I've just bought a '91 740 wagon and the only problem it seems to have is that the speedometer occasionally goes to 45 mph and stays there no matter hows fast I'm going. Then, without provocation. it works normally. Then it quits working altogether (drops to zero).

I'll appreciate any thoughts or suggestions.

Thanks,

Will Connelly

Hi Will,

I've been watching for speedo info for some time now, and I have in my posession 4 complete clusters as the end result of my efforts.

Question is - Does the odometer work properly? If so then you problem is likely in the speedo head itself, not in the Sending Unit, Instrument Cluster Ground or any other electrical problem on the Cluster Circut Board. Solution seems to be get another speedo head (wrecker, Volvo is many 100's), or get yours fixed (about $90US I've seen)

If your speedo and odometer are both going on/off or acting odd, then certainly check for the wiring and sending unit problems noted.

Good Luck

Greg
86 740 - Speedo in Miles/KMH (in Canada)with no Odometer (good enough)!

check the faq under instruments. I read about this happening there the other day, the spedometer in my 940 is giving me crap.

The faq said to look for a wire that was grounding out coming from the speed sensor on the rear end.

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My Volvo Page

My 91 740 did pretty much the same as yours except mine would go to 70 mph..be erratic at times till it finally quit. If your odometer is working ok then the sending unit (called a hall sensor, located in the differential is working fine....my speedo is electronic..
yours is probably electronic too..no cable on this one! I made a post many months ago and a feasable reply I received was from a gentleman in Malysia who
claimed to have dismantled a few of these units and his findings were that the failure of the speedo is due to a fried chip located on the speedos electrical board!!! AS to why the premature failure...he didnt say...nor a source for these
chips...so like you I am driving around with a broken speedo...cost of a new one...$500!!! not for the cluster ...just the speedo!!! AS an alternative
maybe a junk yard! Incidentally and for whats it s worth the speedo unit is japanese made...yamazki or yamaki ..something like that ...Good luck