OldsCutlass70

Been gone for 4 years, and now my Speedometer does not work.

(1970 Olds Cutlass "S")

Is there a fuse for this? I have been looking in the manual, but have had no luck as of yet.

I figured someone would know this one for sure.


Thanks in advance.

Robert

calicanuck66

are you talking the lights in it do not work, or the speedo needle itself is inop ??

The speedo is mechanical & drives off a cable that runs off the trans speedo gear that is located in the trans itself. As far as lights, there are a couple of small twist in/off bulbs that can be changed that are located on back of the speedo head itself.

OldsCutlass70

Well, it doesn't move or light up so perhaps it's both issues you mentioned. I am going to take a look inside tomorrow regarding the bulbs.

Hopefully that's a quick fix. Regarding the cable, is that an easy fix itself, or does it require removing the trans?

calicanuck66

Nope, no trans removal necessary. As long as the gear that is inside the trans turns, it may just be a siezed speedo cable (easy to replace speedo cable-just screws into speedo gear housing on trans & other end plugs into back of speedo head after going thru grommet on firewall)

Easy way to tell if speedo gear turns in trans., is to jack up front of car, chock front wheels, remove speedo cable from trans housing, put car in "N" gear, turn rear wheels by hand & see if speedo gear in trans. is turning.

You can check the cable operation while your at it down there as well. Inside the outer housing of speedo cable, is an inner square looking 2nd cable. If you turn the square shaped inner cable, & it spins, it should be making the speedo needle move up on the speedo head. (you will need 2nd person up top in car to see if speedo needle is moving while your underneath car)

I did have this prob once (TH400) & tried the above method. Found out that cable was ok, because after I unscrewed speedo cable off trans speedo gear housing, I spun the inner square cable & my speedo needle up top DID turn, & the gear in my trans was not. I loosened the trans speedo gear housing clamp & while turning the rear wheels by hand, I "clocked" the speedo gear housing on trans from side to side a bit & VOILA !! the trans speedo gear started to turn. It was just not sitting in the right position & the gears inside the trans that mesh with the speedo gear were not aligned properly

calicanuck66

I forgot to ask if the other gauge lights on dash work other than the speedo. I believe they are all on same circuit. If they do, & speedo doesn't, it may very well be that the little bulbs are burned out

OldsCutlass70

I need to check again, but I believe the engine light works but need to check again. I checked the fuse that said gauges, and it looks good.

Thanks for the info. I am going to print this, and make an attempt soon.

First thing indeed to do is replace my plugs. I was checking them today, and one came out easily by hand. That can never be good...

calicanuck66

the other thing i forgot to ask, is if your car has the factory cruise control option. if it does, then there are TWO speedo cables to check. An upper & lower one. My car isn't equipped with cruise, but some are...

jaunty75

You're confusing lights here. The lights that light up the dashboard and illuminate the gauges so you can see them at night are separate from the TEMP, GEN, OIL, and BRAKE lights as far as the circuitry that controls them. The indicator lights should go on when you're engaging the starter and stay off the rest of the time. If they do, there is nothing wrong with those bulbs or that circuitry. If they don't, you should remove the ones that don't work and test them or just replace them with known good bulbs. If they still don't work, then you will have to troubleshoot the circuits that control those indicator lights.

The dash/gauge illumination lights should go on whenever you pull out the headlight switch to the first stop. If NONE of the illumination lights light up when the headlight switch is pulled out, it's unlikely that they're all burned out, and you should the 4-amp fuse in the fuse panel that controls them.

If some of them work and some don't, then, as noted, the ones that don't are probably burned out. All of the indicator bulbs (TEMP, GEN, etc.) as well as the dash/gauge illumination bulbs are, as noted, screwed 1/4 turn into openings in the printed circuit that makes up the backside of the gauges. A service manual would be very helpful here as it would have a diagram of the printed circuit showing which bulbs are which. You can also just reach up under there, remove them one at a time, and test them.

As noted, there is no relationship between the speedometer and the lights that illuminate it as the speedometer is controlled entirely mechanically.

MDchanic

Engine light?

- Eric

OldsCutlass70

Thank you for clearing that up. I will get to that shortly, hopefully this afternoon.