I have a problem, I just recently rebuilt a 1990 bronco 5.8. The truck runs great, but the temperature gauge doesn't work. I've replaced the sending unit, but that didn't do it. I'm running straight water, but will flush tommorow, get the crap out of the coolant system and replace with coolant. I tested the green wire on the wiring harness and only got 4-5 volts. Another thing that is not working is the horn. The relay is clicking on the horn, but no horns sound when the button is pushed. Any help would be greatly appreciated, thanks

 

did you install a 195 degree thermostate in the new motor? also the sending unit plug looks alot like another sensor that sits near the middle of the lower intake on the drivers side. if they were switched could cause what you are saying as well. but really now would be a good time to hook up a mechanical gauge an buy a haynes manual to make sure you messing with the correct sending unit.

 

Well last night I tried by just unhooking the positive battery terminal. didn't work. Where would I get a mechanical gauge, the only mechanical one I have is for testing oil pressures. Any help would be greatly appreciated.

 

any parts store will carry a mechanical water temp gauge. what would unhooking the battery do but clear the computer.

 

What Kem is saying is that the Mechanical gauge can be purchased to replace the electrical gauge that came with the truck. You can purchase a single gauge at an autoparts store or do what I did and purchased a set which included water temp, oil pressure and volts. The three mini-set gauge costs me about $50 (Equus brand). A single gauge can run anywhere between $12 and $50 depending on brand. These are VERY easy to install, should have their own instructions and like Kem said you might as well do it now while your working in there anyway. Oh and by the way...you do not need to take out the existing gauges, you will however need to find a place to mount them (gauge pod on the A-pillar or underneath the ashtray).

If you have problems installing just let us know! We can help!

Good luck bro!

 

I went to the parts store and looked at the gauges, but couldn't justify the $16 for the gauge and installing it(It is not my truck), so I decided to troubleshoot more. Come to find out the guy I talked to earlier sold me the wrong damn gauge. I was under the impression, from what he said, that there was only gauge on the truck. If I had read the posts in detail I would've understood that, to be wrong. Sorry if I ask a lot of stupid questions, because this is my first bronco to overhaul. I have done a lincoln, escort, E30 BMW(mine), and some work with a 90 4.0 ranger(mine).

 

A few things:
1) It's not your truck?
2) The mechanical gauge will give you a much more acurate reading of oil pressure than the stock gauge. If there is a short within the system it could cause your electrical gauge to either spike or fall...thereby causing you to think there is serious problem with the engine. I am very happy I have gone this route so know the exact functioning of my engine without having to hunt down electrical gremlins.
3) If it is anything like the 86 it has two sending units:
a) On mine one is located on the "octogon tree" above and behind the thermostat (passenger side of the engine). This sensor sends information back to the computer and the computer adjusts air, fuel, etc...accordingly. If this is not hoocked up your truck will run really rough...
b) The second sending unit is located on the driverside front of the blocknear the edge of the valve cover gasket (mine is a red wire, small boot that connects to a "pin" or plug looking thing). If this is not hooked up this will surely cause the gauge not to read the electrical signal....no gauge reading.
4) You said the guy sold you the wrong gauge...did you mean temp sending unit (sensor)?
5) All of your other gauges work? Did you re-check your grounds?

Keep us up to date!

 

It is my brother in laws truck. I got the electrical onbe to work. What I mean is the guy sold me the one for the computer not the gauge. I picked up the right one and now the gauge has a reading. Thanks for all the help, and I will mention the mechanical gauges to him. Also I am looking for a bronco. I'm looking for one that somebody wants to dump, with mechanical issues. When I bought the lincoln it had blown headgaskets. I bought it for $200. Pretty sweet deal I would say.

 

SWEET!