LockDoc

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Not sure if you have checked into it that far yet but you will also have to swap some wires around in the wiring connector so you don't fry your fuel gauge. There are a few threads on the procedure....

LockDoc

Or you can just swap in a gauges-specific underdash wiring harness which overall is the best bet for a drop-in plug and play deal.

**VetteVet** · 01-21-2018, 01:25 AM

Here's one.

http://67-72chevytrucks.com/vboard/s...d.php?t=588853

**VetteVet** · 01-21-2018, 01:37 AM

Here is a good thread on installing the battery gauge which has no wiring on a light gauge truck.

http://67-72chevytrucks.com/vboard/s...d.php?t=393139

**dmjlambert** · 01-21-2018, 01:48 AM

As far as the temp gauge part of the problem, the gauge cluster has both temp light and temp gauge. On gauge cluster trucks, the temp light is not wired and completely unused, but it's there and could be used. The sender for temp light and for temp gauge are different. Both are electric. The one for temp light is a switch, and the one for the gauge is variable resistance. Since you probably already have the sender for temp light, you could probably add the sender for temp gauge in the other head (got V-8?) and end up with both light and gauge working.

As LockDoc mentions, you can't just remove a warning light cluster and plug in a gauge cluster using the same plug, you would need to re-arrange the wiring in the plug, so proceed with caution.

You may also need to consider the generator warning light since the gauge cluster doesn't have one. I think the warning light may be necessary for proper voltage regulation, there are differences between the warning light trucks and gauge trucks that I don't understand when it comes to the alternator. The electrical questions forum is a good place to search and to ask for help.

To connect the battery gauge, it has 2 wires. Both should have a 4 amp fuse near the point where you connect them to the wiring harness. One connects to the 12 gauge red wire that comes off the battery at the fusible link, and the other one connects to the same 12 gauge red wire at the junction near the driver side headlight where it splits to separate wires going to the alternator and to the cab.

More info about the temperature senders:

Gauge:
It has been discussed before on other threads you can only use the stock 1/2" NPT threaded sender for the temp gauge if you have a stock instrument cluster. There is no 3/8" NPT sender that will work. If you have a 3/8" NPT threaded hole in the engine head, you can get a 1/2" sender and have a machinist turn and thread it to 3/8". I had forum member A1971Blazer turn and thread mine. Other people had it done by brian mac. I used GM part number 12334869, AC Delco number G1852.

Light:
If you change your engine and now have 3/8" instead of 1/2" NPT hole in the head and want to use the warning light, use Autozone Duralast or Wells part number TU78 for the sender.

These are threads on the subject that I have bookmarked and used:
http://67-72chevytrucks.com/vboard/s...d.php?t=490161
http://67-72chevytrucks.com/vboard/s...d.php?t=703388
http://67-72chevytrucks.com/vboard/s...d.php?t=627880
http://67-72chevytrucks.com/vboard/s...d.php?t=726025

Note: I see other have posted some good info for you while I was writing.

ZEKE68 · 01-21-2018, 11:18 AM

I had planned to change the dash wiring harness to a gauge type harness if I went to the gauge panel. Good info about the warning light in the gauge panel as I want to keep warning lights for the oil pressure and water temp even if I go to a gauge panel. Two options are 1 go with the new gauge panel and new harness and add warning lights for oil and water, or 2 keep the warning light panel and add oil and water gauges below the dash. If I do option 2 I can use sending unit gauges for oil and water. I am not a big fan of oil lines running into the interior as I have had copper lines break and plastic lines get melted by an electrical short before. Both were messy.

**dmjlambert** · 01-21-2018, 01:21 PM

You probably could get an electric type oil gauge and sender and modify the stock instrument cluster to house it, although I think with new copper tubing it may be unlikely for you to have a mess so I would probably go that route. Having a generator and oil pressure warning lights on the stock gauge instrument cluster may be something you can work in as well. I think you would have to be somewhat skilled at fabrication to make it look period correct. On the gauge instrument cluster the center is where the optional tachometer goes, and you could swap in the generator and oil light panel there, but that panel also has the turn signal indicators that may look out of place. So perhaps mask those. You can put a little tach or a clock between the generator and oil lights and that would look nice. I think an ideal cluster would have all those things. The other thing I have considered is make a blinking circuit out of some small microchips and relays that would use the temp light to mean overheat when solid on, generator or oil problem when blinking. Sort of use it as a check engine light. And another option is to buy an aftermarket instrument cluster that is the type where you just pick a bunch of gauges and lights and install them wherever you wish. Some of those look nice.

01-21-2018, 12:10 AM	#1
ZEKE68 Registered User Join Date: Jul 2012 Location: Space Coast, Florida Posts: 403	Are the original Oil Pressure gauges mechanical I am wanting to add gauges to a warning light truck and wanted to use sending unit gauges for the oil pressure and water temp. Did all of the original gauge trucks have mechanical oil pressure gauges with the tubing running to the engine? From the pictures of the replacement gauge panels I have seen for sale they appear to have mechanical oil pressure and sending unit water temp gauges. __________________ 1968 SWB Step Side, Big Block, 4L80E , Running!

01-21-2018, 12:11 AM	#2
Rich69shortfleet Registered User Join Date: May 2016 Location: Waverly, NE Posts: 334	Re: Are the original Oil Pressure gauges mechanical The oil pressure gauges are mechanical, requiring an oil pressure line off the engine to the gauge. The water temp is electrical using a sending unit. It is VERY important to use the correct sending unit or the readings on the temp gauge won't be accurate. __________________ 1965 Malibu SS L79 Restoration Page 1965 Two-Door Wagon Project Progress Page 2006 Pontiac GTO Preservation Project Rich Cummings Last edited by Rich69shortfleet; 01-21-2018 at 01:03 AM.

01-21-2018, 12:23 AM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,320	Re: Are the original Oil Pressure gauges mechanical - Not sure if you have checked into it that far yet but you will also have to swap some wires around in the wiring connector so you don't fry your fuel gauge. There are a few threads on the procedure.... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

01-21-2018, 01:25 AM	#5
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,703	Re: Are the original Oil Pressure gauges mechanical Here's one. http://67-72chevytrucks.com/vboard/s...d.php?t=588853 __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

01-21-2018, 01:37 AM	#6
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,703	Re: Are the original Oil Pressure gauges mechanical Here is a good thread on installing the battery gauge which has no wiring on a light gauge truck. http://67-72chevytrucks.com/vboard/s...d.php?t=393139 __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

01-21-2018, 01:48 AM	#7
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,561	Re: Are the original Oil Pressure gauges mechanical As far as the temp gauge part of the problem, the gauge cluster has both temp light and temp gauge. On gauge cluster trucks, the temp light is not wired and completely unused, but it's there and could be used. The sender for temp light and for temp gauge are different. Both are electric. The one for temp light is a switch, and the one for the gauge is variable resistance. Since you probably already have the sender for temp light, you could probably add the sender for temp gauge in the other head (got V-8?) and end up with both light and gauge working. As LockDoc mentions, you can't just remove a warning light cluster and plug in a gauge cluster using the same plug, you would need to re-arrange the wiring in the plug, so proceed with caution. You may also need to consider the generator warning light since the gauge cluster doesn't have one. I think the warning light may be necessary for proper voltage regulation, there are differences between the warning light trucks and gauge trucks that I don't understand when it comes to the alternator. The electrical questions forum is a good place to search and to ask for help. To connect the battery gauge, it has 2 wires. Both should have a 4 amp fuse near the point where you connect them to the wiring harness. One connects to the 12 gauge red wire that comes off the battery at the fusible link, and the other one connects to the same 12 gauge red wire at the junction near the driver side headlight where it splits to separate wires going to the alternator and to the cab. More info about the temperature senders: Gauge: It has been discussed before on other threads you can only use the stock 1/2" NPT threaded sender for the temp gauge if you have a stock instrument cluster. There is no 3/8" NPT sender that will work. If you have a 3/8" NPT threaded hole in the engine head, you can get a 1/2" sender and have a machinist turn and thread it to 3/8". I had forum member A1971Blazer turn and thread mine. Other people had it done by brian mac. I used GM part number 12334869, AC Delco number G1852. Light: If you change your engine and now have 3/8" instead of 1/2" NPT hole in the head and want to use the warning light, use Autozone Duralast or Wells part number TU78 for the sender. These are threads on the subject that I have bookmarked and used: http://67-72chevytrucks.com/vboard/s...d.php?t=490161 http://67-72chevytrucks.com/vboard/s...d.php?t=703388 http://67-72chevytrucks.com/vboard/s...d.php?t=627880 http://67-72chevytrucks.com/vboard/s...d.php?t=726025 Note: I see other have posted some good info for you while I was writing.

01-21-2018, 11:18 AM	#8
ZEKE68 Registered User Join Date: Jul 2012 Location: Space Coast, Florida Posts: 403	Re: Are the original Oil Pressure gauges mechanical I had planned to change the dash wiring harness to a gauge type harness if I went to the gauge panel. Good info about the warning light in the gauge panel as I want to keep warning lights for the oil pressure and water temp even if I go to a gauge panel. Two options are 1 go with the new gauge panel and new harness and add warning lights for oil and water, or 2 keep the warning light panel and add oil and water gauges below the dash. If I do option 2 I can use sending unit gauges for oil and water. I am not a big fan of oil lines running into the interior as I have had copper lines break and plastic lines get melted by an electrical short before. Both were messy. __________________ 1968 SWB Step Side, Big Block, 4L80E , Running!

01-21-2018, 01:21 PM	#9
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,561	Re: Are the original Oil Pressure gauges mechanical You probably could get an electric type oil gauge and sender and modify the stock instrument cluster to house it, although I think with new copper tubing it may be unlikely for you to have a mess so I would probably go that route. Having a generator and oil pressure warning lights on the stock gauge instrument cluster may be something you can work in as well. I think you would have to be somewhat skilled at fabrication to make it look period correct. On the gauge instrument cluster the center is where the optional tachometer goes, and you could swap in the generator and oil light panel there, but that panel also has the turn signal indicators that may look out of place. So perhaps mask those. You can put a little tach or a clock between the generator and oil lights and that would look nice. I think an ideal cluster would have all those things. The other thing I have considered is make a blinking circuit out of some small microchips and relays that would use the temp light to mean overheat when solid on, generator or oil problem when blinking. Sort of use it as a check engine light. And another option is to buy an aftermarket instrument cluster that is the type where you just pick a bunch of gauges and lights and install them wherever you wish. Some of those look nice.



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