Factory gages.

Discussion in 'Trucks and Trailers' started by KK, Feb 21, 2001.

  1. KK

    KK LawnSite Member
    Posts: 90

    I have factory gages on my '83 C20 and want to hook them up properly to the new Goodwrench engine that I'm working on. The water temp wasn't working right and I found that the wire going to the block sensor was disconnected. The oil pressure wasn't working either because it always registered 40psi even when the engine wasn't running! The questions I have are as follows: What do I need to get these fixed? Arent they electric and at the most need new sending units? or, are they kinda junky as they get old? Will sending units on the engine do it or do I need to look at the gages themselves in the dash? Thanks.
  2. Power mad

    Power mad LawnSite Member
    Posts: 72

    Hey KK
    The gages in the dash are electronic, and if every thing is working properly are pretty acurate.
    The sending unit for the oil is at the back of the block on top behind the intake manifold, drivers side.
    On a fresh engine I always replace the oil and water sending units.
    To see if the gage is woking properly, {with key on} ground the lead for the oil unit to the block. The gage should max out. If not then there is a problem with the gage or a circuit problem.
    It's also a good idea to have the gages in view so you can moniter the engine.
    If you decide to get mechanicle gages get a good set. Auto meter makes nice gages, kinda spendy but they're nice gages.
    See ya
  3. 9521

    9521 LawnSite Member
    Posts: 16

    Don't be surprised if the in dash gauges are bad. I've had this problem on two separate vehicles.

    Get some autometer mechanical gauges via ebay. The stock ones aren't accurate worth a hoot anyway.
  4. plowjockey

    plowjockey LawnSite Senior Member
    Posts: 332

    Power Mad

    I have an '80 C-70 dump and my oil pressure gauge is maxxed out all the time. It moves some times but it does not respond. Could, do you think, the problem be that the sending unit has shorted out?

  5. John DiMartino

    John DiMartino LawnSite Silver Member
    Posts: 2,555

    Plow jockry-unplug the sender-if it drops back to zero-the sender is bad-they go bad often,i wouldnt be surprised if it was bad.
  6. plowjockey

    plowjockey LawnSite Senior Member
    Posts: 332

    Thanks John

    When I shut it off the gauge goes down some but not to zero. When I turn it back on it maxxes out again. I'll try unplugging it tomorrow...I just took it back to its parking space.

    Thanks again.

  7. RTallday

    RTallday LawnSite Member
    Posts: 214

    Since we are all on the subject of oil gauges, does anyone know the color of the wire that is supposed to go from the gauge in the cluster to the sending unit? I have an aftermarket gauge, and i want to hook up the origional one. THEY ARE ACCURATE!!! They wouldn't have been put in the trucks to begin with if they werent accurate.


  8. 9521

    9521 LawnSite Member
    Posts: 16

    I guess we'd need to agree to disagree. My own experience has been different and I tend to place a stock gauge just one step above an idiot light. If yours is accurate, it's probably the exception to the rule.

    GM Fuel and Temp gauges are particularly known for only giving you a vague idea of what is happening - especially the small ones used with 40 gallon tanks which seem only accurate to within about 20%. The Oil gauges are a little better but tend to peg at above 50 PSI. In comparing the temp gauges in my K30, the stock gauge in the 11 o'clock position just short of 210 degress correllates with about 230 on the Autometer under the dash. Go figure. These problems are compounded when the gauges are calibrated with either L&H (low and high), C&H (cold and hot), etc. Again, not to say yours isn't on the money - maybe yours was made on a Wednesday and all mine have been made on Mondays and Fridays.... :eek:) but you probably wouldn't see so many aftermarket gauges in vehicles if the stock ones were accurate and reliable.

  9. plowjockey

    plowjockey LawnSite Senior Member
    Posts: 332

    My experience with GM gauges has been that they have been pretty accurate to other aftermarket gauges that I have tested over the last 30 or so years.

    By the way I work in a GM automotive plant and I do the best quality work of my ability EVERY day. I have more personal pride than that in what I do for a living and the customer deserves the best that I can put out. I think you are selling some very good people more than a little bit short.

    Sorry but that comment just struck a nerve.

  10. mike reeh

    mike reeh LawnSite Member
    Posts: 229

    about aftermarket guages reading diff than stock, are the sending units in different spots in the engine?? that would give a diff reading, also, if they're hooked to the same sending unit than its probably the wrong unit for at least one (if not both!) of the guages...

    ive had stock guages read pretty decently, but its always in untouched trucks.. ive seen a few suburbans, blazers and trucks that over the years have had literally everything broken, replaced, bypassed, etc, and who KNOWS what they've got in em and the guages are always funky... junkyard guage clusters, any old sending unit, etc.. its just a mess.. those are the guages that seem to give problems..


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