This may have been posted to death but could not find a great answer on it. I have a 56 F100 that has been modified previously with @ a 68 289. I have gone through and rewired most of the truck and only left the starting\charging system in place (12V system). I made sure all wires were good with not bare places and replaced the starter, alt, voltage regulator etc. with correct (to the best of my and <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comffice:smarttags" /><st1:City w:st="on"><st1lace w:st="on">Napa</st1lace></st1:City>’s knowledge) parts. Here’s my issue: I’ve been running fine on the setup for a month or so and now all of a sudden the BATT light has come on and cannot figure out why. I’ve triple checked the wiring and made sure the alt was putting out (@ 14 V with a little gas on at battery). Have driven with all lights on etc and battery output remains good. Any ideas what I’m missing?
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Next question is the temp gauge – I have a stock 1956 12v temp gauge that is a pretty basic set-up (if I did it right). It has one hot wire running from new fuse block (hot when switch is turned on) and one running to temp sensor… When I turn it on the temp gauge falls all the way back to C – which is good. Problem is that it stays there – which is bad.
I’ve replaced sensor and actually bought another gauge that I “think” is ok functional wise. Was there something else in between the wiring I’m possibly missing?
Thanks

 

Hi and Welcome to FTE!

Well, lets start with the temp guage. As you indicated, wiring is simple: Power from a switched source to the gauge. Then out from the opposite lug on the gauge to the sending unit which is grounded to the block-or is it?

Did you use teflon tape in the threads or a thread sealer - no can do. Also is the sending unit the one matched to the 56 gauge or the 289 engine? You can't mix the two - it has to be a 56 sending unit not the 289 sender.

If the gauge is good and the simple wiring is correct with no shorts, the problem is either the correct sender, sender is not working correctly (are you sure it's down into the coolant and the engine is actually getting hot enough to register) or the sender is not properly grounded.

Well with the info you provided, I'd say the alternator is not putting out enough.

An alternator should be putting out more a dash than 14 volts. That's system/battery voltage. 14 is mimimum, but 14.5 to 15.5 is better.

Why people use voltage as a judge of positive charging is beyond me. Check to see how many AMPS the alternator is putting out, lights and heater motor on - 1500 rpm - 14 to 15.5 volts, should be at least 10-15 amps.

Initially sounds like it's not producing quite enough and the light is doing it's job.

 

Thanks for the great info... Good point on the ground on block - the old one was sealed in with some type of sealer (alot of it) so, I may not have got all of it out with my little wire thread cleaner. Will give that another good gong over and see how that goes.

I'm a little old school on the voltage - granddad owned a service station for 30 years and picked up the habit from him. I just like to throw it on as a quick check to make sure it's reading more than 12 volts. It is a new alt and I did have the amps tested the other day at advanced auto - just did not think to post. It's testing about 65 amps (what it's rated for) - not sure what else unless the regulator I bought has gone bad or just need to get a high output alt.

I don't like all the mixing on the truck just working on what I got

The volt reading is 14 at a low idle and a little higher with slight increase in RPMs... Will check the amps on batt when I can get another hand to work the gas while I look at the meter. Thanks again.

 

Well, withthat it sounds like the alternator is producing ok. It's curious that the light just started to come on. Stupid question, are you sure you have the wire running through the guage in the right direction?

And the power wiring flow is the same as for your old generator right?

 

Hi guys have a 1956 f100 272 engine. I have a problem with my temp gauge is always reading hot when I turn switch on it doesn't do anything I checked for power and is getting 12v from ignition switch when I ground the wire that comes from the sender it goes all the way to cold position but then when there is no ground it goes back to hot position no sure what is wrong I run the engine but nothing I doesn't move from hot position even is getting 12 v will try another sending unit but any help will be appreciated thanks

 

B6C-10884-A .. Temperature Sending Unit / 1956 only and was used in all 1956 FoMoCo vehicles.

It's obsolete and has been hard to find for many years, but I see that Carpenter has it listed in his 1948/56 truck repro parts catalog (2011 paper version): 60 bucks.

If you think that's expensive, I was getting 100 bucks 35 years ago at swap meets and in Hemmings, as I found 12 NOS at a dealer in NorCal.